@article{jones_dunne_cahoon_jennings_leon_everman_2024, title={Confirmation and inheritance of glufosinate resistance in an Amaranthus palmeri population from North Carolina}, url={https://doi.org/10.1002/pei3.10154}, DOI={10.1002/pei3.10154}, abstractNote={A putative glufosinate-resistant}, journal={Plant-Environment Interactions}, author={Jones, Eric A. L. and Dunne, Jeffrey C. and Cahoon, Charles W. and Jennings, Katherine M. and Leon, Ramon G. and Everman, Wesley J.}, year={2024}, month={Jun} }
 @article{leon_bennett_chandra_2024, title={Development of <i>Brassica carinata</i> A. Braun resistant to acetolactate synthase-inhibiting herbicides}, volume={10}, ISSN={["1435-0653"]}, url={https://doi.org/10.1002/csc2.21391}, DOI={10.1002/csc2.21391}, abstractNote={Abstract Brassica carinata A. Braun (carinata) has become an important oil crop for biofuel production in subtropical regions. Carinata is highly sensitive to acetolactate synthase (ALS)‐inhibiting herbicides, limiting its introduction into existing crop rotations. The objective of the study was to develop carinata lines resistant to ALS‐inhibiting herbicides. A susceptible carinata line was crossed with a resistant Brassica napus L. line. Lines derived from those crosses were screened at high doses of imidazolinones, which allowed identifying five lines with high levels of resistance. Doses to reduce plant growth 50% (GR 50 ) and cause 50% injury (ID 50 ) were four to nine times greater than susceptible lines. Resistant lines exhibited cross resistance with halosulfuron (sulfonylurea). Resistance was confirmed under field conditions with doses 2X and 4X for imazethapyr and 4X–8X for halosulfuron of their respective label doses. While susceptible lines died, resistant lines exhibited no injury or growth reductions compared with nontreated controls. Sequencing of the ALS gene indicated that all resistant lines carried a Trp574Leu amino acid substitution, a mutation responsible for resistance in other species. Crosses between resistant lines and a susceptible line demonstrated that the inheritance of the mutation corresponded with the resistance phenotype in the F2. The resistance trait behaved as a single, fully dominant allele, which makes it easier to transfer it to carinata lines with desirable agronomic traits. The resistant lines developed here provide flexibility for use in multiple crop rotations and opens the possibility to use ALS‐inhibiting herbicides for weed control within this crop's growing season.}, journal={CROP SCIENCE}, author={Leon, Ramon G. and Bennett, Rick and Chandra, Saket}, year={2024}, month={Oct} }
 @article{huddell_needelman_law_ackroyd_bagavathiannan_bradley_davis_evans_everman_flessner_et al._2024, title={Early-season biomass and weather enable robust cereal rye cover crop biomass predictions}, volume={9}, ISSN={["2471-9625"]}, DOI={10.1002/ael2.20121}, abstractNote={AbstractFarmers need accurate estimates of winter cover crop biomass to make informed decisions on termination timing or to estimate potential release of nitrogen from cover crop residues to subsequent cash crops. Utilizing data from an extensive experiment across 11 states from 2016 to 2020, this study explores the most reliable predictors for determining cereal rye cover crop biomass at the time of termination. Our findings demonstrate a strong relationship between early‐season and late‐season cover crop biomass. Employing a random forest model, we predicted late‐season cereal rye biomass with a margin of error of approximately 1,000 kg ha−1 based on early‐season biomass, growing degree days, cereal rye planting and termination dates, photosynthetically active radiation, precipitation, and site coordinates as predictors. Our results suggest that similar modeling approaches could be combined with remotely sensed early‐season biomass estimations to improve the accuracy of predicting winter cover crop biomass at termination for decision support tools.Core Ideas
Cereal rye winter cover crop biomass modeled on data from 35 site‐years.
We found a strong relationship between early and late‐season biomass.
Random forest model with early‐season biomass and weather data performed well.
Similar approach could improve decision support tools for cover crop management.
}, number={1}, journal={AGRICULTURAL & ENVIRONMENTAL LETTERS}, author={Huddell, Alexandra and Needelman, Brian and Law, Eugene P. and Ackroyd, Victoria J. and Bagavathiannan, Muthukumar V. and Bradley, Kevin and Davis, Adam S. and Evans, Jeffery A. and Everman, Wesley Jay and Flessner, Michael and et al.}, year={2024}, month={Jun} }
 @article{jones_bradshaw_contreras_cahoon jr_jennings_leon_everman_2024, title={Growth and fecundity of Palmer amaranth escaping glufosinate in cotton with and without grass competition}, volume={38}, ISSN={["1550-2740"]}, DOI={10.1017/wet.2024.68}, abstractNote={Abstract Field experiments were conducted at Clayton and Rocky Mount, North Carolina, during the summer of 2020 to determine the growth and fecundity of Palmer amaranth plants that survived glufosinate with and without grass competition in cotton. Glufosinate (590 g ai ha -1 ) was applied to Palmer amaranth early postemergence (5 cm tall), mid postemergence (7 to 10 cm tall), and late postemergence (>10 cm tall) and at orthogonal combinations of those timings. Non-treated Palmer amaranth was grown in weedy, weed-free in-crop (WFIC) and weed-free fallow (WFNC) conditions for comparisons. Palmer amaranth control decreased as larger plants were treated; no plants survived the sequential glufosinate applications in both experiments. The apical and circumferential growth of Palmer amaranth surviving glufosinate treatments was reduced by more than 44% compared to the WFIC and WFNC Palmer amaranth in both experiments. The biomass of Palmer amaranth plants surviving glufosinate was reduced by more than 62% when compared with the WFIC and WFNC in all experiments. The fecundity of Palmer amaranth surviving glufosinate treatments was reduced by more than 73% compared to WFNC Palmer amaranth in all experiments. Remarkably, the plants that survived glufosinate were fecund as WFIC plants only in the Grass Competition experiment. The results prove that despite decreased vegetative growth of Palmer amaranth surviving glufosinate treatment, plants remain fecund and can be fecund as non-treated plants in cotton. These results suggest that a glufosinate-treated grass weed may not have a significant interspecific competition effect on Palmer amaranth that survives glufosinate. Glufosinate should be applied to 5 to 7 cm Palmer amaranth to cease vegetative and reproductive capacities.}, journal={WEED TECHNOLOGY}, author={Jones, Eric A. L. and Bradshaw, Colden L. and Contreras, Diego J. and Cahoon Jr, Charles W. and Jennings, Katherine M. and Leon, Ramon G. and Everman, Wesley J.}, year={2024}, month={Oct} }
 @article{jones_bradshaw_contreras_cahoon jr_jennings_leon_everman_2024, title={Growth and fecundity of Palmer amaranth escaping glufosinate in soybean with and without grass competition}, volume={38}, ISSN={["1550-2740"]}, DOI={10.1017/wet.2024.29}, abstractNote={Abstract Field experiments were conducted at Clayton and Rocky Mount, North Carolina, during the summer of 2020 to determine the growth and fecundity of Palmer amaranth plants surviving glufosinate with and without grass competition in soybean. Glufosinate (590 g ai ha -1 ) was applied at early postemergence (5 cm Palmer amaranth height), mid-postemergence (7-10 cm), and late postemergence (>10 cm) and at orthogonal combinations of those timings. Non-treated Palmer amaranth was grown in weedy (i.e., intraspecific and grass competition), weed-free in-crop (WFIC), and weed-free fallow (WFNC) conditions for comparisons. No Palmer amaranth plants survived the sequential glufosinate applications and control decreased as the plants were treated at a larger size for both experiments. The apical and circumference growth rate of Palmer amaranth surviving glufosinate was reduced by more than 44% when compared to the WFNC Palmer amaranth. The biomass of Palmer amaranth plants surviving glufosinate was reduced by more than 87% when compared to the WFNC Palmer amaranth. The fecundity of Palmer amaranth surviving glufosinate was reduced by more than 70% when compared to WFNC Palmer amaranth. Palmer amaranth surviving glufosinate were as fecund as the WFIC Palmer amaranth in both experiments for soybean. The results prove that despite the significant vegetative growth rate decrease of Palmer amaranth surviving glufosinate, plants can be fecund as non-treated plants in soybean. The trends of growth and fecundity of Palmer amaranth surviving glufosinate with and without grass competition were similar. These results suggest that glufosinate-treated grass weeds may not reduce the growth or fecundity of Palmer amaranth surviving glufosinate.}, journal={WEED TECHNOLOGY}, author={Jones, Eric A. L. and Bradshaw, Colden L. and Contreras, Diego J. and Cahoon Jr, Charles W. and Jennings, Katherine M. and Leon, Ramon G. and Everman, Wesley J.}, year={2024}, month={May} }
 @article{cahoon_jordan_tranel_york_riggins_seagroves_inman_everman_leon_2024, title={Influence of gender and glyphosate resistance on Palmer amaranth growth and interference with cotton}, volume={10}, ISSN={["2374-3832"]}, url={https://doi.org/10.1002/cft2.20272}, DOI={10.1002/cft2.20272}, abstractNote={Abstract Management of herbicide‐resistant weeds can be improved by understanding the biology of resistant biotypes. While the majority of research has focused on female plants and seed production of Palmer amaranth ( Amaranthus palmeri S. Watson) that are resistant to glyphosate, growth of male plants that are resistant to this herbicide has not been studied in detail. Additionally, interference of male versus female Palmer amaranth plants on cotton ( Gossypium hirsutum ) yield has not been reported. Plant height and biomass of male and female plants from a mixed population of glyphosate‐resistant (GR) and glyphosate‐susceptible (GS) plants was studied in North Carolina when grown season‐long with cotton. Palmer amaranth height was less for GR male plants compared with GS males and both GR and GS females. Biomass of Palmer amaranth female plants was twice that of male plants irrespective of glyphosate resistance. Cotton yield was affected similarly by Palmer amaranth regardless of either gender or glyphosate resistance status. The implications of shorter GR male plants on pollen dispersal and ramifications on management of glyphosate resistance are not known. Results from these trials did not address implications of the height of male plants on fitness of GR resistance. Nonetheless, the finding that GR male plants were shorter in the field than GS male plants warrants a new look at this topic. Similar reductions for cotton yield in presence of both GR and GS biotypes and genders suggest that current yield loss assessments and management decisions do not need to consider these variables in Palmer amaranth populations.}, number={1}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, author={Cahoon, Charles W. and Jordan, David L. and Tranel, Patrick J. and York, Alan C. and Riggins, Chance and Seagroves, Richard and Inman, Matthew and Everman, Wesley and Leon, Ramon}, year={2024}, month={Jun} }
 @article{dobbs_goldsmith_ginn_skovsen_bagavathiannan_mirsky_reberg-horton_leon_2024, title={Mapping predicted biomass in cereal rye using 3D imaging and geostatistics}, volume={10}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2024.62}, DOI={10.1017/wsc.2024.62}, abstractNote={Abstract Cover crops are becoming an increasingly important tool for weed suppression. Biomass production in cover crops is one of the most important predictors of weed suppressive ability. A significant challenge for growers is that cover crop growth can be patchy within fields, making biomass estimation difficult. This study tested ground-based structure-from-motion (SfM) for estimating and mapping cereal rye ( Secale cereale L.) biomass. SfM generated 3D point clouds from red, green, and blue (RGB) videos collected by a handheld GoPro camera over five fields in North Carolina during the 2022 to 2023 winter season. A model for predicting biomass was generated by relating measured biomass at termination using a density–height index (DH) from point cloud pixel density multiplied by crop height. Overall biomass ranged from 320 to 9,200 kg ha −1 , and crop height ranged from 10 to 120 cm. Measured biomass at termination was linearly related to DH (r 2 = 0.813) through levels of 9,000 kg ha −1 . Based on independent data validation, predicted biomass and measured biomass were linearly related (r 2 = 0.713). In the field maps generated by kriging, measured biomass data were autocorrelated at a range of 5.4 to 42.2 m, and predicted biomass data were autocorrelated at a range of 3.4 to 12.0 m. However, the spatial arrangement of high- and low-performing areas was similar for predicted and measured biomass, particularly in fields with greatest patchiness and spatial correlation in biomass values. This study provides proof-of-concept that ground-based SfM can potentially be used to nondestructively estimate and map cover crop biomass production and identify low-performing areas at higher risk for weed pressure and escapes.}, journal={WEED SCIENCE}, author={Dobbs, April M. and Goldsmith, Avi S. and Ginn, Daniel and Skovsen, Soren Kelstrup and Bagavathiannan, Muthukumar V. and Mirsky, Steven B. and Reberg-Horton, Chris S. and Leon, Ramon G.}, year={2024}, month={Oct} }
 @article{laat_leon_dale_gouveia_carbajal_schiavon_unruh_iannone iii_milla-lewis_2024, title={Molecular analysis of St. Augustinegrass cultivar mixtures composition over time and latitude}, volume={9}, ISSN={["1435-0653"]}, url={https://doi.org/10.1002/csc2.21370}, DOI={10.1002/csc2.21370}, abstractNote={Abstract St. Augustinegrass [ Stenotaphrum secundatum (Walt.) Kuntze] is commonly planted in residential and commercial landscapes as a cultivar monoculture predisposing this lawn to pest invasion and high‐maintenance inputs. Researchers have suggested that increasing genetic diversity by growing cultivars in mixtures may increase turfgrass stress resilience. However, the stability and uniformity of those mixtures has not been studied. The present study was carried out to evaluate the stability of St. Augustinegrass cultivars mixtures over time and across three latitudes. The study was conducted in Citra and Fort Lauderdale, FL, and Jackson Springs, NC. Simple‐sequence repeats markers were used to genotype leaf samples of St. Augustinegrass cultivars planted in two‐ and four‐cultivar mixtures. Leaf samples were collected 1 and 3 years after establishment. In all locations, cultivar richness and evenness declined over time. Similarly, the relative abundance of the least persistent cultivars decreased approximately 50%–100% depending on cultivar and location. Differences in growth patterns among cultivars resulted in cultivar displacement and the predominance of a single cultivar. Cultivars that covered the ground faster or formed dense canopies early after establishment were dominant at the end of the study. Locally developed cultivars tended to be more dominant in their original latitude. The use of cultivar mixtures may help the identification of vigorous, competitive, and stress tolerant cultivars in turfgrass breeding programs. However, their commercial use remains challenging as if the patterns observed here for 3 years are representative of a continuous trend, and they do not persist over time.}, journal={CROP SCIENCE}, author={Laat, Rocio and Leon, Ramon G. and Dale, Adam G. and Gouveia, Beatriz and Carbajal, Esdras M. and Schiavon, Marco and Unruh, J. Bryan and Iannone III, Basil and Milla-Lewis, Susana R.}, year={2024}, month={Sep} }
 @article{leon_2024, title={Resistance or tolerance: distinction without a difference}, volume={1}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2023.80}, DOI={10.1017/wsc.2023.80}, abstractNote={An abstract is not available for this content. As you have access to this content, full HTML content is provided on this page. A PDF of this content is also available in through the 'Save PDF' action button.}, journal={WEED SCIENCE}, author={Leon, Ramon G.}, year={2024}, month={Jan} }
 @article{kulesza_leon_sosinski_kilroy_meis_castillo_wilson_2024, title={Risk of weed seed and seedling emergence from poultry litter}, volume={7}, ISSN={["2639-6696"]}, url={https://doi.org/10.1002/agg2.20479}, DOI={10.1002/agg2.20479}, abstractNote={AbstractIn areas surrounding large poultry industries, poultry litter is often an alternative nitrogen fertilizer for crop production. However, farmers who have not used poultry litter in the past have concerns regarding potential weed seed contamination. A survey was conducted to determine the occurrence of germinable weed seed in poultry litters (n = 61) submitted by growers and industry representatives across North Carolina. In a 9:1 potting media:poultry litter mix, a single grass seed germinated from the 61 surveyed poultry litters, equating to 0.3 viable seeds 100 g−1 poultry litter. Viable seed content averaged 1.1 seeds 100 g−1 litter using the extractable seedbank method on 25% of the litters from the survey, much higher than the grow out method, and the majority of seeds found were Amaranthaceae. A growth chamber experiment was then conducted and demonstrated that there was a negative relation between poultry litter application and weed seedling emergence. There was a 65%, 75%, and 85% reduction in Senna obtusifolia (L.) H.S. Irwin & Barneby, Setaria pumila (Poir.) Roem. & Schult., and Amaranthus palmeri S. Watson germination, respectively, from the control to highest application rate of poultry litter (26.9 Mg ha−1). A laboratory study showed that poultry litter leachates can decrease seed radicle length and integrity and is likely due to osmotic or salinity stress. The weed seed content in litter as well as the negative impact of poultry litter and its leachates on weed seedling emergence make it unlikely that poultry litter applications will significantly increase seedbanks above levels commonly observed in agricultural fields.}, number={1}, journal={AGROSYSTEMS GEOSCIENCES & ENVIRONMENT}, author={Kulesza, Stephanie B. and Leon, Ramon G. and Sosinski, Stephanie C. and Kilroy, Grace M. and Meis, Brittani and Castillo, Miguel S. and Wilson, Melissa L.}, year={2024}, month={Mar} }
 @article{huddell_thapa_marcillo_abendroth_ackroyd_armstrong_asmita_bagavathiannan_balkcom_basche_et al._2024, title={US cereal rye winter cover crop growth database}, volume={11}, ISSN={["2052-4463"]}, DOI={10.1038/s41597-024-02996-9}, abstractNote={AbstractWinter cover crop performance metrics (i.e., vegetative biomass quantity and quality) affect ecosystem services provisions, but they vary widely due to differences in agronomic practices, soil properties, and climate. Cereal rye (Secale cereale) is the most common winter cover crop in the United States due to its winter hardiness, low seed cost, and high biomass production. We compiled data on cereal rye winter cover crop performance metrics, agronomic practices, and soil properties across the eastern half of the United States. The dataset includes a total of 5,695 cereal rye biomass observations across 208 site-years between 2001–2022 and encompasses a wide range of agronomic, soils, and climate conditions. Cereal rye biomass values had a mean of 3,428 kg ha−1, a median of 2,458 kg ha−1, and a standard deviation of 3,163 kg ha−1. The data can be used for empirical analyses, to calibrate, validate, and evaluate process-based models, and to develop decision support tools for management and policy decisions.}, number={1}, journal={SCIENTIFIC DATA}, author={Huddell, Alexandra M. and Thapa, Resham and Marcillo, Guillermo S. and Abendroth, Lori J. and Ackroyd, Victoria J. and Armstrong, Shalamar D. and Asmita, Gautam and Bagavathiannan, Muthukumar V. and Balkcom, Kipling S. and Basche, Andrea and et al.}, year={2024}, month={Feb} }
 @article{oreja_arthur_bolfrey-arku_mochiah_klutse_yorke_hukporti_dzomeku_mahama_nboyine_et al._2024, title={Weed community differences in row crops with varying input levels in Ghana}, volume={10}, ISSN={["1550-2759"]}, DOI={10.1017/wsc.2024.51}, abstractNote={Abstract Peanut ( Arachis hypogaea L.) and maize ( Zea mays L.) are essential crops for Ghana’s economy and food security, but weed infestation poses a significant threat to their cultivation. Crop rotations influence weed communities, but little is known about these processes in peanut-cropping systems in West Africa. This study investigated the impact of different crop rotations and input levels on weed communities in Ghana over 3 yr. Results showed that low inputs (absence of herbicide and fertilization) favored species richness, while higher input levels (weed control with herbicides and fertilizer use) reduced it. Diversity and evenness were also affected by inputs, with varying patterns across locations and seasons. Weed population growth rates (λ) varied significantly by location and treatment; all management programs resulted in increasing weed populations. Principal component analysis revealed distinct associations between weed species and crop management. The majority of weed species exhibited a generalist behavior and did not associate with a particular management. However, billygoat weed ( Ageratum conyzoides L.) and Benghal dayflower ( Commelina benghalensis L.) were positively associated with high-input systems, while purple nutsedge ( Cyperus rotundus L.) exhibited strong associations with low and medium inputs. The weed–crop rotation dynamics described here demonstrate how management drives the selection of weed species that are more pervasive and interfere with important food crops in Ghanaian agriculture.}, journal={WEED SCIENCE}, author={Oreja, Fernando H. and Arthur, Stephen and Bolfrey-Arku, Grace and Mochiah, Moses B. and Klutse, Victoria and Yorke, Maxwell and Hukporti, Solomon and Dzomeku, Israel K. and Mahama, Georgie Y. and Nboyine, Jerry A. and et al.}, year={2024}, month={Oct} }
 @article{brainard_haramoto_leon_kells_van wychen_devkota_jugulam_barney_2023, title={A survey of weed research priorities: key findings and future directions}, volume={71}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2023.24}, DOI={10.1017/wsc.2023.24}, abstractNote={AbstractWe conducted an online survey of weed scientists in the United States and Canada to (1) identify research topics perceived to be important for advancing weed science in the next 5 to 10 years and (2) gain insight into potential gaps in current expertise and funding sources needed to address those priorities. Respondents were asked to prioritize nine broad research areas, as well as 5 to 10 subcategories within each of the broad areas. We received 475 responses, with the majority affiliated with academic institutions (55%) and working in cash crop (agronomic or horticultural) study systems (69%). Results from this survey provide valuable discussion points for policy makers, funding agencies, and academic institutions when allocating resources for weed science research. Notably, our survey reveals a strong prioritization of Cultural and Preventative Weed Management (CPWM) as well as the emerging area of Precision Weed Management and Robotics (PWMR). Although Herbicides remain a high-priority research area, continuing challenges necessitating integrated, nonchemical tactics (e.g., herbicide resistance) and emerging opportunities (e.g., robotics) are reflected in our survey results. Despite previous calls for greater understanding and application of weed biology and ecology in weed research, as well as recent calls for greater integration of social science perspectives to address weed management challenges, these areas were ranked considerably lower than those focused more directly on weed management. Our survey also identified a potential mismatch between research priorities and expertise in several areas, including CPWM, PWMR, and Weed Genomics, suggesting that these topics should be prime targets for expanded training and collaboration. Finally, our survey suggests an increasing reliance on private sector funding for research, raising concerns about our discipline’s capacity to address important research priority areas that lack clear private sector incentives for investment.}, number={4}, journal={WEED SCIENCE}, author={Brainard, Daniel C. and Haramoto, Erin R. and Leon, Ramon G. and Kells, James J. and Van Wychen, Lee R. and Devkota, Pratap and Jugulam, Mithila and Barney, Jacob N.}, year={2023}, month={Jul}, pages={330–343} }
 @article{leon_oreja_mirsky_reberg-horton_2023, title={Addressing biases in replacement series: the importance of reference density selection for interpretation of competition outcomes}, volume={10}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2023.53}, DOI={10.1017/wsc.2023.53}, abstractNote={AbstractReplacement series are used by researchers to understand how competition-related variables influence dynamics from the individual to the population and community levels, but this approach has been criticized because of inherent biases associated with plant size differences and density-dependent responses. The use of functional densities instead of demographic densities was proposed to minimize those biases. This work explored three models to determine reference densities for replacement series experiments based on (1) maximum biomass, (2) biomass at onset of diminishing returns (i.e., inflection point), and (3) nitrogen (N)-uptake equivalency. Replacement series experiments were conducted using redroot pigweed (Amaranthus hybridus L.):maize (Zea mays L.) and giant foxtail (Setaria faberi Herrm.):maize proportions of 1:0, 0.75:0.25, 0.5:0.5, 0.25:0.75, and 0:1. The monoculture density for each species was established according to the three models. Density selection criteria resulted in major differences in competitive interactions between species. The use of functional densities at which the biomass accumulation inflection point for the smaller species allowed both species to exhibit either increases or decreases in biomass production depending on competitive interactions for all interspecific mixtures. Conversely, the maximum biomass model favored the larger species, almost completely inhibiting the growth of the smaller species, which resulted in a poor characterization of competitive responses of the smaller species. The N uptake equivalency model resulted in interactions closer to the predicted neutral competition. The model based on the biomass accumulation inflection point was the most sensitive and informative across all interspecific mixtures for both species. We propose that to reduce bias associated with species size differences when determining reference densities for replacement series experiments, at least two criteria must be met: (1) the experiment sensitivity allows measuring and quantifying the competitive responses for both species in all mixtures, and (2) the balance between density and carrying capacity of the system minimizes intraspecific competition.}, journal={WEED SCIENCE}, author={Leon, Ramon G. and Oreja, Fernando H. and Mirsky, Steven B. and Reberg-Horton, Chris}, year={2023}, month={Oct} }
 @article{iboyi_mulvaney_leon_balkcom_bashyal_perondi_noia_devkota_small_2023, title={Brassica carinata physiological response to land preparation method and seeding rate}, volume={1}, ISSN={["1542-7536"]}, DOI={10.1080/15427528.2022.2163950}, abstractNote={ABSTRACT Best management practices that optimize agronomic performance and make Brassica carinata production compatible with existing cropping systems are crucial for the establishment of a carinata supply chain in the southeastern United States. To this end, research was carried out to quantify land preparation method (conventional, no-till, broadcast-disc, and ripper-roller) and seeding rate effects on (1.12, 5.60, 10.09, and 14.57 kg seed ha−1) on B. carinata physiology, yield, and seed chemical composition. Data were collected on days to 50% flowering; canopy cover; gaseous exchange parameters (leaf net photosynthesis, stomatal conductance, transpiration, intercellular CO2, and water use efficiency); leaf area index; root weight; shoot weight; aboveground biomass; yield; and seed chemical composition. Leaf net photosynthesis was affected by land preparation treatment, being greater under the ripper-roller treatment, particularly during bolting. On the other hand, a decrease in photosynthesis, stomatal conductance, and water use efficiency was observed as seeding rate increased, especially during bolting. Carinata seed under the ripper-roller land preparation had the greatest oil content but lowest glucosinolates and protein contents. Yield did not respond to land preparation. Yield was minimized (732 kg seed ha−1) at the 1.12 kg ha−1 seeding rate and maximized (1087 kg seed ha−1) at the 5.6 kg ha−1 seeding rate. No land preparation by seeding rate interaction was observed for gas exchange parameters and LAI during any of the growth stages, nor was any interaction observed for yield. Carinata’s physiological response to seeding rate did not depend on land preparation method employed.}, journal={JOURNAL OF CROP IMPROVEMENT}, author={Iboyi, Joseph E. and Mulvaney, Michael J. and Leon, Ramon G. and Balkcom, Kipling S. and Bashyal, Mahesh and Perondi, Daniel and Noia, Rogerio de S., Jr. and Devkota, Pratap and Small, Ian M.}, year={2023}, month={Jan} }
 @article{rebong_henriquez inoa_moore_reberg-horton_mirsky_murphy_leon_2023, title={Breeding allelopathy in cereal rye for weed suppression}, volume={11}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2023.64}, DOI={10.1017/wsc.2023.64}, abstractNote={AbstractRapid increase in the hectarage and agricultural systems that use cover cropping for soil conservation and improvement, soil moisture retention, and weed management has highlighted the need to develop formal breeding programs for cover crop species. Cereal rye (Secale cereale L.) is preferred by many growers due to high biomass production and weed-suppression potential, which is believed to be partially due to allelopathy. Rye germplasm exhibits large variability in allelopathic activity, which could be used to breed rye with enhanced weed suppression. Here, we provide an overview of rye history and breeding and describe a strategy to develop rye lines with increased allelopathic activity. The discussion focuses on ways to deal with important challenges to achieving this goal, including obligate cross-pollination and its consequent high segregation levels and the need to quantify allelopathic activity under field conditions. This review seeks to encourage weed scientists to collaborate with plant breeders and promote the development of cover crop cultivars better suited to reduce weed populations.}, journal={WEED SCIENCE}, author={Rebong, Democrito and Henriquez Inoa, Shannon and Moore, Virginia M. and Reberg-Horton, S. Chris and Mirsky, Steven and Murphy, J. Paul and Leon, Ramon G.}, year={2023}, month={Nov} }
 @article{ethridge_chandra_locke_everman_jordan_owen_leon_2023, title={Changes in the herbicide sensitivity and competitive ability of <i>Abutilon theophrasti</i> over 28 years: Implications for hormesis and weed evolution}, volume={79}, ISSN={1526-498X 1526-4998}, url={http://dx.doi.org/10.1002/ps.7604}, DOI={10.1002/ps.7604}, abstractNote={AbstractBACKGROUNDThe potential of weed species to respond to selection forces affecting the evolution of weedy traits such as competitive ability is poorly understood. This research characterized evolutionary growth changes in a single Abutilon theophrasti Medik. population comparing multiple generations collected from 1988 to 2016. A competition study was performed to understand changes in competitive ability, and a herbicide dose–response study was carried out to assess changes in sensitivity to acetolactate synthase‐inhibiting herbicides and glyphosate over time.RESULTSWhen grown in monoculture, A. theophrasti biomass production per plant increased steadily across year‐lines while leaf number decreased. In replacement experiments, A. theophrasti plants from newer year‐lines were more competitive and produced more biomass and leaf area than the oldest year‐line. No clear differences in sensitivity to imazamox were observed among year‐lines. However, starting in 1995, this A. theophrasti population exhibited a progressive increase in growth in response to a sublethal dose of glyphosate (52 g a.e. ha−1), with the 2009 and 2016 year‐lines having more than 50% higher biomass than the nontreated control.CONCLUSIONThis study demonstrates that weeds can rapidly evolve increased competitive ability. Furthermore, the results indicate the possibility of changes in glyphosate hormesis over time. These results highlight the importance of the role that rapid (i.e., subdecadal) evolution of growth traits might have on the sustainability of weed management strategies. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.}, number={10}, journal={Pest Management Science}, publisher={Wiley}, author={Ethridge, Sandra R. and Chandra, Saket and Locke, Anna M. and Everman, Wesley J. and Jordan, David L. and Owen, Micheal D.K. and Leon, Ramon G.}, year={2023}, month={Jun}, pages={4048–4056} }
 @article{jones_andres_dunne_leon_everman_2023, title={Confirmation and detection of novel acetolactate synthase- and protoporphyrinogen oxidase–inhibiting herbicide-resistant redroot pigweed (Amaranthus retroflexus) populations in North Carolina}, url={https://doi.org/10.1017/wsc.2023.4}, DOI={10.1017/wsc.2023.4}, abstractNote={AbstractComplaints of control failures with acetolactate synthase (ALS)- and protoporphyrinogen oxidase (PPO)-inhibiting herbicides on redroot pigweed (Amaranthus retroflexus L.) were reported in conventional soybean [Glycine max (L.) Merr.] fields in North Carolina. Greenhouse dose–response assays confirmed that the Camden County and Pasquotank County populations were less sensitive to ALS- and PPO-inhibiting herbicides compared with susceptible A. retroflexus populations, suggesting the evolution of resistance to these herbicides. Sanger sequencing of target genes determined the Camden County population carried a Trp-574-Leu mutation in the ALS gene and an Arg-98-Gly mutation in the PPX2 gene, while the Pasquotank County population carried a His-197-Pro mutation in the ALS gene (first documentation of the mutation in the Amaranthus genus), but no mutation was detected in the PPX2 gene. Single-nucleotide polymorphism (SNP) genotyping assays were developed to enable efficient screening of future control failures in order to limit the spread of these herbicide-resistant populations. In addition, preliminary testing of these assays revealed the three mutations were ubiquitous in the respective populations. These two populations represent the first confirmed cases of PPO-inhibiting herbicide-resistant A. retroflexus in the United States, as well as the first confirmed cases of this particular herbicide-resistance profile in A. retroflexus inhabiting North America. While no mutation was found in the PPX2 gene of the Pasquotank County population, we suggest that this population has evolved resistance to PPO-inhibiting herbicides, but the mechanism of resistance is to be determined.}, journal={Weed Science}, author={Jones, Eric A. L. and Andres, Ryan J. and Dunne, Jeffrey C. and Leon, Ramon G. and Everman, Wesley J.}, year={2023}, month={Mar} }
 @article{jones_andres_owen_dunne_contreras_cahoon_jennings_leon_everman_2023, title={Confirmation of a five-way herbicide-resistant Amaranthus tuberculatus population in North Carolina}, volume={7}, ISSN={["1365-3180"]}, url={https://doi.org/10.1111/wre.12590}, DOI={10.1111/wre.12590}, abstractNote={AbstractAmaranthus tuberculatus (waterhemp) is a pervasive weed of the Mid‐west and ‐south United States and is not native to North Carolina but infestations in crop fields have been reported recently. Amaranthus tuberculatus has evolved resistance to seven herbicide groups and multiple herbicide‐resistant populations are common where the species is native. The reported A. tuberculatus infestations in North Carolina have not been controlled with herbicides but no formal herbicide resistance characterisation has been conducted to date. Glasshouse dose–response experiments were conducted to determine the susceptibility of a population collected from Surry County, North Carolina to commonly applied postemergence herbicides compared to a herbicide‐susceptible population collected from Story County, Iowa. The Surry County population survived labelled rates of imazethapyr, atrazine, glyphosate, fomesafen, and mesotrione; the Story County population was controlled with these herbicides. Further, 2,4‐D, dicamba, and glufosinate effectively controlled the Surry and Story County populations. Molecular sequencing assays were subsequently conducted to determine if altered target sites facilitated resistance in the acetolactate synthase (ALS), 5‐enolpyruvylshikimate‐3‐phosphate synthase (EPSPS), photosystem II (psbA), and protoporphyrinogen oxidase (PPX2) genes. The Surry County population carried a Trp574Leu and ∆Gly210 mutations in the ALS and PPX2 gene, respectively. No mutations that would confer resistance were found in the EPSPS or psbA gene for either population. The results of both experiments provide evidence that a five‐way herbicide‐resistant A. tuberculatus population has encroached North Carolina. More research is needed to determine the mechanisms of resistance to atrazine, glyphosate, and mesotrione.}, journal={WEED RESEARCH}, author={Jones, Eric A. L. and Andres, Ryan J. and Owen, Micheal D. K. and Dunne, Jeffrey C. and Contreras, Diego J. and Cahoon, Charles W. and Jennings, Katherine M. and Leon, Ramon G. and Everman, Wesley J.}, year={2023}, month={Jul} }
 @article{thum_sperry_chorak_leon_ferrell_2023, title={Confusion and ambiguity concerning the terms "resistance" and "tolerance" in aquatic plant management}, volume={5}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2023.28}, DOI={10.1017/wsc.2023.28}, abstractNote={© The Author(s), 2023. Published by Cambridge University Press on behalf of the Weed Science Society of America. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http:// creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited. Confusion and ambiguity concerning the terms “resistance” and “tolerance” in aquatic plant management}, journal={WEED SCIENCE}, author={Thum, Ryan A. and Sperry, Benjamin P. and Chorak, Gregory M. and Leon, Ramon G. and Ferrell, Jason}, year={2023}, month={May} }
 @article{weisberger_leon_gruner_levi_gaur_morgan_basinger_2023, title={Demographics of Palmer amaranth (<i>Amaranthus palmeri</i>) in annual and perennial cover crops}, volume={11}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2023.66}, DOI={10.1017/wsc.2023.66}, abstractNote={AbstractPalmer amaranth (Amaranthus palmeri S. Watson) is the most problematic weed of cotton (Gossypium hirsutum L.)-cropping systems in the U.S. Southeast. Heavy reliance on herbicides has selected for resistance to multiple herbicide mechanisms of action. Effective management of this weed may require the integration of cultural practices that limit germination, establishment, and growth. Cover crops have been promoted as a cultural practice that targets these processes. We conducted a 2-yr study in Georgia, USA, to measure the effects of two annual cover crops (cereal rye [Secale cereale L.] and crimson clover [Trifolium incarnatum L.]), a perennial living mulch (‘Durana®’ white clover [Trifolium repens L.]), and a bare ground control on A. palmeri population dynamics. The study was conducted in the absence of herbicides. Growth stages were integrated into a basic demographic model to evaluate differences in population trajectories. Cereal rye and living mulch treatments suppressed weed seedling recruitment (seedlings seed−1) 19.2 and 13 times and 12 and 25 times more than the bare ground control, respectively. Low recruitment was correlated positively with low light transmission (photosynthetic active radiation: above canopy photosynthetically active radiation [PAR]/below cover crop PAR) at the soil surface. Low recruitment rates were also negatively correlated with high survival rates. Greater survival rates and reduced adult plant densities resulted in greater biomass (g plant−1) and fecundity (seeds plant−1) in cereal rye and living mulch treatments in both years. The annual rate of population change (seeds seed−1) was equivalent across all treatments in the first year but was greater in the living mulch treatment in the second year. Our results highlight the potential of annual cover crops and living mulches for suppressing A. palmeri seedling recruitment and would be valuable tools as part of an integrated weed management strategy.}, journal={WEED SCIENCE}, author={Weisberger, David A. and Leon, Ramon G. and Gruner, Chandler E. and Levi, Matthew and Gaur, Nandita and Morgan, Gaylon and Basinger, Nicholas T.}, year={2023}, month={Nov} }
 @article{jones_austin_dunne_leon_everman_2023, title={Discrimination between protoporphyrinogen oxidase-inhibiting herbicide-resistant and herbicide-susceptible redroot pigweed (Amaranthus retroflexus) with spectral reflectance}, volume={5}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2023.25}, DOI={10.1017/wsc.2023.25}, abstractNote={AbstractThe current assays to confirm herbicide resistance can be time- and labor-intensive (dose–response) or require a skill set/technical equipment (genetic sequencing). Stakeholders could benefit from a rapid assay to confirm herbicide-resistant weeds to ensure sustainable crop production. Because protoporphyrinogen oxidase (PPO)-inhibiting herbicides rapidly interfere with chlorophyll production/integrity; we propose a new, rapid assay utilizing spectral reflectance to confirm resistance. Leaf disks were excised from two PPO-inhibiting herbicide-resistant (target-site [TSR] and non–target site [NTSR]) and herbicide-susceptible redroot pigweed (Amaranthus retroflexus L.) populations and placed into a 24-well plate containing different concentrations (0 to 10 mM) of fomesafen for 48 h. A multispectral sensor captured images from the red (668 nm), green (560 nm), blue (475 nm), and red edge (717 nm) wavebands after a 48-h incubation period. The green leaf index (GLI) was utilized to determine spectral reflectance ratios of the treated leaf disks. Clear differences of spectral reflectance were observed in the red edge waveband for all populations treated with the 10 mM concentration in the dose–response assays. Differences of spectral reflectance were observed for the NTSR population compared with the TSR and susceptible populations treated with the 10 mM concentration in the green waveband and the GLI in the dose–response assay. Leaf disks from the aforementioned A. retroflexus populations and two additional susceptible populations were subjected to a similar assay with the discriminating concentration (10 mM). Spectral reflectance was different between the PPO-inhibiting herbicide-resistant and herbicide-susceptible populations in the red, blue, and green wavebands. Spectral reflectance was not distinctive between the populations in the red edge waveband and the GLI. The results provide a basis for rapidly (∼48 h) detecting PPO-inhibiting herbicide-resistant A. retroflexus via spectral reflectance. Discrimination between TSR and NTSR populations was possible only in the dose–response assay, but the assay still has utility in distinguishing herbicide-resistant plants from herbicide-susceptible plants.}, journal={WEED SCIENCE}, author={Jones, Eric A. L. and Austin, Robert and Dunne, Jeffrey C. and Leon, Ramon G. and Everman, Wesley J.}, year={2023}, month={May} }
 @article{iboyi_mulvaney_leon_balkcom_bashyal_devkota_small_2023, title={Double-cropping effects of Brassica carinata and summer crops: I. Effects of summer cropping history on carinata production}, volume={194}, ISSN={["1872-633X"]}, DOI={10.1016/j.indcrop.2023.116364}, abstractNote={Row croppers in the Southeast United States (SE US) are interested in diversifying their cropping systems and increasing revenue by growing a winter cash crop between summer crops, especially cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.). Double-cropping carinata (Brassica carinata A. Braun) between summer crops has potential to boost grower revenue and increase land use efficiency in the region. Given that this winter crop is fairly new in the SE US, its successful establishment in the region depends on its rotational fit into current cropping systems. Since incorporating carinata into the existing cropping systems in the region could influence the productivity of those systems, it is crucial to determine what changes row croppers should expect. To resolve this, research was conducted to quantify the effects of summer cropping history on the performance of carinata as part of diversified crop rotations in the SE US. A randomized complete block design with eight replications was implemented in Jay, Florida, over three years. Summer cropping history treatments were peanut, cotton, and summer fallow. Data was collected on carinata aboveground biomass and stover [including carbon (C) and nitrogen (N)]; yield (including yield components); and seed chemical composition (glucosinolates concentration, protein and oil contents, and oil composition). Carinata biomass, biomass C and N, stover residue, stover residue C and N, and stover residue C:N ratio were not affected by summer cropping history across years. Likewise, yield and seed chemical composition were not affected by summer cropping history. In terms of combined productivity of summer crops and carinata, cotton-carinata was the most productive system while fallow-carinata was the least productive. Overall, results from this study show that the insensitivity of carinata yield or seed quality to previous summer crops allows for flexibility in integrating carinata into existing rotations in the SE US. This simplifies the agronomic management of carinata as a biofuel crop since growers can concentrate on meeting yield goals without the risk of affecting yield or seed quality with different summer cropping histories.}, journal={INDUSTRIAL CROPS AND PRODUCTS}, author={Iboyi, Joseph E. and Mulvaney, Michael J. and Leon, Ramon G. and Balkcom, Kipling S. and Bashyal, Mahesh and Devkota, Pratap and Small, Ian M.}, year={2023}, month={Apr} }
 @article{iboyi_mulvaney_leon_devkota_bashyal_balkcom_small_2023, title={Double-cropping effects of Brassica carinata and summer crops: II. Effects of winter cropping history on subsequent summer crop production}, volume={197}, ISSN={["1872-633X"]}, DOI={10.1016/j.indcrop.2023.116609}, abstractNote={There is an opportunity for crop farmers in the Southeast United States (SE US) to increase income by producing carinata during the winter following summer crop production. However, a major limitation to the use of carinata as a winter annual in the SE US is the lack of information on double-cropping with summer commodity crops common to the region. Considering that integrating carinata into cropping systems common to the region could impact productivity of those systems, it is critical to quantify the potential effects of carinata on existing cropping systems. To this end, a study was conducted in Jay, Florida for three years to evaluate the effects of winter cropping history (carinata vs. fallow) on the productivity of subsequent summer crops including cotton, peanut, sorghum, and soybean. Treatments (winter carinata vs. winter fallow) were laid out in a randomized complete block design with eight replications. Data were collected on infiltration; plant population; plant canopy height; aboveground biomass; and yield. Infiltration rates, determined within a week of carinata harvest, were affected by winter cropping history, being greater in former carinata plots than former fallow plots. Carinata harvest coincided with the timely planting of cotton and peanut which resulted in these summer crops being sown three to four weeks later than their typical sowing window for the SE US. Winter cropping history (including the winter fallow control) did not influence commodity crop (cotton, peanut, sorghum, and soybean) yields when all summer crops were planted at the same time, as in a double-crop scenario. Regarding the combined productivity of winter (carinata vs. winter fallow) and summer crops, carinata-cotton, carinata-peanut, carinata-sorghum, and carinata-soybean systems were necessarily more productive than their winter fallow counterparts due to no crop production in the fallow during the winter cropping years. Overall, results from this study showed that carinata can successfully replace winter fallow, and can be double-cropped with summer-planted sorghum and soybean with no adverse effect on yield. Double-cropping carinata caused a delay in timely planting of cotton and peanut, and represents a limitation that may hinder its adoption in the SE US until such time a faster-maturing carinata cultivar can be developed.}, journal={INDUSTRIAL CROPS AND PRODUCTS}, author={Iboyi, Joseph E. and Mulvaney, Michael J. and Leon, Ramon G. and Devkota, Pratap and Bashyal, Mahesh and Balkcom, Kipling S. and Small, Ian M.}, year={2023}, month={Jul} }
 @article{moore_jennings_monks_boyette_leon_jordan_ippolito_blankenship_chang_2023, title={Evaluation of electrical and mechanical Palmer amaranth (Amaranthus palmeri) management in cucumber, peanut, and sweetpotato}, volume={1}, ISSN={["1550-2740"]}, url={https://doi.org/10.1017/wet.2023.1}, DOI={10.1017/wet.2023.1}, abstractNote={AbstractField studies were conducted to assess the efficacy of physical weed management of Palmer amaranth management in cucumber, peanut, and sweetpotato. Treatments were arranged in a 3 × 4 factorial in which the first factor included a treatment method of electrical, mechanical, or hand-roguing Palmer amaranth control and the second factor consisted of treatments applied when Palmer amaranth was approximately 0.3, 0.6, 0.9, or 1.2 m above the crop canopy. Four wk after treatment (WAT), the electrical applications controlled Palmer amaranth at least 27 percentage points more than the mechanical applications when applied at the 0.3- and 0.6-m timings. At the 0.9- and 1.2-m application timings 4 WAT, electrical and mechanical applications controlled Palmer amaranth by at most 87%. Though hand removal generally resulted in the greatest peanut pod count and total sweetpotato yield, mechanical and electrical control resulted in similar yield to the hand-rogued plots, depending on the treatment timing. With additional research to provide insight into the optimal applications, there is potential for electrical control and mechanical control to be used as alternatives to hand removal. Additional studies were conducted to determine the effects of electrical treatments on Palmer amaranth seed production and viability. Treatments consisted of electricity applied to Palmer amaranth at first visible inflorescence, 2 wk after first visible inflorescence (WAI) or 4 WAI. Treatments at varying reproductive maturities did not reduce the seed production immediately after treatment. However, after treatment, plants primarily died and ceased maturation, reducing seed production assessed at 4 WAI by 93% and 70% when treated at 0 and 2 WAI, respectively. Treatments did not have a negative effect on germination or seedling length.}, journal={WEED TECHNOLOGY}, author={Moore, Levi D. D. and Jennings, Katherine M. M. and Monks, David W. W. and Boyette, Michael D. D. and Leon, Ramon G. G. and Jordan, David L. L. and Ippolito, Stephen J. J. and Blankenship, Colton D. D. and Chang, Patrick}, year={2023}, month={Jan} }
 @article{mahoney_jordan_leon_oreja_roma-burgos_2023, title={Fecundity and maternal effects on Palmer amaranth height following season-long interference in corn, cotton, and peanut}, volume={9}, ISSN={["2374-3832"]}, url={https://doi.org/10.1002/cft2.20233}, DOI={10.1002/cft2.20233}, abstractNote={AbstractPalmer amaranth (Amaranthus palmeri Watson) is one of the most difficult‐to‐control weeds in several economically important crops in the United States. Growth characteristics of Palmer amaranth can be affected by the cropping system. Research was conducted in North Carolina in 2019 to determine height and seed production of Palmer amaranth grown season long in the presence of corn (Zea mays L.), cotton (Gossypium hirsutum L.), and peanut (Arachis hypogaea L.). Research was also conducted to determine transgenerational effects due to interference from these crops. Palmer amaranth produced more seed when grown with cotton (17 times greater) and peanut (12 times greater) compared with corn; no difference was noted between cotton and peanut. Palmer amaranth height in the field at physiological maturity was similar in corn (80 inches) and cotton (77 inches) and taller in height than peanut (63 inches). When progeny from plants in the field were grown in the greenhouse in the absence of crop interference, differences in the height of progeny and height of the mother plant in the presence of crop interference were ranked similarly with respect to crop. Palmer amaranth height in the presence of corn and cotton was similar (57 and 58 inches, respectively) and it exceeded height when the weed was grown with peanut (51 inches). These results demonstrate transgenerational effects due to previous crop (e.g., corn, cotton, and peanut) for Palmer amaranth.}, number={2}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, author={Mahoney, Denis J. and Jordan, David L. and Leon, Ramon and Oreja, Fernando H. and Roma-Burgos, Nilda}, year={2023}, month={Dec} }
 @article{sousa-ortega_leon_lopez-martinez_castro-valdecantos_2023, title={Influence of burial depth and soil disturbance on the emergence of common weed species in the Iberian Peninsula}, volume={5}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2023.30}, DOI={10.1017/wsc.2023.30}, abstractNote={AbstractNorth African knapweed (Centaurea diluta Aiton), cornflower (Centaurea cyanus L.), corn marigold [Glebionis segetum (L.) Fourr.], rigid ryegrass (Lolium rigidum Gaudin), and corn poppy (Papaver rhoeas L.) are weeds of economic importance in the Iberian Peninsula, particularly due to limited herbicide options for effective control. For this reason, information about their seedling emergence has become critical to develop effective integrated management strategies and better time control actions. The aims of this study were to evaluate the effect of seed burial depth and soil disturbance on the emergence of these weed species. Two pot experiments were carried out to (1) quantify seedling emergence at three burial depths (2, 5, and 9 cm) and (2) characterize seedling emergence in response to different frequencies and timings of soil disturbance. Burial depth limited the emergence of G. segetum and P. rhoeas at 5 and 9 cm, respectively; while seedling emergence of C. diluta, C. cyanus, and L. rigidum were reduced by 92%, 90%, and 67% at 9 cm compared with 2 cm, respectively. Two or more sequential soil disturbance events increased total seedling emergence of C. diluta, P. rhoeas, and G. segetum compared with single events, while L. rigidum did not respond to repeated soil disturbance. These results suggest that turning the soil to bury weed seeds down to 5 cm or deeper would be a very effective method to control G. segetum and P. rhoeas and moderately effective to control C. cyanus. Also, the use of a stale seedbed would have some efficacy to reduce P. rhoeas and C. diluta weed pressure within the crop. This study illustrates how differences among species in seedling emergence in response to soil depth and disturbance can determine distinct emergence patterns ultimately influencing the selection of weed control tools and timing.}, journal={WEED SCIENCE}, author={Sousa-Ortega, Carlos and Leon, Ramon G. and Lopez-Martinez, Nuria and Castro-Valdecantos, Pedro}, year={2023}, month={May} }
 @article{howell_haug_everman_leon_richardson_2023, title={Low carrier volume herbicide trials and UAAS support management efforts of giant salvinia (Salvinia molesta): a case study}, volume={5}, ISSN={["1939-747X"]}, url={https://doi.org/10.1017/inp.2023.16}, DOI={10.1017/inp.2023.16}, abstractNote={AbstractExpanding the current aquatic herbicide portfolio, reducing total spray volumes, or remotely delivering herbicide using novel spray technologies could improve management opportunities targeting invasive aquatic plants, where options are more limited. However, research on giant salvinia (Salvinia molesta Mitchell) response to foliar herbicide applications at carrier volumes ≤140 L ha−1 is incomplete. Likewise, no data exist documenting S. molesta control with unoccupied aerial application systems (UAAS). Following the recent >100-ha incursion of S. molesta in Gapway Swamp, NC, a case study was developed to provide guidance for ongoing management efforts. In total, three field trials evaluated registered aquatic and experimental herbicides using a 140 L ha−1 carrier volume. Select foliar applications from UAAS were also evaluated. Results at 8 wk after treatment (WAT) indicated the experimental protoporphyrinogen oxidase inhibitor, PPO-699-01 (424 g ai ha−1), in combination with endothall dipotassium salt (2,370 g ae ha−1) provided 78% visual control, whereas control when PPO-699-01 (212 g ai ha−1) was applied alone was lower at 35%. Evaluations also showed diquat (3,136 g ai ha−1) alone, glyphosate (4,539 g ae ha−1) alone, and metsulfuron-methyl (42 g ai ha−1) alone achieved 86% to 94% visual plant control at 8 WAT. Sequential foliar applications of diquat, flumioxazin (210 g ai ha−1), and carfentrazone (67 g ai ha−1) at 6 wk following exposure to in-water fluridone treatments were no longer efficacious by 6 WAT due to plant regrowth. Carfentrazone applications made from a backpack sprayer displayed greater control than applications made with UAAS deploying identical carrier volumes at 2 WAT; however, neither application method provided effective control at 8 WAT. Additional field validation is needed to further guide management direction of S. molesta control using low carrier volume foliar applications.}, journal={INVASIVE PLANT SCIENCE AND MANAGEMENT}, author={Howell, Andrew W. and Haug, Erika J. and Everman, Wesley J. and Leon, Ramon G. and Richardson, Robert J.}, year={2023}, month={May} }
 @article{leon_bassham_2023, title={PROTAC for agriculture: learning from human medicine to generate new biotechnological weed control solutions}, volume={9}, ISSN={["1526-4998"]}, url={https://doi.org/10.1002/ps.7741}, DOI={10.1002/ps.7741}, abstractNote={AbstractWeed control has relied on the use of organic and inorganic molecules that interfere with druggable targets, especially enzymes, for almost a century. This approach, although effective, has resulted in multiple cases of herbicide resistance. Furthermore, the rate of discovery of new druggable targets that are selective and with favorable environmental profiles has slowed down, highlighting the need for innovative control tools. The arrival of the biotechnology and genomics era gave hope to many that all sorts of new control tools would be developed. However, the reality is that most efforts have been limited to the development of transgenic crops with resistance to a few existing herbicides, which in fact is just another form of selectivity. Proteolysis‐targeting chimera (PROTAC) is a new technology developed to treat human diseases but that has potential for multiple applications in agriculture. This technology uses a small bait molecule linked to an E3 ligand. The 3‐dimensional structure of the bait favors physical interaction with a binding site in the target protein in a manner that allows E3 recruitment, ubiquitination and then proteasome‐mediated degradation. This system makes it possible to circumvent the need to find druggable targets because it can degrade structural proteins, transporters, transcription factors, and enzymes without the need to interact with the active site. PROTAC can help control herbicide‐resistant weeds as well as expand the number of biochemical targets that can be used for weed control. In the present article, we provide an overview of how PROTAC works and describe the possible applications for weed control as well as the challenges that this technology might face during development and implementation for field uses. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.}, journal={PEST MANAGEMENT SCIENCE}, author={Leon, Ramon G. and Bassham, Diane C.}, year={2023}, month={Sep} }
 @article{howell_leon_everman_mitasova_nelson_richardson_2023, title={Performance of unoccupied aerial application systems for aquatic weed management: Two novel case studies}, volume={37}, ISSN={0890-037X 1550-2740}, url={http://dx.doi.org/10.1017/wet.2023.32}, DOI={10.1017/wet.2023.32}, abstractNote={AbstractUnoccupied aerial application systems (UAAS) are gaining popularity for weed management to increase applicator safety and to deliver herbicide treatments where treatment sites limit ground-based spray equipment. Several studies have documented UAAS application strategies and procedures for weed control in terrestrial settings, yet literature describing remote spray technology for use in aquatics remains limited. Currently, applicators seek guidance for UAAS deployment for aquatic weed management to overcome site access restrictions, deal with environmental limitations, and improve ground-based applicator safety in hazardous treatment scenarios. In the present case studies, we evaluate a consumer-available UAAS to deliver the herbicide, florpyrauxifen-benzyl, as both foliar and directed in-water spray applications. The first case study showed that the invasive floating-leaved plant, yellow floating heart, was controlled 80% to 99% by 6 wk after treatment (WAT) following UAAS foliar herbicide treatments. The second case study demonstrated that UAAS directed in-water herbicide application reduced variable-leaf watermilfoil visible plant material by 94% at 5 WAT. Likewise, directed in-water applications from UAAS eliminated the need to deploy watercraft, which improved overall operational efficiency. Data from both case studies indicate that UAAS can provide an effective and efficient treatment strategy for floating-leaved and submersed plant control among common herbicide treatment scenarios. Future integration of UAAS in aquatic weed control programs is encouraged, especially among smaller treatment sites (≤4 ha) or where access limits traditional spray operations.}, number={3}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Howell, Andrew W. and Leon, Ramon G. and Everman, Wesley J. and Mitasova, Helena and Nelson, Stacy A.C. and Richardson, Robert J.}, year={2023}, month={May}, pages={277–286} }
 @article{oreja_hare_jordan_leon_2023, title={Previous crop and herbicide timing application effects on weed population growth rate}, volume={9}, ISSN={["2374-3832"]}, url={https://doi.org/10.1002/cft2.20232}, DOI={10.1002/cft2.20232}, abstractNote={AbstractA well‐designed crop rotation can create an unstable environment that disrupts weed population growth rates. In combination with effective herbicide programs, growers may maintain weed populations at levels below competitive and economic thresholds. The objectives of the present study were to evaluate how the preceding rotational crop determines the response of weed populations to in‐season postemergence herbicide programs and the weed population density of the following crop season. The first‐year crop treatments were corn (Zea mays L.), cotton (Gossypium hirsutum L.), peanut (Arachis hypogaea L.), grain sorghum [Sorghum bicolor (L.) Moench.], and soybean [Glycine max (L.) Merr.]. In the second year, all plots were planted with cotton, and herbicide treatments were single applications 2 or 6 weeks after planting (WAP), two sequential applications 2 and 4 or 4 and 6 WAP, three sequential applications 2, 4, and 6 WAP, and a weedy control without herbicides was included. In the absence of herbicides, corn had the lowest population growth rates for broadleaf weeds (λ = 0.8) while peanut and grain sorghum had the highest (λ = 1.7 and 1.3, respectively). The results indicated that herbicide applications focused exclusively on preventing yield loss may not be sufficient to ensure weed population reductions. Thus, the observed population growth rates (λ = 2 for grassy weeds and λ = 1.26 for broadleaved weeds) indicated that weed issues would continue increasing, despite meeting yield goals. Considering population growth rates when assessing weed management strategies is key to determining the sustainability of the crop production operation.}, number={2}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, author={Oreja, Fernando H. and Hare, Andrew T. and Jordan, David L. and Leon, Ramon G.}, year={2023}, month={Dec} }
 @article{ethridge_chandra_everman_jordan_locke_owen_leon_2023, title={Rapid evolution of competitive ability in giant foxtail (<i>Setaria faberi</i>) over 34 years}, volume={71}, ISSN={0043-1745 1550-2759}, url={http://dx.doi.org/10.1017/wsc.2023.1}, DOI={10.1017/wsc.2023.1}, abstractNote={AbstractCompetition between genotypes within a plant population can result in the displacement of the least competitive by more competitive genotypes. Although evolutionary processes in plants may occur over thousands and millions of years, it has been suggested that changes in key fitness traits could occur in as little as decades, with herbicide resistance being a common example. However, the rapid evolution of complex traits has not been proven in weeds. We hypothesized that changes in weed growth and competitive ability can occur in just a few years because of selection in agroecosystems. Seed of multiple generations of a single natural population of the grassy weed giant foxtail (Setaria faberi Herrm.) were collected during 34 yr (i.e., 1983 to 2017). Using a “resurrection” approach, we characterized life-history traits of the different year-lines under noncompetitive and competitive conditions. Replacement-series experiments comparing the growth of the oldest year-line (1983) versus newer year-lines (1991, 1996, 1998, 2009, and 2017) showed that plant competitive ability decreased and then increased progressively in accordance with oscillating selection. The adaptations in competitive ability were reflected in dynamic changes in leaf area and biomass when plants were in competition. The onset of increased competitive ability coincided with the introduction of herbicide-resistant crops in the landscape in 1996. We also conducted a genome-wide association study and identified four loci that were associated with increased competitive ability over time, confirming that this trait changed in response to directional selection. Putative transcription factors and cell wall–associated enzymes were linked to those loci. This is the first study providing direct in situ evidence of rapid directional evolution of competitive ability in a plant species. The results suggest that agricultural systems can exert enough pressure to cause evolutionary adaptations of complex life-history traits, potentially increasing weediness and invasiveness.}, number={1}, journal={Weed Science}, publisher={Cambridge University Press (CUP)}, author={Ethridge, Sandra R. and Chandra, Saket and Everman, Wesley J. and Jordan, David L. and Locke, Anna M. and Owen, Micheal D. K. and Leon, Ramon G.}, year={2023}, month={Jan}, pages={59–68} }
 @article{camacho_faundez-urbina_amoozegar_gannon_heitman_leon_2023, title={Subsurface Lateral Solute Transport in Turfgrass}, volume={13}, ISSN={["2073-4395"]}, url={https://doi.org/10.3390/agronomy13030903}, DOI={10.3390/agronomy13030903}, abstractNote={Turfgrass managers have suspected that runoff-independent movement of herbicides and fertilizers is partially responsible for uneven turfgrass quality in sloped areas. We hypothesized that subsurface lateral solute transport might explain this phenomenon especially in areas with abrupt textural changes between surface and subsurface horizons. A study was conducted to track solute transport using bromide (Br−), a conservative tracer, as a proxy of turfgrass soil inputs. Field data confirmed the subsurface lateral movement of Br− following the soil slope direction, which advanced along the boundary between soil horizons over time. A model based on field data indicated that subsurface lateral movement is a mechanism that can transport fertilizers and herbicides away from the application area after they have been incorporated within the soil, and those solutes could accumulate and resurface downslope. Our results demonstrate that subsurface lateral transport of solutes, commonly ignored in risk assessment, can be an important process for off-target movement of fertilizers and pesticides within soils and turfgrass systems in sloped urban and recreational landscapes.}, number={3}, journal={AGRONOMY-BASEL}, author={Camacho, Manuel E. and Faundez-Urbina, Carlos A. and Amoozegar, Aziz and Gannon, Travis W. and Heitman, Joshua L. and Leon, Ramon G.}, year={2023}, month={Mar} }
 @article{bashyal_mulvaney_devkota_wilson_iboyi_leon_landry_boote_2023, title={Summer crop rotational effects on carinata nitrogen management in the southeastern USA}, volume={6}, ISSN={["1435-0645"]}, url={https://doi.org/10.1002/agj2.21373}, DOI={10.1002/agj2.21373}, abstractNote={AbstractGrowers in the United States (US) southeast are often recommended to reduce nitrogen (N) fertilization after peanut (Arachis hypogaea L.) by cooperative Extension services. However, these guidelines are not supported by the scientific literature. An experiment was conducted to quantify N contributions from peanut residues to a subsequent carinata (Brassica carinata) crop. A 3 (history: cotton [Gossypium hirsutum L.], peanut, fallow) × 5 (N rates: 0, 34, 67, 101,134 kg N ha−1) factorial randomized complete block split‐plot design was conducted over four site‐years during the 2018–2019 and 2019–2020 seasons at Jay, FL, USA. Peanut and cotton were planted under strip tillage, whereas carinata was drilled into peanut and cotton residues and weed‐free fallow plots. Although peanut residues accumulated 54–78 kg N ha−1, inorganic N content behind former peanut plots at the 0–15 cm depths, ranged from 6 to 8 and 8 to 11 kg N ha−1 in 2018–2019 and 2019–2020 season, respectively. Cropping history differences for carinata normalized difference vegetation index (NDVI) were pronounced at lower N rates in one out of four site‐years during which NDVI behind former cotton plots was lower than former peanut and fallow plots. Carinata seed yield behind former peanut plots was similar to unfertilized fallow based on four site‐years of data. Nonlinear regression models predicted that N rates required to optimize carinata seed yield following peanut would exceed 134 kg N ha−1 thereby indicating negligible peanut N credits. These results support a growing body of literature that suggests minimal N credits after peanut under humid southeastern US conditions.}, journal={AGRONOMY JOURNAL}, author={Bashyal, Mahesh and Mulvaney, Michael J. and Devkota, Pratap and Wilson, Chris and Iboyi, Joseph E. and Leon, Ramon G. and Landry, Gabriel M. and Boote, Kenneth J.}, year={2023}, month={Jun} }
 @article{sousa-ortega_alcantara_leon_barranco-elena_saavedra_2023, title={The impact of burial depth on <i>Centaurea dilut</i>a emergence and modelling of its growth using a nonlinear regression and artificial neural network}, volume={11}, ISSN={["1526-4998"]}, url={https://doi.org/10.1002/ps.7848}, DOI={10.1002/ps.7848}, abstractNote={AbstractBACKGROUNDCentaurea diluta Aiton (North African knapweed) is a major weed concern in Spain as a result of the limited herbicides capable of controlling it, and the limited knowledge of its biology hinders the development of integrated weed management strategies.RESULTSThe current study presents results from two experiments that aimed to: (i) determine the effect of seed burial on seedling emergence; and (ii) model its phenology progression using sigmoidal (SRM) and artificial neural network models (ANN) based on different cohort emergence times. In the first experiment, burial at 2 cm and 5 cm decreased C. diluta emergence by 54% and 90%, respectively, compared to the emergence at 0 cm. In the second experiment, without crop–weed competition conditions, the emergence delay led to reductions in leaf number, rosette diameter, plant height and dry biomass by 63%, 50%, 59% and 93%, respectively. Seed production per plant exceeded 21 469. According to the growth model, leaf number was the most consistent morphological trait and critical for timing weed control actions, so it was used to compare SRMs and ANNs. On average, ANNs increased the precision in 5.72% (± 2.4 leaves) compared to SRMs. This slight performance of ANNs may be valuable for controlling C. diluta because control methods must be applied at the 4‐leaf stage to achieve good efficacy.CONCLUSIONSeed burial at 5 cm depth is an effective method reducing C. diluta emergence. ANNs accurately predicted the leaf number employing environmental variables can help increase the efficiency of C. diluta control actions and reduce the risk of escapes. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.}, journal={PEST MANAGEMENT SCIENCE}, author={Sousa-Ortega, Carlos and Alcantara, Cristina and Leon, Ramon G. and Barranco-Elena, Diego and Saavedra, Milagros}, year={2023}, month={Nov} }
 @article{dobbs_ginn_skovsen_yadav_jha_bagavathiannan_mirsky_reberg-horton_leon_2023, title={Using structure-from-motion to estimate cover crop biomass and characterize canopy structure}, volume={302}, ISSN={["1872-6852"]}, DOI={10.1016/j.fcr.2023.109099}, abstractNote={Variability in biomass production poses a challenge for growers when using cover crops for weed control. However, most methods for assessing cover crop biomass are laborious and impractical on a field scale. The goal of the present study was to determine the feasibility of using Structure-from-Motion (SfM) photogrammetry to estimate biomass in cereal rye (Secale cereale L.) and winter wheat (Triticum aestivum L.) cover crops by correlating biomass with 3-D point cloud pixel density and crop height. Point clouds were generated using a SfM algorithm from RGB (red, green, and blue) videos collected by a hand-held GoPro camera over sixteen crop fields in North Carolina, Iowa, and Maryland, USA, throughout two growing seasons (2021–2023). Crop height, leaf area index (LAI), and photosynthetically active radiation (PAR) were also measured. Biomass was positively correlated with crop height for both cereal rye (R2 = 0.621) and wheat (R2 = 0.55). LAI was positively correlated with biomass accumulation and crop height for both species, increasing linearly in rye and exponentially in wheat. Conversely, PAR penetration below the canopy decreased with biomass accumulation and crop height in both species, with a more rapid extinction in wheat than rye. Point cloud pixel density showed a positive linear relationship with biomass in rye but saturated after 2.5 tonnes ha−1 (2500 kg ha−1). In wheat, point cloud pixel density was weakly and negatively correlated with biomass due to a denser canopy causing faster saturation of tissue detection by SfM point clouds. However, considering crop height and point cloud density integrating them both in the model allowed obtaining a positive relationship with biomass through levels of 8 tonnes ha−1 (8000 kg ha−1) in both species. When models were validated with independent data, predicted and measured biomass were positively correlated for both rye (R2 = 0.86) and wheat (R2 = 0.78). Based on the results, using SfM to generate 3-D point clouds can provide a more accurate estimation of biomass than canopy height alone by capturing species-level differences in canopy architecture. The results of this study suggest that SfM can potentially be used as a non-destructive tool for growers to monitor biomass production in cereal cover crops other systems such as energy/forage crops, which can help inform management decisions and conserve resources.}, journal={FIELD CROPS RESEARCH}, author={Dobbs, April M. and Ginn, Daniel and Skovsen, Soren Kelstrup and Yadav, Ramawatar and Jha, Prashant and Bagavathiannan, Muthukumar V and Mirsky, Steven B. and Reberg-Horton, Chris S. and Leon, Ramon G.}, year={2023}, month={Oct} }
 @article{dobbs_sousa-ortega_holland_snyder_leon_2023, title={Variability structure and heritability of germination timing in <i>Capsella bursa-pastoris</i> (L.) Medik. (Shepherd&apos;s purse)}, volume={12}, ISSN={["1365-3180"]}, url={https://doi.org/10.1111/wre.12605}, DOI={10.1111/wre.12605}, abstractNote={AbstractGermination variability enables weedy species to colonise disturbed habitats and is expected to evolve in response to changing selection pressures. The paucity of information about germination variability in weeds prompted a detailed study of this topic with two agricultural and two non‐agricultural populations of Capsella bursa‐pastoris (Shepherd's purse). Variance in germination time was partitioned amongst and within populations, and amongst racemes and silicles within individual plant, and broad‐sense heritability (H2) was estimated. Agricultural populations exhibited a shorter and more uniform germination timing than non‐agricultural populations. However, differences amongst populations explained 7%–12% of the total variance, while differences amongst individuals and racemes accounted for approximately 40–54% and 10% of the total variance for germination time. For germination time, H2 = 0.4 when averaged across all time points, peaking at H2 = 0.7 at a time coinciding with the exponential phase of the germination curve. Maintaining predominantly intrapopulation variability in germination timing appears to be important for long‐term fitness in this species.}, journal={WEED RESEARCH}, author={Dobbs, April M. and Sousa-Ortega, Carlos and Holland, James B. and Snyder, Lori Unruh and Leon, Ramon G.}, year={2023}, month={Dec} }
 @article{ethridge_grieger_locke_everman_jordan_leon_2023, title={Views of RNAi approaches for weed management in turfgrass systems}, volume={7}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2023.37}, DOI={10.1017/wsc.2023.37}, abstractNote={AbstractPublic concern regarding the use of herbicides in urban areas (e.g., golf courses, parks, lawns) is increasing. Thus, there is a need for alternative methods for weed control that are safe for the public, effective against weeds, and yet selective to turfgrass and other desirable species. New molecular tools such as ribonucleic acid interference (RNAi) have the potential to meet all those requirements, but before these technologies can be implemented, it is critical to understand the perceptions of key stakeholders to facilitate adoption as well as regulatory processes. With this in mind, turfgrass system managers, such as golf course superintendents and lawn care providers, were surveyed to gain insight into the perception and potential adoption of RNAi technology for weed management. Based on survey results, turfgrass managers believe that cost of weed management and time spent managing weeds are the main challenges faced in their fields. When considering new weed management tools, survey respondents were most concerned about cost, efficacy, and efficiency of a new product. Survey respondents were also optimistic toward RNAi for weed management and would either use this technology in their own fields or be willing to conduct research to develop RNAi herbicides. Although respondents believed that the general public would have some concerns about this technology, they did not believe this to be the most important factor for them when choosing new weed management tools. The need for new herbicides to balance weed control challenges and public demands is a central factor for turfgrass managers’ willingness to use RNAi-based weed control in turfgrass systems. They believe their clientele will be accepting of RNAi tools, although further research is needed to investigate how a wider range of stakeholders perceive RNAi tools for turfgrass management more broadly.}, journal={WEED SCIENCE}, author={Ethridge, Sandra R. and Grieger, Khara and Locke, Anna M. and Everman, Wesley J. and Jordan, David L. and Leon, Ramon G.}, year={2023}, month={Jul} }
 @article{dobbs_reberg-horton_snyder_leon_2022, title={Assessing weediness potential of Brassica carinata (A.) Braun in the southeastern United States}, volume={188}, ISSN={["1872-633X"]}, DOI={10.1016/j.indcrop.2022.115611}, abstractNote={Carinata (Brassica carinata (A.) Braun) is a promising winter oilseed crop in the southeastern US, and ensuring agricultural and ecological safety is critical for growers. The present study evaluated the weediness and invasiveness potential for carinata in the southeastern US. A field study was conducted in Goldsboro and Clayton, North Carolina comparing emergence and survival of volunteer carinata with and without predator exclusion. Cumulative seedling emergence at both locations was highest for buried seeds with predator exclusion (42% and 15%) and lowest in unburied seeds without predator exclusion (16% and 1%). Survival 90 days after planting (DAP) at both locations was highest for buried seeds with predator exclusion (10% and 5%) and lowest in unburied seeds without predator exclusion (3% and <1%). Frost damage contributed to predator damage increasing mortality of established plants to 100% 120 DAP. In addition to the field study, the Australian Weed Risk Assessment (WRA) and Plant Risk Evaluation were conducted for carinata. The cumulative score for the Australian WRA was –1 (low risk), which was below the minimum score of 6 for rejection of introduction. The agricultural and environmental scores were –5 and –2, corresponding to a low risk in agricultural and non-agricultural settings. The cumulative Plant Risk Evaluation score was 6 (low risk), which was below the minimum score of 13 for rejection. Based on the field study and risk assessments, it was concluded that there is low risk of weediness and invasiveness for volunteer carinata in the southeastern US.}, journal={INDUSTRIAL CROPS AND PRODUCTS}, author={Dobbs, April M. and Reberg-Horton, S. Chris and Snyder, Lori Unruh and Leon, Ramon G.}, year={2022}, month={Nov} }
 @article{jones_leon_everman_2022, title={Biological effects on Palmer amaranth surviving glufosinate}, volume={5}, ISSN={["2639-6696"]}, url={https://doi.org/10.1002/agg2.20315}, DOI={10.1002/agg2.20315}, abstractNote={AbstractPalmer amaranth (Amaranthus palmeri S. Watson) is a difficult weed to manage due to competitive growth, fecundity, and evolved herbicide resistance. Limited information exist on the fecundity of vegetative stage Palmer amaranth surviving glufosinate applied at different timings. In addition, research has not investigated the germination or glufosinate susceptibility of the offspring from these surviving plants. Field experiments were conducted across three locations in 2019 to determine (a) the fecundity of Palmer amaranth plants surviving glufosinate applied at different vegetative growth stages, and (b) if the offspring from the surviving plants exhibited differential germination and susceptibility to glufosinate. Palmer amaranth was treated at three different vegetative sizes (5 cm, 7–10 cm, > 10 cm) and orthogonal combinations of these application timings. The application timings corresponded to early‐, mid‐ and late‐postemergence applications. Palmer amaranth plants surviving the mid‐, late‐, and the mid postemergence followed by late postemergence glufosinate application were fecund. Palmer amaranth plants surviving the mid postemergence followed by late postemergence application produced less seed than the plants surviving the mid postemergence and late postemergence application. Palmer amaranth was controlled with other glufosinate applications resulting in no seed production. Germination was affected across location and glufosinate treatments, but no clear trend/pattern was observed. The offspring from Palmer amaranth plants surviving glufosinate applications were controlled by all glufosinate rates tested. These experiments provide evidence that Palmer amaranth surviving glufosinate in the vegetative stages may remain fecund, but fecundity can vary with application timing. No measurable effect on the offspring germination or susceptibility to glufosinate was apparent.}, number={4}, journal={AGROSYSTEMS GEOSCIENCES & ENVIRONMENT}, author={Jones, Eric and Leon, Ramon G. and Everman, Wesley Jay}, year={2022} }
 @article{bashyal_mulvaney_crozier_iboyi_perondi_post_iskandar_leon_landry_wilson_et al._2023, title={Brassica carinata nutrient accumulation and partitioning across maturity types and latitude}, volume={2}, ISSN={["1435-0653"]}, url={https://doi.org/10.1002/csc2.20900}, DOI={10.1002/csc2.20900}, abstractNote={AbstractAs a recently introduced crop in the United States, there are limited data regarding temporal nutrient accumulation and partitioning dynamics of Brassica carinata (carinata). A four site‐year study was conducted in Jay, FL and Salisbury, NC during the 2018–2019 and 2019–2020 growing seasons. Three carinata genotypes (DH‐157.715, M‐01, and Avanza 641) proposed by the industry to represent early‐, mid‐, and full‐season genotypes, respectively, were sampled at multiple growth stages and partitioned into leaves, stems, reproductive parts (flowers plus pods), and seed to determine biomass and nutrient accumulation across three genotypes in Florida and one full season genotype in North Carolina. Averaged over two site‐years and genotypes in Florida, accumulation (per ha) of 169 kg N, 22 kg P, 160 kg K, 58 kg S, 475 g Zn, and 218 g B was required to produce 1635 and 10,872 kg ha−1 of seed yield and biomass, respectively. Nutrients with high harvest index values included P (60%), N (55%), S (32%), and Mg (29%). Averaged over two site‐years in North Carolina, accumulation (per ha) of 178 kg N, 26 kg P, 87 kg K, 24 kg S, 416 g Zn, and 127 g B produced 2428 and 9102 kg ha−1 of seed yield and biomass, respectively. Nutrients with greatest harvest index values were P (57%), N (50%), S (32%), and Mg (26%). Internal efficiency of N, P, and K, measured as slopes of seed yield regressions over nutrient uptake across all genotypes and locations were 16, 83, and 8 kg seed yield per kg N, P, and K uptake, respectively. These results describe temporal nutrient accumulation and partitioning in carinata and are critical to refine nutrient management strategies and guide fertilizer application decisions.}, journal={CROP SCIENCE}, author={Bashyal, Mahesh and Mulvaney, Michael J. and Crozier, Carl R. and Iboyi, Joseph E. and Perondi, Daniel and Post, Angela and Iskandar, Keola and Leon, Ramon G. and Landry, Gabriel M. and Wilson, Chris and et al.}, year={2023}, month={Feb} }
 @article{jones_leon_everman_2022, title={Control of pervasive row crop weeds with dicamba and glufosinate applied alone, mixed, or sequentially}, volume={10}, ISSN={["1550-2740"]}, url={https://doi.org/10.1017/wet.2022.80}, DOI={10.1017/wet.2022.80}, abstractNote={AbstractDicamba and glufosinate are among the few effective postemergence herbicides to control multiple herbicide-resistant weeds in southeastern U.S. cotton and soybean production. Field studies were conducted to determine the effect of weed size and the application of dicamba and glufosinate individually, mixed, or sequentially on common ragweed, goosegrass, large crabgrass, ivyleaf morningglory, Palmer amaranth, and sicklepod control. Sequential herbicide treatments were applied 7 d after the initial treatment. The tested weeds sizes predominantly did not affect weed control. Control of broadleaf weed species with sequential herbicide applications never increased compared to the initial herbicide application. Two applications of glufosinate and/or dicamba + glufosinate controlled grasses better than one application. The order of the herbicides in the sequential applications did not affect broadleaf species control, whereas herbicide order was important for the control of grass weeds. Grass weed control was higher when glufosinate was applied before dicamba. Dicamba + glufosinate additively controlled the weeds, except for goosegrass, for which control was less for dicamba + glufosinate compared to glufosinate alone. The results of the experiment provide evidence that dicamba and glufosinate applied individually, mixed, and sequentially are effective on common row crop weeds found in the southeastern United States, but the species present may dictate how the herbicides are applied together.}, journal={WEED TECHNOLOGY}, author={Jones, Eric A. L. and Leon, Ramon G. and Everman, Wesley J.}, year={2022}, month={Oct} }
 @article{contreras_leon_post_everman_2022, title={Critical period of grass weed control in ALS-tolerant grain sorghum (Sorghum bicolor) is affected by planting date and environment}, volume={4}, ISSN={["2673-3218"]}, DOI={10.3389/fagro.2022.1014801}, abstractNote={Field experiments were conducted at two locations in North Carolina (Clayton and Rocky Mount) to determine the influence of row spacing and planting date on the critical period of weed control (CPWC) of grass weeds in ALS-tolerant grain. Grain sorghum was planted in May and June 2019, with either a 38 or 91 cm row spacing using an ALS-tolerant sorghum variety. Treatments consisted of “weedy” or “weed-free” plots up to 2, 3, 5, and 7 weeks after crop planting (WAP) and two control treatments of weedy and weed-free all season. Selection of grass weed species was achieved by controlling broadleaf weeds with a premix of bromoxynil plus pyrasulfutole at a rate of 264 g a.i. ha-1.Grass weeds were controlled using nicosulfuron at a rate of 69 g of a.i. ha-1. The CPWC was significantly different across locations. Row spacing and planting date factors did not influence the CPWC at Clayton. Planting date was a significant factor for the CPWC at Rocky Mount, however row spacing did not have any effect on the CPWC. Results for the CPWC are presented in terms growing degree days (GDD) from the date of crop sowing. The CPWC for grass weeds in grain sorghum at Clayton was from 368 to 849 GDD. The CPWC at Rocky Mount for May-planted grain sorghum was from 405 to 876 GDD, while the CPWC for June-planted grain sorghum ranged from 228 to 1042 GDD. These results demonstrate that cultural and environmental factors may influence the beginning, duration and end of the CPWC.}, journal={FRONTIERS IN AGRONOMY}, author={Contreras, Diego and Leon, Ramon G. and Post, Angela R. and Everman, Wesley J.}, year={2022}, month={Sep} }
 @article{ethridge_locke_everman_jordan_leon_2022, title={Crop physiological considerations for combining variable-density planting to optimize seed costs and weed suppression}, volume={70}, ISSN={0043-1745 1550-2759}, url={http://dx.doi.org/10.1017/wsc.2022.62}, DOI={10.1017/wsc.2022.62}, abstractNote={AbstractHigh crop densities are valuable to increase weed suppression, but growers might be reluctant to implement this practice due to increased seed cost. Because it is also possible to lower planting densities in areas with no or low weed interference risk, the area allocated to each planting density must be optimized considering seed cost and productivity per plant. In this study, the growth and yield of maize (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean [Glycine max (L.) Merr.] were characterized in response to low planting densities and arrangements. The results were used to develop a bioeconomic model to optimize the area devoted to high- and low-density plantings to increase weed suppression without increasing seed cost. Physiological differences seen in each crop varied with the densities tested; however, maize was the only crop that had differences in yield (per area) between densities. When a model to optimize low and high planting densities was used, maize and cotton showed the most plasticity in yield per planted seed (g seed−1) and area of low density to compensate for high-density area unit. Maize grown at 75% planting density compared with the high-planting density (200%) increased yield (g seed−1) by 229%, return by 43%, and profit by 79% while decreasing the low-density area needed to compensate for high-density area. Cotton planted at 25% planting density compared with the 200% planting density increased yield (g seed−1) by 1,099%, return by 46%, and profit by 62% while decreasing the low-density area needed to compensate for high-density area. In contrast, the high morphological plasticity of soybean did not translate into changes in area optimization, as soybean maintained return, profit, and a 1:1 ratio for area compensation. This optimization model could allow for the use of variable planting at large scales to increase weed suppression while minimizing costs to producers.}, number={6}, journal={Weed Science}, publisher={Cambridge University Press (CUP)}, author={Ethridge, Sandra R. and Locke, Anna M. and Everman, Wesley J. and Jordan, David L. and Leon, Ramon G.}, year={2022}, month={Nov}, pages={687–697} }
 @article{oreja_inman_jordan_vann_jennings_leon_2022, title={Effect of cotton herbicide programs on weed population trajectories and frequency of glyphosate-resistant Palmer amaranth (Amaranthus palmeri)}, volume={7}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2022.41}, DOI={10.1017/wsc.2022.41}, abstractNote={AbstractThe adoption of dicamba-resistant cotton (Gossypium hirsutum L.) cultivars allows using dicamba to reduce weed populations across growing seasons. However, the overuse of this tool risks selecting new herbicide-resistant biotypes. The objectives of this research were to determine the population trajectories of several weed species and track the frequency of glyphosate-resistant (GR) Palmer amaranth (Amaranthus palmeri S. Watson) over 8 yr in dicamba-resistant cotton. An experiment was established in North Carolina in 2011, and during the first 4 yr, different herbicide programs were applied. These programs included postemergence applications of glyphosate, alone or with dicamba, with or without residual herbicides. During the last 4 yr, all programs received glyphosate plus dicamba. Biennial rotations of postemergence applications of glyphosate only and glyphosate plus dicamba postemergence with and without preemergence herbicides were also included. Sequential applications of glyphosate plus dicamba were applied to the entire test area for the final 4 yr of the study. No herbicide program was entirely successful in controlling the weed community. Weed population trajectories were different according to species and herbicide program, creating all possible outcomes; some increased, others decreased, and others remained stable. Density of resistant A. palmeri increased during the first 4 yr with glyphosate-only programs (up to 11,739 plants m−2) and decreased a 96% during the final 4 yr, when glyphosate plus dicamba was implemented. This species had a strong influence on population levels of other weed species in the community. Goosegrass [Eleusine indica (L.) Gaertn.] was not affected by A. palmeri population levels and even increased its density in some herbicide programs, indicating that not only herbicide resistance but also reproductive rates and competitive dynamics are critical for determining weed population trajectories under intensive herbicide-based control programs. Frequency of glyphosate resistance reached a maximum of 62% after 4 yr, and those levels were maintained until the end of the experiment.}, journal={WEED SCIENCE}, publisher={Cambridge University Press (CUP)}, author={Oreja, Fernando H. and Inman, Matthew D. and Jordan, David L. and Vann, Matthew and Jennings, Katherine M. and Leon, Ramon G.}, year={2022}, month={Jul} }
 @article{leon_creamer_reberg-horton_franzluebbers_2022, title={Eradication of Commelina benghalensis in a long-term experiment using a multistakeholder governance model: a case of regulatory concerns defeating ecological management success}, volume={15}, ISSN={["1939-747X"]}, url={https://doi.org/10.1017/inp.2022.23}, DOI={10.1017/inp.2022.23}, abstractNote={AbstractTropical spiderwort (Commelina benghalensis L.) is a noxious invasive species and was detected in a long-term experiment in a research farm in Goldsboro, NC. A multistakeholder governance model was used to address the invasion of this species. Regulators insisted on the use of fumigation in all fields, but after intense negotiations, a multi-tier eradication plan was designed and implemented, allowing fumigation outside the long-term experiment and a combination of integrated approaches (including physical removal) and intense monitoring and mapping for long-term experimental fields. In the long-term experiment, C. benghalensis populations decreased logarithmically from more than 50,000 plants in approximately 80 ha in 2005 to 19 plants in less than 1 ha in 2019, with a projection of full eradication by 2024. Despite these results, which were considered to be proof of successful ecological management by university researchers, regulators decided to fumigate the fields containing the remaining 19 plants. This decision was made because regulators considered factors such as professional liability and control efficacy. This created serious disagreements between the different stakeholders who participated in the design of the original plan. Despite the goodwill all parties exhibited at the beginning of the governance process, there were important shortcomings that likely contributed to the disagreements at the end. For example, the plan did not include specific milestones, and there was no clarity about what acceptable progress was based on (i.e., plant numbers or the rate of population decline). Also, no financial limits were established, which made administrators concerned about the financial burden the eradication program had become over time. Multistakeholder governance can effectively address plant invasions, but proper definition of progress and the point at which the program must be modified are critical for success, and all this must be done within a governance model that balances power in the decision-making process.}, number={3}, journal={INVASIVE PLANT SCIENCE AND MANAGEMENT}, author={Leon, Ramon G. and Creamer, Nancy and Reberg-Horton, S. Chris and Franzluebbers, Alan J.}, year={2022}, month={Sep}, pages={152–159} }
 @article{camacho_gannon_ahmed_mulvaney_heitman_amoozegar_leon_2022, title={Evaluation of imazapic and flumioxazin carryover risk for Carinata (Brassica carinata) establishment}, volume={5}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2022.27}, DOI={10.1017/wsc.2022.27}, abstractNote={AbstractCarinata (Brassica carinata A. Braun) is a potential crop for biofuel production, but the risk of injury resulting from carryover of soil herbicides used in rotational crops is of concern. The present study evaluated the carryover risk of imazapic and flumioxazin for carinata. Label rates of imazapic (70 g ai ha−1) and flumioxazin (107 g ai ha−1) were applied 24, 18, 12, 6, and 3 mo before carinata planting (MBP). The same herbicides were applied preemergence right after carinata planting at 1X, 0.5X, 0.25X, 0.125X, 0.063X, and 0X the label rate. When either herbicide was applied earlier than 3 MBP, there was no difference in plant density compared with the nontreated control. Carinata damage was <25% when flumioxazin or imazapic was applied at least 6 MBP in Clayton, NC (sandy loam soil), while in Jackson Springs, NC (coarser-textured soil and higher precipitation), at least 12 MPB were needed to lower plant damage to <25%. Preemergence application of 0.063X each herbicide decreased plant density by 40%, with damage reaching >25%. Quantification of herbicide residues in both soils showed that imazapic moved deeper in the soil profile than flumioxazin. This was more evident in Jackson Springs, where 0.68, 3.52, and 7.77 ng of imazapic g−1 soil were detected (15- to 20-cm depth) when the herbicide was applied at 12, 6 and 3 MBP, respectively, while no flumioxazin residues were detected at the same soil depths and times. When residues were 7.78 and 6.90 ng herbicide g−1 soil in the top 10 cm of soil for imazapic and flumioxazin, respectively, carinata exhibited at least 25% damage. Rotational intervals to avoid imazapic and flumioxazin damage to carinata should be between 6 and 12 MBP depending on soil type and environmental conditions, with longer intervals for the former than the latter.}, journal={WEED SCIENCE}, publisher={Cambridge University Press (CUP)}, author={Camacho, Manuel E. and Gannon, Travis W. and Ahmed, Khalied A. and Mulvaney, Michael J. and Heitman, Joshua L. and Amoozegar, Aziz and Leon, Ramon G.}, year={2022}, month={May} }
 @article{chandra_leon_2022, title={Genome-Wide Evolutionary Analysis of Putative Non-Specific Herbicide Resistance Genes and Compilation of Core Promoters between Monocots and Dicots}, volume={13}, ISSN={["2073-4425"]}, url={https://doi.org/10.3390/genes13071171}, DOI={10.3390/genes13071171}, abstractNote={Herbicides are key weed-control tools, but their repeated use across large areas has favored the evolution of herbicide resistance. Although target-site has been the most prevalent and studied type of resistance, non-target-site resistance (NTSR) is increasing. However, the genetic factors involved in NTSR are widely unknown. In this study, four gene groups encoding putative NTSR enzymes, namely, cytochrome-P450, glutathione-S-transferase (GST), uridine 5′-diphospho-glucuronosyltransferase (UDPGT), and nitronate monooxygenase (NMO) were analyzed. The monocot and dicot gene sequences were downloaded from publicly available databases. Phylogenetic trees revealed that most of the CYP450 resistance-related sequences belong to CYP81 (5), and in GST, most of the resistance sequences belonged to GSTU18 (9) and GSTF6 (8) groups. In addition, the study of upstream promoter sequences of these NTSR genes revealed stress-related cis-regulatory motifs, as well as eight transcription factor binding sites (TFBS) were identified. The discovered TFBS were commonly present in both monocots and dicots, and the identified motifs are known to play key roles in countering abiotic stress. Further, we predicted the 3D structure for the resistant CYP450 and GST protein and identified the substrate recognition site through the homology approach. Our description of putative NTSR enzymes may be used to develop innovative weed control techniques to delay the evolution of NTSR.}, number={7}, journal={GENES}, author={Chandra, Saket and Leon, Ramon G.}, year={2022}, month={Jul} }
 @article{cahoon_jordan_tranel_york_riggins_seagroves_inman_everman_leon_2022, title={In-field assessment of EPSPS amplification on fitness cost in mixed glyphosate-resistant and glyphosate-sensitive populations of Palmer amaranth (Amaranthus palmeri)}, volume={10}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2022.60}, DOI={10.1017/wsc.2022.60}, abstractNote={AbstractComparing fitness of herbicide-resistant and herbicide-susceptible weed biotypes is important for managing herbicide resistance. Previous research suggests there is little to no fitness penalty from amplification of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene (a mechanism of glyphosate resistance) in Palmer amaranth (Amaranthus palmeri S. Watson) in controlled studies in the greenhouse or growth chamber. A field study was conducted in North Carolina at three locations naturally infested with A. palmeri to determine vegetative, reproductive, and germination fitness of plants with and without EPSPS amplification grown season-long with cotton (Gossypium hirsutum L.). Seed number was not correlated with EPSPS copy number. However, when plants were binned into two groups, those having an EPSPS copy number ≥2 (relative to reference genes) and those having an EPSPS copy number <2, plant fresh weight and seed number were 1.4 and 1.6 times greater, respectively, for plants with fewer than 2 EPSPS copies. Amaranthus palmeri height and seed germination, and yield of cotton, did not differ when comparing the two binned groups. These data suggest that A. palmeri plants with EPSPS amplification are relatively less fit in the absence of glyphosate, but this reduced fitness does not translate into differences in interference with cotton.}, journal={WEED SCIENCE}, author={Cahoon, Charles W. and Jordan, David L. and Tranel, Patrick J. and York, Alan C. and Riggins, Chance and Seagroves, Richard and Inman, Matthew and Everman, Wesley and Leon, Ramon}, year={2022}, month={Oct} }
 @article{oreja_inman_jordan_bardhan_leon_2022, title={Modeling weed community diversity based on species population density dynamics and herbicide use intensity}, volume={138}, ISSN={["1873-7331"]}, DOI={10.1016/j.eja.2022.126533}, abstractNote={Herbicide programs change weed population density as well as weed community composition. The repeated use of a given program can result in a weed community that progressively becomes more difficult to manage or could lose its ability to provide ecosystem services. Simulation of those changes using stochastic models considering population dynamics of multiple species makes it possible to identify a priori potential community changes that might result from the use of a given herbicide program. The objectives of this work were to model the population dynamics of weed species under different herbicide programs and how those dynamics change weed community diversity over time. Weed population dynamics were stochastically modeled along ten years using population growth rate (lambda) for each species under different herbicide programs. Lambda values were obtained from an eight-year long, field experiment, and these were used to parameterize the stochastic ranges for the model for each weed species. Population trajectories were modeled for each individual species over ten years and the results were used to estimate richness, diversity, and evenness for each herbicide use scenario. The repeated use of glyphosate alone had a minimal effect on richness, but it caused a strong reduction in weed diversity and evenness. Programs with more mechanisms of action and the use of both preemergence and postemergence herbicides were slightly more likely to suffer the loss of weed species than programs with single or just a few herbicides. Conversely, the former had a higher probability of maintaining weed diversity and evenness than the latter. According to simulations, losses in weed community diversity are reversible, especially when highly competitive species were eradicated allowing other species with lower lambda to increase their populations. However, the eradication of species with low reproductive rates reduced diversity and evenness. The effects of herbicide programs on the weed community lasted for several years even after those programs were modified indicating that seed banks play a major buffering role in the rate of change of weed community composition. Thus, frequent changes in management interrupting the repeated use of specific weed control programs, even under high herbicide intensity use (i.e., number of applications and mechanisms of action), can help maintain weed diversity in agroecosystems.}, journal={EUROPEAN JOURNAL OF AGRONOMY}, author={Oreja, Fernando H. and Inman, Matthew D. and Jordan, David L. and Bardhan, Deepayan and Leon, Ramon G.}, year={2022}, month={Aug} }
 @article{dobbs_ginn_skovsen_bagavathiannan_mirsky_reberg-horton_leon_2022, title={New directions in weed management and research using 3D imaging}, volume={10}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2022.56}, DOI={10.1017/wsc.2022.56}, abstractNote={AbstractRecent innovations in 3D imaging technology have created unprecedented potential for better understanding weed responses to management tactics. Although traditional 2D imaging methods for mapping weed populations can be limited in the field by factors such as shadows and tissue overlap, 3D imaging mitigates these challenges by using depth data to create accurate plant models. Three-dimensional imaging can be used to generate spatiotemporal maps of weed populations in the field and target weeds for site-specific weed management, including automated precision weed control. This technology will also help growers monitor cover crop performance for weed suppression and detect late-season weed escapes for timely control, thereby reducing seedbank persistence and slowing the evolution of herbicide resistance. In addition to its many applications in weed management, 3D imaging offers weed researchers new tools for understanding spatial and temporal heterogeneity in weed responses to integrated weed management tactics, including weed–crop competition and weed community dynamics. This technology will provide simple and low-cost tools for growers and researchers alike to better understand weed responses in diverse agronomic contexts, which will aid in reducing herbicide use, mitigating herbicide-resistance evolution, and improving environmental health.}, journal={WEED SCIENCE}, author={Dobbs, April M. and Ginn, Daniel and Skovsen, Soren Kelstrup and Bagavathiannan, Muthukumar V and Mirsky, Steven B. and Reberg-Horton, Chris S. and Leon, Ramon G.}, year={2022}, month={Oct} }
 @article{sosinski_castillo_kulesza_leon_2022, title={Poultry litter and nitrogen fertilizer effects on productivity and nutritive value of crabgrass}, volume={9}, ISSN={["1435-0653"]}, url={https://doi.org/10.1002/csc2.20815}, DOI={10.1002/csc2.20815}, abstractNote={AbstractCrabgrass (Digitaria spp.) is deemed as a productive and nutritious warm‐season annual forage for livestock in the U.S. transition zone. However, there is limited information about nitrogen (N) source and rate effects on productivity and nutritive value of crabgrass in North Carolina. Herbage accumulation (HA), N removal, crude protein (CP), total digestible nutrients (TDN), and tissue nitrate (NO3−) concentrations were evaluated for 2 yr (2020 and 2021) in two physiographic regions (Piedmont and Coastal Plain). Treatments were five rates of chemical N fertilizer (up to 480 kg N ha−1), five rates of plant‐available N from broiler poultry litter (up to 472 and 399 kg N ha−1 in 2020 and 2021, respectively), and one control (zero N). Overall crabgrass responses were not different between N sources. At Coastal Plain, HA increased from 4,990 kg dry matter (DM) ha−1 and plateaued at 7,136 kg DM ha−1 at an agronomic optimum N rate (AONR) of 198 (SE = 49) kg N ha−1. At Piedmont, HA responses were erratic, estimation of an AONR was not possible, and HA values were approximately half or less to those at Coastal Plain. Removal of N was linearly associated with HA. Increasing N rate had a marginal positive effect on CP (ranged from 126 to 154 g kg−1) and no effect on TDN (averaged 626 g kg−1). Tissue NO3− values were below the toxic threshold for feeding livestock. Poultry litter is an effective N source for crabgrass. Nitrogen rate effects were more apparent on crabgrass’ productivity; nutritive value was generally high regardless of N rate and source.}, journal={CROP SCIENCE}, author={Sosinski, Stephanie and Castillo, Miguel S. and Kulesza, Stephanie and Leon, Ramon}, year={2022}, month={Sep} }
 @article{ethridge_locke_everman_jordan_leon_2022, title={Response of Maize, Cotton, and Soybean to Increased Crop Density in Heterogeneous Planting Arrangements}, volume={12}, ISSN={2073-4395}, url={http://dx.doi.org/10.3390/agronomy12051238}, DOI={10.3390/agronomy12051238}, abstractNote={The reduction of row spacing and increase of crop population density are important tools for maximizing crop yield. For this strategy to be effective, the crop population should not create intraspecific crop competition that penalizes yield. Thus, planting arrangements that increase light interception throughout the canopy without increasing row spacing might be needed to maintain yield. In this study, heterogeneous planting arrangements on evenly spaced rows were analyzed for maize (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean (Glycine max (L.) Merr.). Each crop had four planting arrangements: (1) normal density in all rows, considered the control, (2) doubled density in all rows, (3) a sequential arrangement of normal and tripled densities (each in every other row; NTNT), and (4) normal-tripled-tripled-normal (NTTN). Maize and cotton did not exhibit changes in growth and architecture when comparing uniform and variable planting arrangements. Soybeans were more adaptable and increased biomass production by 44% to 45% in variable arrangements. None of the crops showed differences in yield due to planting arrangement, so the use of rows with different densities might not be needed when using high densities to maximize yield.}, number={5}, journal={Agronomy}, publisher={MDPI AG}, author={Ethridge, Sandra R. and Locke, Anna M. and Everman, Wesley J. and Jordan, David L. and Leon, Ramon G.}, year={2022}, month={May}, pages={1238} }
 @article{jones_cahoon_leon_everman_2022, title={Surveying stakeholder's perception of glufosinate and use in North Carolina}, volume={5}, ISSN={["1550-2740"]}, url={https://doi.org/10.1017/wet.2022.31}, DOI={10.1017/wet.2022.31}, abstractNote={AbstractGlufosinate is among the few remaining effective herbicides for postemergence weed control in North Carolina crops. The evolution of glufosinate resistance in key weeds is currently not widespread in North Carolina, but to better assess the current status of glufosinate effectiveness, surveys were distributed at Extension meetings in 2019 and 2020. The surveys were designed to provide information about North Carolina farmers’ perception of glufosinate and its use. Survey results indicate that many North Carolina farmers (≥26%) apply glufosinate at the correct timing (5- to 10-cm weeds). In addition, North Carolina farmers (≥22%) are applying glufosinate as a complementary herbicide to other efficacious herbicides and to control herbicide-resistant weeds, suggesting that glufosinate is part of a diverse chemical weed management plan. Conversely, survey findings indicated that some farmers (13% to 17%) rely exclusively on glufosinate for weed control. Additionally, 28% to 30% of farmers reported glufosinate control failures, and control failures were observed on several weed species among corn, cotton, and soybean crops. The results of the survey suggest that most North Carolina farmers are currently stewarding glufosinate, but they also support the need for Extension personnel to keep educating farmers on how to correctly use glufosinate to delay the evolution of glufosinate-resistant weeds. Semiannual surveys should be distributed to monitor where glufosinate control failures occur and the weed species not being controlled.}, journal={WEED TECHNOLOGY}, author={Jones, Eric A. L. and Cahoon, Charles W. and Leon, Ramon G. and Everman, Wesley J.}, year={2022}, month={May} }
 @article{sapkota_popescu_rajan_leon_reberg-horton_mirsky_bagavathiannan_2022, title={Use of synthetic images for training a deep learning model for weed detection and biomass estimation in cotton}, volume={12}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-022-23399-z}, abstractNote={AbstractSite-specific treatment of weeds in agricultural landscapes has been gaining importance in recent years due to economic savings and minimal impact on the environment. Different detection methods have been developed and tested for precision weed management systems, but recent developments in neural networks have offered great prospects. However, a major limitation with the neural network models is the requirement of high volumes of data for training. The current study aims at exploring an alternative approach to the use of real images to address this issue. In this study, synthetic images were generated with various strategies using plant instances clipped from UAV-borne real images. In addition, the Generative Adversarial Networks (GAN) technique was used to generate fake plant instances which were used in generating synthetic images. These images were used to train a powerful convolutional neural network (CNN) known as "Mask R-CNN" for weed detection and segmentation in a transfer learning mode. The study was conducted on morningglories (MG) and grass weeds (Grass) infested in cotton. The biomass for individual weeds was also collected in the field for biomass modeling using detection and segmentation results derived from model inference. Results showed a comparable performance between the real plant-based synthetic image (mean average precision for mask-mAPm: 0.60; mean average precision for bounding box-mAPb: 0.64) and real image datasets (mAPm: 0.80; mAPb: 0.81). However, the mixed dataset (real image  + real plant instance-based synthetic image dataset) resulted in no performance gain for segmentation mask whereas a very small performance gain for bounding box (mAPm: 0.80; mAPb: 0.83). Around 40–50 plant instances were sufficient for generating synthetic images that resulted in optimal performance. Row orientation of cotton in the synthetic images was beneficial compared to random-orientation. Synthetic images generated with automatically-clipped plant instances performed similarly to the ones generated with manually-clipped instances. Generative Adversarial Networks-derived fake plant instances-based synthetic images did not perform as effectively as real plant instance-based synthetic images. The canopy mask area predicted weed biomass better than bounding box area with R2values of 0.66 and 0.46 for MG and Grass, respectively. The findings of this study offer valuable insights for guiding future endeavors oriented towards using synthetic images for weed detection and segmentation, and biomass estimation in row crops.}, number={1}, journal={SCIENTIFIC REPORTS}, author={Sapkota, Bishwa B. and Popescu, Sorin and Rajan, Nithya and Leon, Ramon G. and Reberg-Horton, Chris and Mirsky, Steven and Bagavathiannan, Muthukumar V}, year={2022}, month={Nov} }
 @article{reinhardt piskackova_leon_2022, title={Using weed emergence and phenology models to determine critical control windows for winter-grown carinata (Brassica carinata)}, volume={6}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2022.30}, DOI={10.1017/wsc.2022.30}, abstractNote={AbstractAdoption of the new biofuel crop carinata (Brassica carinata A. Braun) in the southeastern United States will largely hinge on sound agronomic recommendations that can be economically incorporated into and are compatible with existing rotations. Timing of weed control is crucial for yield protection and long-term weed seedbank management, but predictive weed emergence models have not been as widely studied in winter crops for this purpose. In this work, we use observed and predicted emergence of a winter annual weed community to create recommendations for timing weed control according to weed and crop phenology progression. Observed emergence timings for four winter annual weed species in North Carolina were used to validate previously published models developed for winter annual weeds in Florida by accounting for temperature and daylength differences, and this approach explained more than 70% of the variability in observed emergence. Emergence of stinking chamomile (Anthemis cotula L.) and cutleaf evening primrose (Oenothera laciniata Hill.) followed biphasic patterns comparable to wild radish (Raphanus raphanistrum L.), which were predicted with previously published models accounting for 82% and 84% of the variation, respectively. Using the predictive models for weed emergence and carinata growth, critical control windows (CCW) were estimated for Clayton, NC, and Jay, FL, according to different planting dates. The results demonstrated how early planting coincided with the emergence of three competitive winter weeds, but early control could also remove a large proportion of the predicted emergence of these species. The framework for how planting timing will affect winter weed emergence and crop growth will be an instructive decision-making tool to help prepare farmers to manage weeds in carinata, but it could also be useful for weed management planning for other winter crops.}, journal={WEED SCIENCE}, publisher={Cambridge University Press (CUP)}, author={Reinhardt Piskackova, Theresa A. and Leon, Ramon G.}, year={2022}, month={Jun} }
 @article{jones_austin_dunne_cahoon_jennings_leon_everman_2022, title={Utilization of image-based spectral reflectance to detect herbicide resistance in glufosinate-resistant and glufosinate-susceptible plants: a proof of concept}, volume={12}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2022.68}, DOI={10.1017/wsc.2022.68}, abstractNote={AbstractGlufosinate is an effective postemergence herbicide, and overreliance on this herbicide for weed control is likely to increase and select for glufosinate-resistant weeds. Common assays to confirm herbicide resistance are dose–response and molecular sequencing techniques; both can require significant time, labor, unique technical equipment, and a specialized skillset to perform. As an alternative, we propose an image-based approach that uses a relatively inexpensive multispectral sensor designed for unmanned aerial vehicles to measure and quantify surface reflectance from glufosinate-treated leaf disks. Leaf disks were excised from a glufosinate-resistant and glufosinate-susceptible corn (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean [Glycine max (L.) Merr.] varieties and placed into a 24-well plate containing eight different concentrations (0 to 10 mM) of glufosinate for 48 h. Multispectral images were collected after the 48-h incubation period across five discrete wave bands: blue (475 to 507 nm), green (560 to 587 nm), red (668to 682 nm), red edge (717 to 729 nm), and near infrared (842 to 899 nm). The green leaf index (GLI; a metric to measure chlorophyll content) was utilized to determine relationships between measured reflectance from the tested wave bands from the treated leaf disks and the glufosinate concentration. Clear differences of spectral reflectance were observed between the corn, cotton, and soybean leaf disks of the glufosinate-resistant and glufosinate-susceptible varieties at the 10 mM concentration for select wave bands and GLI. Leaf disks from two additional glufosinate-resistant and glufosinate-susceptible varieties of each crop were subjected to a similar assay with two concentrations: 0 and 10 mM. No differences of spectral reflectance were observed from the corn and soybean varieties in all wave bands and the GLI. The leaf disks of the glufosinate-resistant and glufosinate-susceptible cotton varieties were spectrally distinct in the green, blue, and red-edge wave bands. The results provide a basis for rapidly detecting glufosinate-resistant plants via spectral reflectance. Future research will need to determine the glufosinate concentrations, useful wave bands, and susceptible/resistant thresholds for weeds that evolve resistance.}, journal={WEED SCIENCE}, author={Jones, Eric A. L. and Austin, Robert and Dunne, Jeffrey C. and Cahoon, Charles W. and Jennings, Katherine M. and Leon, Ramon G. and Everman, Wesley J.}, year={2022}, month={Dec} }
 @article{goncalves_mcelroy_brown_mccullough_leon_mccarty_2021, title={A granular fertilizer carrier impregnated with metsulfuron injures centipedegrass when applied at excessive rates}, volume={7}, ISSN={["2374-3832"]}, DOI={10.1002/cft2.20091}, abstractNote={AbstractTo understand the observed injury, the objectives of this research were (a) to correlate combination of nitrogen fertilization and metsulfuron [methyl 2‐(4‐methoxy‐6‐methyl‐1,3,5‐triazine‐ 2‐ylcarbamoylsulfamoyl) benzoate] with excessive injury to centipedegrass [Eremochloa ophiuroides (Munro) Hack.] and (b) to determine how simultaneous high nitrogen fertilizer and the resulting increased metsulfuron rates exacerbated the observed injury. Field research was conducted at Auburn University, Clemson University, University of Florida, the University of Georgia, and H&H Sod Company in St. Cloud, FL, in 2015. Treatments included: a nontreated control, fertilizer alone (32–0–10 N–P–K and 32–0–9 N–P–K), metsulfuron (60% water‐dispersible granules), metsulfuron on an inert carrier, metsulfuron on fertilizer (32–0–9 N–P–K), and atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino1,3,5‐triazine) on fertilizer (29–0–10 N–P–K) applied at rates ranging from one to eight times the labeled rate. Metsulfuron on fertilizer induced more injury as the rate increased than any other treatment across all locations. The highest rates of metsulfuron on fertilizer (348.5 lb N acre–1 plus 0.24 lb metsulfuron acre–1) reduced centipedegrass ground cover by 79 and 81% at 28 and 42 d after treatment, respectively.  From these data, we conclude that metsulfuron applied on a granular fertilizer carrier can induce greater injury than metsulfuron on an inert granular carrier.}, number={1}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, author={Goncalves, Clebson G. and McElroy, J. Scott and Brown, Austin M. and McCullough, Patrick E. and Leon, Ramon Gonzalez and McCarty, Lambert B.}, year={2021} }
 @article{gettys_leon_2021, title={A population genetics approach for the study of fluridone resistance in hydrilla}, volume={16}, ISSN={["1818-5487"]}, DOI={10.3391/ai.2021.16.1.03}, abstractNote={Fluridone-resistant hydrilla was first suspected in Florida in 1999 and was confirmed using molecular genetics techniques in 2003. Although the vast majority of species that evolve resistance to herbicides or other stressors do so through the genetic mutations that occur during sexual reproduction, all hydrilla in Florida is of the dioecious pistillate (“female”) biotype and all reproduction and spread is via vegetative means. The Hardy-Weinberg principle of constant allele frequencies (i.e., p + q = 1), used to predict allelic frequency shifts within populations due to selection, is based on a number of assumptions that are violated by species that reproduce asexually. In this paper, we address the assumptions of the model in the context of the clonally propagated species hydrilla and compare theoretical model predictions to the likely timeline of actual events that occurred in many bodies of water in Florida. The generational shifts in within-population allele frequencies from almost exclusively fluridone-susceptible to almost exclusively fluridoneresistant track well with the actual development of fluridone-resistant populations of hydrilla in Florida when considering fitness differences among fluridone resistance alleles after fluridone treatments. The present study illustrates how the Hardy-Weinberg principle of constant allele frequencies can be used as an exploratory tool to model resistance evolution in asexually reproducing species such as hydrilla.}, number={1}, journal={AQUATIC INVASIONS}, author={Gettys, Lyn A. and Leon, Ramon G.}, year={2021}, month={Mar}, pages={28–42} }
 @article{torra_royo-esnal_romano_osuna_leon_recasens_2021, title={Amaranthus palmeri a New Invasive Weed in Spain with Herbicide Resistant Biotypes (vol 10, 993, 2020)}, volume={11}, ISSN={["2073-4395"]}, url={https://doi.org/10.3390/agronomy11071332}, DOI={10.3390/agronomy11071332}, abstractNote={The authors would like to make the following correction to the published paper [...]}, number={7}, journal={AGRONOMY-BASEL}, author={Torra, Joel and Royo-Esnal, Aritz and Romano, Yolanda and Osuna, Maria Dolores and Leon, Ramon G. and Recasens, Jordi}, year={2021}, month={Jul} }
 @article{reyes-cabrera_erickson_leon_2021, title={Biochar affects soil water content but not soybean yield in a sandy southeastern US soil}, volume={4}, ISSN={["2639-6696"]}, url={https://doi.org/10.1002/agg2.20197}, DOI={10.1002/agg2.20197}, abstractNote={AbstractDrought is the greatest abiotic cause of soybean [Glycine max (L.) Merr.] yield loss in rainfed systems in the United States. Preplant incorporation of powdery biochar to soil cultivated with soybean in these water‐stressed regions presents the potential to increase volumetric soil water content (VSWC) between rainfall events and ameliorate the impact of intermittent water stress. However, VSWC and the above‐ and belowground response of soybean to biochar amendment are not well understood. This 2‐yr field study (2014–2015) evaluated the effectiveness of incorporating powdery (325 μm) biochar to 0.2‐m soil depth to increase soil water storage in a coarse‐textured soil in the southeastern United States. Soybean yield, aboveground biomass accumulation, root morphology, and VSWC in the soil profile to 1‐m depth were assessed under three biochar rates (0, 2.5, and 10 Mg ha–1) and two water treatments (rainfed and irrigated). In 2014, application of 10 Mg biochar ha–1 increased the cumulative soil water storage in the top 1‐m soil depth. Biochar application did not affect soybean yield or root morphology. Biochar only elicited changes in fresh weight of pods during reproductive stages, which indicates biochar's limited benefit to the water status of this shoot component. Irrigation increased yield by 28% compared with the rainfed treatment. Our study provides evidence that field application of biochar to soybean may be a sustainable practice to sequester recalcitrant C in the soil when biochar is available to producers, but its benefits on protecting soybean yield from water stress might depend on other factors such as soil texture, rainfall amount, and frequency.}, number={3}, journal={AGROSYSTEMS GEOSCIENCES & ENVIRONMENT}, publisher={Wiley}, author={Reyes-Cabrera, Joel and Erickson, John E. and Leon, Ramon G.}, year={2021} }
 @article{bashyal_mulvaney_lee_wilson_iboyi_leon_landry_boote_2021, title={Brassica carinata biomass, yield, and seed chemical composition response to nitrogen rates and timing on southern Coastal Plain soils in the United States}, volume={6}, ISSN={["1757-1707"]}, DOI={10.1111/gcbb.12846}, abstractNote={AbstractBrassica carinata (carinata), a non‐food oilseed feedstock mainly used for biofuel, is a relatively new alternative winter crop in the southeastern (SE) United States (US). However, there are limited N rate and N application timing data available at the regional scale. These data are needed to expand production in the SE US. An N rate study was conducted during the winter–spring growing seasons during 2017–2018 and 2018–2019 in Florida, US, and at three locations during 2018–2019 in Georgia, US, to quantify the effects of N rate (0, 45, 90, 134, and 179 kg N ha−1) on carinata nutrient uptake, biomass, seed yield, and seed chemical composition. Seed yield showed a linear response up to 134 kg N ha−1. Seed protein and glucosinolate concentrations decreased from 0 to 90 kg N ha−1, then increased from 90 to 179 kg N ha−1. Seed oil concentration was inversely related to seed protein concentration. A two‐factor N application timing study (4 N application timing: at‐plant, pre‐bolting, at‐plant + pre‐bolting, at‐plant + pre‐bolting + bolting × 4 N rates: 0, 45, 90, and 134 kg N ha−1) was conducted in Georgia, US, over three site‐years to quantify the effect of N application timing on yield and agronomic and economic optimum N rates (AONR and EONR, respectively). All split applications increased AONR by at least 10 kg N ha−1 compared to a single at‐plant application. A two‐split N application was more profitable than either a single N application or a three‐split N application based on marginal return. A two‐way split application (at‐plant + pre‐bolting) at 134 kg N ha−1 is recommended to optimize yield and economical production. Based on uncertainty analyses, the 50% credible interval of EONR occurred between 116 and 152 kg N ha−1, with a median estimate at 130 kg N ha−1.}, journal={GLOBAL CHANGE BIOLOGY BIOENERGY}, author={Bashyal, Mahesh and Mulvaney, Michael J. and Lee, Dewey and Wilson, Chris and Iboyi, Joseph E. and Leon, Ramon G. and Landry, Gabriel M. and Boote, Kenneth J.}, year={2021}, month={Jun} }
 @article{ethridge_post_devkota_mulvaney_leon_2021, title={Characterization of carinata tolerance to select herbicides using field dose-response studies}, volume={35}, ISSN={["1550-2740"]}, url={https://doi.org/10.1017/wet.2021.57}, DOI={10.1017/wet.2021.57}, abstractNote={AbstractField experiments were conducted from 2017 to 2019 to determine the tolerance of carinata to several preemergence and postemergence herbicides. Preliminary screenings identified herbicides that caused large variation on carinata injury, indicating the potential for selectivity. Dose-response field studies were conducted to quantify the tolerance of carinata to select herbicides. Diuron applied preemergence at rates of 280 g ai ha−1 or higher reduced carinata population density 54% to 84% compared to the nontreated control. In certain locations, clomazone applied preemergence caused minor injury with an acceptable level of carinata tolerance and only doses above 105 g ai ha−1 caused yield reductions. Napropamide doses of 2,856 g ai ha−1 or higher applied preemergence caused at least 25% injury to carinata; however, the damage was not severe enough to reduce yields. Simazine applied postemergence at rates above 1,594 g ai ha−1 caused 50% or more injury, resulting in yield losses ranging from 0% to 95% depending on location. Clopyralid applied postemergence at 2,512 g ai ha−1 caused 25% injury with relative yield reductions, which varied across locations. The present study identified clomazone and napropamide applied preemergence, and clopyralid applied postemergence as potential herbicides for weed control in carinata. In contrast, diuron, simazine, metribuzin, imazethapyr, and chlorimuron caused high levels of carinata mortality and can be used to control volunteer carinata plants in rotational crops.}, number={6}, journal={WEED TECHNOLOGY}, publisher={Cambridge University Press (CUP)}, author={Ethridge, Sandra R. and Post, Angela and Devkota, Pratap and Mulvaney, Michael J. and Leon, Ramon G.}, year={2021}, month={Dec}, pages={957–966} }
 @article{piskackova_reberg‐horton_richardson_jennings_franca_young_leon_2021, title={Cover Image}, volume={61}, url={https://doi.org/10.1111/wre.12490}, DOI={10.1111/wre.12490}, abstractNote={The cover image is based on the Original Article Windows of action for controlling palmer amaranth (Amaranthus palmeri) using emergence and phenology models by Theresa A. Reinhardt Piskackova et al., https://doi.org/10.1111/wre.12470.}, number={3}, journal={Weed Research}, publisher={Wiley}, author={Piskackova, Theresa A. Reinhardt and Reberg‐Horton, Samuel Chris and Richardson, Robert J. and Jennings, Katie M. and Franca, Lucas and Young, Bryan G. and Leon, Ramon G.}, year={2021}, month={Jun} }
 @article{tiwari_reinhardt piskackova_devkota_mulvaney_ferrell_leon_2021, title={Emergence patterns of winter and summer annual weeds in Ethiopian mustard (Brassica carinata) cropping system}, volume={69}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2021.20}, DOI={10.1017/wsc.2021.20}, abstractNote={Abstract
	  Ethiopian mustard (Brassica carinata A. Braun) is a biofuel crop recently introduced in the southeastern United States. For this crop to be successful, integrated weed management strategies that complement its rotation with summer cash crops must be developed. The objectives of this research were to evaluate the effect of previous season summer crops on winter weed emergence patterns during Ethiopian mustard growing season and to assess the impact of planting Ethiopian mustard on the emergence patterns of summer weed species. Gompertz models were fit to winter and summer weed emergence patterns. All models represented more than 80% of the variation, with root mean-square error values less than 0.20. The emergence pattern for winter weed species was best described using growing degree-day accumulation, and this model can be utilized for implementing weed control strategies at the critical Ethiopian mustard growth stages. The results also showed that summer weeds can emerge during the winter in northern Florida but do not survive frost damage, which might create off-season seedbank reductions before the summer crop growing season.}, number={4}, journal={WEED SCIENCE}, publisher={Cambridge University Press (CUP)}, author={Tiwari, Ruby and Reinhardt Piskackova, Theresa A. and Devkota, Pratap and Mulvaney, Michael J. and Ferrell, Jason A. and Leon, Ramon G.}, year={2021}, month={Jul}, pages={446–453} }
 @article{moore_jennings_monks_jordan_leon_boyette_2021, title={Evaluating shade cloth to simulate Palmer amaranth (Amaranthus palmeri) competition in sweetpotato}, volume={69}, ISSN={["1550-2759"]}, DOI={10.1017/wsc.2021.21}, abstractNote={AbstractField studies were conducted in 2019 and 2020 to compare the effects of shade cloth light interception and Palmer amaranth (Amaranthus palmeriS. Watson) competition on ‘Covington’ sweetpotato [Ipomoea batatas(L.) Lam.]. Treatments consisted of a seven by two factorial arrangement, in which the first factor included shade cloth with an average measured light interception of 41%, 59%, 76%, and 94% andA. palmerithinned to 0.6 or 3.1 plants m−2or a nontreated weed-free check; and the second factor included shade cloth orA. palmeriremoval timing at 6 or 10 wk after planting (WAP).Amaranthus palmerilight interception peaked around 710 to 840 growing degree days (base 10 C) (6 to 7 WAP) with a maximum light interception of 67% and 84% for the 0.6 and 3.1 plants m−2densities, respectively. Increasing shade cloth light interception by 1% linearly increased yield loss by 1% for No. 1, jumbo, and total yield. Yield loss increased by 36%, 23%, and 35% as shade cloth removal was delayed from 6 to 10 WAP for No. 1, jumbo, and total yield, respectively.F-tests comparing reduced versus full models of yield loss provided no evidence that the presence of yield loss fromA. palmerilight interception caused yield loss different than that explained by the shade cloth at similar light-interception levels. Results indicate that shade cloth structures could be used to simulate Covington sweetpotato yield loss fromA. palmericompetition, and light interception could be used as a predictor for expected yield loss fromA. palmericompetition.}, number={4}, journal={WEED SCIENCE}, author={Moore, Levi D. and Jennings, Katherine M. and Monks, David W. and Jordan, David L. and Leon, Ramon G. and Boyette, Michael D.}, year={2021}, month={Jul}, pages={478–484} }
 @article{moore_jennings_monks_leon_boyette_jordan_2021, title={Influence of herbicides on germination and quality of Palmer amaranth (Amaranthus palmeri) seed}, volume={35}, ISSN={["1550-2740"]}, DOI={10.1017/wet.2021.71}, abstractNote={AbstractLaboratory and greenhouse studies were conducted to evaluate the effects of chemical treatments applied to Palmer amaranth seeds or gynoecious plants that retain seeds to determine seed germination and quality. Treatments applied to physiologically mature Palmer amaranth seed included acifluorfen, dicamba, ethephon, flumioxazin, fomesafen, halosulfuron, linuron, metribuzin, oryzalin, pendimethalin, pyroxasulfone, S-metolachlor, saflufenacil, trifluralin, and 2,4-D plus crop oil concentrate applied at 1× and 2× the suggested use rates from the manufacturer. Germination was reduced by 20% when 2,4-D was used, 15% when dicamba was used, and 13% when halosulfuron and pyroxasulfone were used. Use of dicamba, ethephon, halosulfuron, oryzalin, trifluralin, and 2,4-D resulted in decreased seedling length by an average of at least 50%. Due to the observed effect of dicamba, ethephon, halosulfuron, oryzalin, trifluralin, and 2,4-D, these treatments were applied to gynoecious Palmer amaranth inflorescence at the 2× registered application rates to evaluate their effects on progeny seed. Dicamba use resulted in a 24% decrease in seed germination, whereas all other treatment results were similar to those of the control. Crush tests showed that seed viability was greater than 95%, thus dicamba did not have a strong effect on seed viability. No treatments applied to Palmer amaranth inflorescence affected average seedling length; therefore, chemical treatments did not affect the quality of seeds that germinated.}, number={5}, journal={WEED TECHNOLOGY}, author={Moore, Levi D. and Jennings, Katherine M. and Monks, David W. and Leon, Ramon G. and Boyette, Michael D. and Jordan, David L.}, year={2021}, month={Oct}, pages={786–789} }
 @article{maia_shaddox_leon_unruh_2021, title={Nitrogen leaching and Tifway bermudagrass response to simultaneous nutrient and pre-emergence herbicide applications}, volume={11}, ISSN={["1537-2537"]}, DOI={10.1002/jeq2.20297}, abstractNote={AbstractPre‐emergence (PRE) herbicides are commonly applied simultaneously with fertilizers to turfgrass; however, the influence of PRE herbicides on nitrogen (N) uptake and leaching from turfgrass remains unclear. The hypothesis of this study was that PRE herbicides applied simultaneously with N fertilizers increase N leaching from Tifway 419 bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy, ‘Tifway’] above that from fallow soil. A nutrient leaching study was conducted from June 2017 through June 2019 in Fort Lauderdale, FL. Treatments consisted of indaziflam (25 g a.i. ha–1), prodiamine (540 g a.i. ha–1), and oxadiazon (4,480 g a.i. ha–1); a nontreated turfgrass control (turfgrass fertilized but not treated with PRE herbicides); and a fallow soil. Fertilizer (15–2–12) was applied every 60 d at 49 kg N ha–1, and PRE herbicides were applied every 120 d. Pre‐emergence herbicides resulted in a 3.6‐ and 5.5‐fold increases in NO3–N concentration compared with fallow soil during June 2017 and January 2018, respectively, whereas fallow soil resulted in increased NO3–N concentration during 10 mo and ranged from 3.8‐ to 15‐fold greater than that from turfgrass plots. Turfgrass plots resulted in reduced N leaching of ∼7% during 5 mo compared with fallow soil and did not result in increased N leaching during any month. Cumulative N leached from turfgrass plots ranged from 75 to 120 kg ha–1 and did not differ from fallow soil. Turfgrass growth rate and N uptake were not influenced by PRE herbicide. The results indicated that fertilizers applied with PRE herbicides does not result in increased N leaching or reduced N uptake.}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Maia, Lucas O. R. and Shaddox, Travis W. and Leon, Ramon G. and Unruh, J. Bryan}, year={2021}, month={Nov} }
 @article{mahoney_jordan_hare_leon_roma-burgos_vann_jennings_everman_cahoon_2021, title={Palmer Amaranth (Amaranthus palmeri) Growth and Seed Production When in Competition with Peanut and Other Crops in North Carolina}, volume={11}, ISSN={["2073-4395"]}, url={https://doi.org/10.3390/agronomy11091734}, DOI={10.3390/agronomy11091734}, abstractNote={Palmer amaranth (Amaranthus palmeri S. Wats.) is a highly competitive weed that can be difficult to manage in many cropping systems. Research to date has not quantified the growth and development of A. palmeri in a manner that allows direct comparisons across cropping systems. Research was conducted to compare the growth, development, and seed production of A. palmeri when competing with corn (Zea mays L.), cotton (Gossypium hirsutum L.), peanut (Arachis hypogaea L.), and soybean [Glycine max (L.) Merr.] when emerging with crops or emerging three weeks after crops emerge. Regardless of when A. palmeri emerged, seed production was greatest and similar in cotton and peanut and exceeded that of corn and soybean; seed production in soybean exceeded that of corn. However, seed production was approximately 10-fold greater when A. palmeri emerged with crops compared with emergence three weeks later. These results illustrate the importance of controlling weeds during the first three weeks of the season relative to contributions of A. palmeri to the weed seed bank and is the first report comparing seed production in presence of these crops in a manner allowing a statistical comparison of seed production and highlighting the importance of crop sequence for seed bank management.}, number={9}, journal={AGRONOMY-BASEL}, publisher={MDPI AG}, author={Mahoney, Denis J. and Jordan, David L. and Hare, Andrew T. and Leon, Ramon G. and Roma-Burgos, Nilda and Vann, Matthew C. and Jennings, Katherine M. and Everman, Wesley J. and Cahoon, Charles W.}, year={2021}, month={Sep} }
 @article{leon_laat_2021, title={Population and quantitative genetic analyses of life-history trait adaptations in Amaranthus palmeri S. Watson}, volume={7}, ISSN={["1365-3180"]}, url={https://doi.org/10.1111/wre.12492}, DOI={10.1111/wre.12492}, abstractNote={AbstractAmaranthus palmeri populations can evolve life‐history traits despite its high levels of genetic diversity and gene flow. However, it was not known whether those differences were due to selection or other evolutionary processes. We used microsatellite markers to quantify genetic differentiation among 10 Amaranthus palmeri populations and determined whether the differences in life‐history traits among the populations could be attributed to selection. Genetic differentiation was small (ΦST = 0.093), indicating that there were high rates of gene flow among populations. AMOVA showed that only 9% of the genetic variability was explained by variation among populations and 90% was found within populations. Using ΦST as a surrogate for FST in the QST−FST analysis, we confirmed that most traits followed the same pattern as neutral markers and were not under selection. However, important traits for weediness such as plant height, dry weight and nitrogen use efficiency were under selection. These results provide evidence that selection forces in agroecosystems can increase weediness in A. palmeri, and that those forces should be identified to develop strategies to counter them when possible.}, journal={WEED RESEARCH}, author={Leon, Ramon G. and Laat, Rocio}, year={2021}, month={Jul} }
 @article{oreja_inman_jordan_leon_2021, title={Population growth rates of weed species in response to herbicide programme intensity and their impact on weed community}, volume={9}, ISSN={["1365-3180"]}, url={https://doi.org/10.1111/wre.12509}, DOI={10.1111/wre.12509}, abstractNote={AbstractThe adoption of dicamba‐tolerant crops has reduced the challenge of controlling glyphosate‐resistantAmaranthus palmeriin these crops. However, introducing herbicide programmes with new mechanisms of action and different intensities can favour major shifts in weed communities. This can affect not only the functionality of the agroecosystem, but also resource availability to the most problematic species. The objectives of this work were to evaluate how herbicide programme structure and intensity affect (a) weed diversity, (b) population growth rate (λ) of weed species and (c) weed community structure based on λ dynamics in a dicamba‐tolerant cotton monoculture. To achieve these objectives, a cotton field experiment was established to compare four herbicide programmes from 2011 to 2018. The herbicide programmes differed in the first 4 years (i.e. glyphosate every year, alternating glyphosate and glyphosate plus dicamba every other year, glyphosate plus dicamba every year, and residual herbicide and glyphosate plus dicamba every year). During the last 4 years, all programmes received glyphosate plus dicamba. The weed seedbank was evaluated every spring and λ calculated. Environmental variation from year to year was more important in determining weed richness than herbicide programmes, which exhibited similar richness across all treatments during the eight years of the study. Regardless of herbicide programme, most species maintained λ between zero and one. Only a few species were the exception with λ values above one, such asA.palmeri,Mollugo verticillataandEleusine indica. Although glyphosate plus dicamba reduced λ for several species, this herbicide mix was less effective in reducing λ for other weeds compared with glyphosate alone, suggesting a potential antagonism that could change weed community composition. The limited changes in λ for most species suggest the capacity of weeds to adjust reproduction and survival to overcome changes in mortality rates caused by increases in herbicide use intensity.}, journal={WEED RESEARCH}, publisher={Wiley}, author={Oreja, Fernando H. and Inman, Matthew D. and Jordan, David L. and Leon, Ramon G.}, year={2021}, month={Sep} }
 @article{moore_jennings_monks_leon_jordan_boyette_2021, title={Safety and efficacy of linuron with or without an adjuvant or S-metolachlor for POST control of Palmer amaranth (Amaranthus palmeri) in sweetpotato}, volume={35}, ISSN={["1550-2740"]}, DOI={10.1017/wet.2021.27}, abstractNote={AbstractField studies were conducted to evaluate linuron for POST control of Palmer amaranth in sweetpotato to minimize reliance on protoporphyrinogen oxidase (PPO)-inhibiting herbicides. Treatments were arranged in a two by four factorial in which the first factor consisted of two rates of linuron (420 and 700 g ai ha−1), and the second factor consisted of linuron applied alone or in combinations of linuron plus a nonionic surfactant (NIS; 0.5% vol/vol), linuron plus S-metolachlor (800 g ai ha−1), or linuron plus NIS plus S-metolachlor. In addition, S-metolachlor alone and nontreated weedy and weed-free checks were included for comparison. Treatments were applied to ‘Covington’ sweetpotato 8 d after transplanting (DAP). S-metolachlor alone provided poor Palmer amaranth control because emergence had occurred at applications. All treatments that included linuron resulted in at least 98% and 91% Palmer amaranth control 1 and 2 wk after treatment (WAT), respectively. Including NIS with linuron did not increase Palmer amaranth control compared to linuron alone, but it resulted in greater sweetpotato injury and subsequently decreased total sweetpotato yield by 25%. Including S-metolachlor with linuron resulted in the greatest Palmer amaranth control 4 WAT, but increased crop foliar injury to 36% 1 WAT compared to 17% foliar injury from linuron alone. Marketable and total sweetpotato yields were similar between linuron alone and linuron plus S-metolachlor or S-metolachlor plus NIS treatments, though all treatments resulted in at least 39% less total yield than the weed-free check resulting from herbicide injury and/or Palmer amaranth competition. Because of the excellent POST Palmer amaranth control from linuron 1 WAT, a system that includes linuron applied 7 DAP followed by S-metolachlor applied 14 DAP could help to extend residual Palmer amaranth control further into the critical period of weed control while minimizing sweetpotato injury.}, number={3}, journal={WEED TECHNOLOGY}, author={Moore, Levi D. and Jennings, Katherine M. and Monks, David W. and Leon, Ramon G. and Jordan, David L. and Boyette, Michael D.}, year={2021}, month={Jun}, pages={471–475} }
 @article{camacho_heitman_gannon_amoozegar_leon_2021, title={Seed germination responses to soil hydraulic conductivity and polyethylene glycol (PEG) osmotic solutions}, volume={462}, ISSN={["1573-5036"]}, url={https://doi.org/10.1007/s11104-021-04857-5}, DOI={10.1007/s11104-021-04857-5}, number={1-2}, journal={PLANT AND SOIL}, author={Camacho, Manuel E. and Heitman, Joshua L. and Gannon, Travis W. and Amoozegar, Aziz and Leon, Ramon G.}, year={2021}, month={May}, pages={175–188} }
 @article{moore_jennings_monks_jordan_boyette_leon_mahoney_everman_cahoon_2021, title={Susceptibility of Palmer amaranth accessions in North Carolina to atrazine, dicamba, S-metolachlor, and 2,4-D}, volume={11}, ISSN={["2374-3832"]}, url={https://doi.org/10.1002/cft2.20136}, DOI={10.1002/cft2.20136}, abstractNote={Core Ideas
All of the 120 accessions of Palmer amaranth collected in the Coastal Plain of North Carolina were controlled by atrazine and dicamba applied at field use rates in the greenhouse.
Reduced sensitivity among accessions was noted when S‐metolachlor and 2,4‐D were applied to Palmer amaranth at field use rates in the greenhouse.
Additional research is needed to determine if reduced sensitivity of Palmer amaranth to S‐metolachlor and 2,4‐D is associated with evolved resistance.
}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, publisher={Wiley}, author={Moore, Levi D. and Jennings, Katherine M. and Monks, David W. and Jordan, David L. and Boyette, Michael D. and Leon, Ramon G. and Mahoney, Dennis J. and Everman, Wesley J. and Cahoon, Charles W.}, year={2021}, month={Nov} }
 @article{cockson_veazie_davis_barajas_post_crozier_leon_patterson_whipker_2021, title={The Impacts of Micronutrient Fertility on the Mineral Uptake and Growth of Brassica carinata}, volume={11}, ISBN={2077-0472}, url={https://doi.org/10.3390/agriculture11030221}, DOI={10.3390/agriculture11030221}, abstractNote={Many abiotic factors impact the yield and growth of Brassica carinata (commonly referred to as carinata or Ethiopian mustard). Very little is known about carinata and how mineral nutrients impact its growth, and more specifically, the sufficiency values for fertility over the plant’s growth cycle and life stages. This study explored the impacts that plant nutrients, specifically micronutrients, can have on the growth and development of carinata over its distinct life stages (rosette, bolting, flowering, and pod set). Plants were grown under varying micronutrient concentrations (0, 25, 50, 75, 87.5, and 100%) of a modified Hoagland’s solution. Data were collected on plant height, canopy diameter, leaf tissue mineral nutrient concentrations, and biomass. The results demonstrated that micronutrient fertility has profound impacts on the production of Brassica carinata during different life stages. Boron (B) exclusion had the greatest impact on the growth and reproduction of Brassica carinata, with the death of the apical meristem that resulted in a lack of siliques or seeds at the lowest rate. Optimal relative elemental leaf tissue concentrations varied among micronutrient fertility concentrations and life stages. Certain elements exhibited linear increases in nutrient leaf tissue accumulation as solution concentration increased without reaching a maximum concentration during specific life stages. Other life stages and/or elements produced distinct plateau leaf tissue mineral concentrations despite increasing fertility treatment concentrations such as B in the rosette stage (47.2–50.0 mg·kg−1), copper (Cu) (bolting stage at 6.62–7.57 mg·kg−1), zinc (Zn) (bolting stage at 27.47–39.87 and flowering at 33.98–43.50 mg·kg−1), molybdenum (Mo) (flowering stage at 2.42–3.23 mg·kg−1), and manganese (Mn) (bolting stage at 117.03–161.63 mg·kg−1). This work demonstrates that Brassica carinata has different fertility demands and will accumulate differing leaf tissue concentrations during its life stages. This work serves as a baseline for further uptake and portioning work for Brassica carinata.}, number={3}, journal={AGRICULTURE-BASEL}, publisher={MDPI AG}, author={Cockson, Paul and Veazie, Patrick and Davis, Matthew and Barajas, Gabby and Post, Angela and Crozier, Carl R. and Leon, Ramon G. and Patterson, Robert and Whipker, Brian E.}, year={2021}, month={Mar}, pages={221} }
 @article{iboyi_mulvaney_balkcom_seepaul_bashyal_perondi_leon_devkota_small_george_et al._2021, title={Tillage system and seeding rate effects on the performance of Brassica carinata}, volume={13}, ISSN={["1757-1707"]}, DOI={10.1111/gcbb.12809}, abstractNote={AbstractBrassica carinata, a nonfood oilseed crop, is used to produce renewable fuels because of its high oil content and favorable fatty acid profile. Production in the southeastern United States is relatively new, and information on agronomic management practices to optimize growth and yield is limited. Since optimal seeding rate may depend on the land preparation method for this small‐seeded crop, a study was conducted to evaluate the effect of tillage system (conventional, no‐till, broadcast‐disc, and ripper‐roller) and seeding rate (1.12, 5.60, 10.09, and 14.57 kg seed ha−1) on the performance of B. carinata. A randomized complete block design with a strip‐plot restriction on randomization and four replications was implemented in Headland, AL, Jay, FL, and Quincy, FL, over five site‐years during the 2017–2018 and 2018–2019 growing seasons. Data were collected on soil residue cover; plant population; soil penetrometer resistance and moisture; biomass (including carbon and nitrogen); stalk diameter; yield and yield components; seed oil, protein, and glucosinolates concentration; and oil composition. Soil penetrometer resistance was significantly affected by tillage system, with the ripper‐roller consistently having the lowest penetration resistance values across all site‐years. Ripper‐roller tillage had the highest oil content and lowest protein and glucosinolate contents. Yield response to tillage system was variable. Among seeding rate treatments, yield was lowest at 1.12 kg seed ha−1 and similar among 5.60, 10.09, and 14.57 kg seed ha−1 at all site‐years. There was no tillage by seeding rate interaction for yield. Results indicate that among seeding rate treatments used, 5.6 kg seed ha−1 rate was optimal at all site‐years regardless of land preparation method and is thus the recommended seeding rate for commercial carinata production in the Southeastern United States.}, number={4}, journal={GLOBAL CHANGE BIOLOGY BIOENERGY}, author={Iboyi, Joseph E. and Mulvaney, Michael J. and Balkcom, Kipling S. and Seepaul, Ramdeo and Bashyal, Mahesh and Perondi, Daniel and Leon, Ramon G. and Devkota, Pratap and Small, Ian M. and George, Sheeja and et al.}, year={2021}, month={Apr}, pages={600–617} }
 @article{reinhardt piskackova_reberg-horton_richardson_jennings_franca_young_leon_2021, title={Windows of action for controlling palmer amaranth (Amaranthus palmeri) using emergence and phenology models}, volume={61}, ISSN={["1365-3180"]}, url={https://doi.org/10.1111/wre.12470}, DOI={10.1111/wre.12470}, abstractNote={AbstractAmaranthus palmeri S. Watson is a competitive weed native to North America with many herbicide‐resistant biotypes that have been spreading around the world. Due to its fast growth, farmers need to optimise control timing to reduce the risk of escapes. This study tracked A. palmeri emergence and phenology using days or growing degree days (GDD, Tbase = 15°C; thermal time or hydrothermal time). While A. palmeri has been observed emerging throughout the summer growing season, this study found that 90% of total season A. palmeri emerged before July in the absence of a crop canopy. Using thermal time, emergence could be predicted in different locations and years: reaching 10%, 50% and 90% at 77, 278 and 593 GDD from January 1, respectively. From the time of emergence, 10% of A. palmeri were 10 cm tall after 148 GDD, showed first signs of inflorescence by 212 GDD, and open florets by 419 GDD. Also, 50% of A. palmeri plants had reached the respective stages by 244, 394 and 796 GDD. Using the probability of A. palmeri to reach different phenological stages over time as a function of emergence prediction, critical control windows were determined based on thresholds for risk of escapes. Many tactics and times of action are important for managing this weed. Information about A. palmeri biology indicates these actions could be timed more effectively using weather data and predictive models.}, number={3}, journal={WEED RESEARCH}, author={Reinhardt Piskackova, Theresa A. and Reberg-Horton, Samuel Chris and Richardson, Robert J. and Jennings, Katie M. and Franca, Lucas and Young, Bryan G. and Leon, Ramon G.}, year={2021}, month={Jun}, pages={188–198} }
 @article{torra_royo-esnal_romano_osuna_león_recasens_2020, title={Amaranthus palmeri a New Invasive Weed in Spain with Herbicide Resistant Biotypes}, volume={10}, url={https://doi.org/10.3390/agronomy10070993}, DOI={10.3390/agronomy10070993}, abstractNote={Amaranthus palmeri is the most prominent invasive weed in agricultural land from North America, partly due to its propensity to evolve resistance to multiple herbicide sites of action. In the last two decades, reports of this species have increased throughout the American continent and occasionally in other continents. In 2007, A. palmeri populations were found in three localities in northeastern Spain, and they are still present today. To determine whether these three populations resulted from a common or independent introduction events—and when and from where they could have occurred—research was carried out aiming to characterize the resistance profile and mechanisms to 5-enolpyruvylshikimate-3-phosphate synthase-and acetolactate synthase (ALS)-inhibiting herbicides and to analyze the relationship between these three populations using inter simple sequence repeat DNA fingerprinting. Dose–response trials confirmed that the three populations were susceptible to glyphosate but resistant to nicosulfuron-methyl. Resistance to ALS inhibitors was due to several amino acid substitutions in positions Pro197, Trp574 and Ser653. Moreover, the substitutions Ser653Ile and Pro197Thr are described for the first time in this species. At field-labeled rates, all populations were fully controlled with alternative herbicides with other sites of action. Amaranthus palmeri individuals were clustered in three groups based on unweighted pair group method with arithmetic mean analysis, which corresponded to the three sampled populations, with a 67% of genetic relationship among them. Considering this high genetic variability and the different positions and amino acid substations found between populations, it was hypothesized that different colonization events occurred from the American continent probably prior to the introduction of glyphosate resistant crops. Prevention from new introductions is warranted because new herbicide resistance traits could arrive, complicating the management of this invasive weed species, while managing or eradicating the already established populations.}, number={7}, journal={Agronomy}, publisher={MDPI AG}, author={Torra, Joel and Royo-Esnal, Aritz and Romano, Yolanda and Osuna, María and León, Ramón and Recasens, Jordi}, year={2020}, month={Jul}, pages={993} }
 @article{reyes-cabrera_erickson_leon_quadros_silveira_sollenberger_2020, title={Bahiagrass pasture and elephantgrass bioenergy cropping systems differ in root traits}, volume={112}, ISSN={["1435-0645"]}, url={https://doi.org/10.1002/agj2.20382}, DOI={10.1002/agj2.20382}, abstractNote={AbstractRoot morphology and production are important for soil nutrient acquisition and C sequestration, but these traits are poorly understood in the bioenergy crop elephantgrass [Pennisetum purpureum (L.) Schum.]. Our objective was to characterize root traits of elephantgrass receiving different nutrient management practices in comparison with bahiagrass (Paspalum notatum Flüggé) pasture grown in the southeastern U.S. Treatments were bahiagrass + 50 kg N ha−1 (BHG), and elephantgrass receiving either: 50 kg N ha−1 (E50), 50 kg N ha−1 + biochar (E50BC), 50 kg N ha−1 + lignocellulosic fermentation residual (E50FR), or 250 kg N ha−1 (E250). Roots were sampled annually for 4 yr (2013‐2016). Root C and N concentration were measured at termination (2016) of the study. Both crop species exhibited similar root length density (RLD) and root mass density (RMD) across all depths in 2014 and 2015. BHG root diameter was 55% greater than all elephantgrass treatments. By 2016, E50FR increased elephantgrass RLD and RMD in the shallow soil layers (< 0.2 m). Root N content was 15–39% lower for all elephantgrass treatments than BHG in the 0‐0.1 m depth, and 22–25% lower for E50 and E50BC in the 0.1‐ to 0.2‐m depth compared with BHG. Additionally, roots C content was 6% higher in the 0‐0.1 m compared with the 0.1‐ to 0.2‐m soil depth irrespective of treatment. Application of biochar and lignocellulosic fermentation residual as amendments produced a stimulatory effect on elephantgrass root growth in soil shallow layers, which could affect nutrient and water acquisition.}, number={6}, journal={AGRONOMY JOURNAL}, publisher={Wiley}, author={Reyes-Cabrera, Joel and Erickson, John E. and Leon, Ramon G. and Quadros, Danilo G. and Silveira, Maria L. and Sollenberger, Lynn E.}, year={2020}, pages={4810–4821} }
 @article{kumar_seepaul_mulvaney_colvin_george_marois_bennett_leon_wright_small_2020, title={Brassica carinata genotypes demonstrate potential as a winter biofuel crop in South East United States}, volume={150}, url={https://doi.org/10.1016/j.indcrop.2020.112353}, DOI={10.1016/j.indcrop.2020.112353}, abstractNote={Brassica carinata A. Braun, grown as a winter crop on underutilized agricultural land in the southeast United States (SE US), may provide a new rotation alternative and augment income for producers. Widespread adoption of Brassica carinata as a winter crop in the SE US requires varieties with cold tolerance, acceptable and stable seed yield, oil content, protein content so that the crop will be complementary with the normal cultivation of summer crops such as cotton (Gossypium hirsutum L.), corn (Zea mays L.), soybean (Glycine max L. Merr), sorghum (Sorghum bicolor L. Moench) and peanut (Arachis hypogaea L.). The objective of this study was to evaluate the performance of 11 Brassica carinata genotypes for agronomically important traits including seed yield, oil and protein content, oil quality, days to bolting, flowering and maturity at three locations during two growing seasons (2015–2017) as a winter crop in the SE US. Interactions between genotype and environment played a crucial role in overall agronomic performance. This study provides key information on the effect of environmental conditions, such as precipitation and temperature on the agronomic performance of carinata along with generation of information related to region-specific requirements for the crop in the SE US. Days to maturity ranged from 154 to 165 days. The average yield of the 11 genotypes tested ranged from 2814 kg/ha to 3401 kg/ha, which were improved from earlier studies, demonstrating gain due to regional selection and breeding efforts. Total oil content ranged from 42.0 % to 52.4 %, while the erucic acid (C22:1) content ranged from 40.7 % to 42.9 % on a whole seed basis. Based on these results, specific genotypes with consistently high seed yield, oil, erucic acid and protein content with shorter life cycle irrespective of location or year were identified. Brassica carinata has potential as a viable bioenergy winter crop to be integrated into the cropping systems in the SE US and other regions of the world.}, journal={Industrial Crops and Products}, publisher={Elsevier BV}, author={Kumar, Shivendra and Seepaul, Ramdeo and Mulvaney, Michael J. and Colvin, Blaire and George, Sheeja and Marois, Jim J. and Bennett, Rick and Leon, Ramon and Wright, David L. and Small, Ian M.}, year={2020}, month={Aug}, pages={112353} }
 @article{piskackova_reberg-horton_richardson_austin_jennings_leon_2020, title={Creating Predictive Weed Emergence Models Using Repeat Photography and Image Analysis}, volume={9}, url={https://doi.org/10.3390/plants9050635}, DOI={10.3390/plants9050635}, abstractNote={Weed emergence models have the potential to be important tools for automating weed control actions; however, producing the necessary data (e.g., seedling counts) is time consuming and tedious. If similar weed emergence models could be created by deriving emergence data from images rather than physical counts, the amount of generated data could be increased to create more robust models. In this research, repeat RGB images taken throughout the emergence period of Raphanus raphanistrum L. and Senna obtusifolia (L.) Irwin and Barneby underwent pixel-based spectral classification. Relative cumulative pixels generated by the weed of interest over time were used to model emergence patterns. The models that were derived from cumulative pixel data were validated with the relative emergence of true seedling counts. The cumulative pixel model for R. raphanistrum and S. obtusifolia accounted for 92% of the variation in relative emergence of true counts. The results demonstrate that a simple image analysis approach based on time-dependent changes in weed cover can be used to generate weed emergence predictive models equivalent to those produced based on seedling counts. This process will help researchers working on weed emergence models, providing a new low-cost and technologically simple tool for data collection.}, number={5}, journal={Plants}, publisher={MDPI AG}, author={Piskackova, Theresa Reinhardt and Reberg-Horton, Chris and Richardson, Robert J and Austin, Robert and Jennings, Katie M and Leon, Ramon G}, year={2020}, month={May}, pages={635} }
 @article{shergill_schwartz‐lazaro_leon_ackroyd_flessner_bagavathiannan_everman_norsworthy_vangessel_mirsky_2020, title={Current outlook and future research needs for harvest weed seed control in North American cropping systems}, url={https://doi.org/10.1002/ps.5986}, DOI={10.1002/ps.5986}, abstractNote={AbstractHarvest weed seed control (HWSC) comprises a set of tools and tactics that prevents the addition of weed seed to the soil seed bank, attenuating weed infestations and providing a method to combat the development and spread of herbicide‐resistant weed populations. Initial HWSC research efforts in North America are summarized and, combined with the vast area of crops suitable for HWSC, clearly indicate strong potential for this technology. However, potential limitations exist that are not present in Australian cropping systems where HWSC was developed. These include rotations with crops that are not currently amenable to HWSC (e.g. corn), high moisture content at harvest, untimely harvest, and others. Concerns about weeds becoming resistant to HWSC (i.e. adapting) exist, as do shifts in weed species composition, particularly with the diversity of weeds in North America. Currently the potential of HWSC vastly outweighs any drawbacks, necessitating further research. Such expanded efforts should foremost include chaff lining and impact mill commercial scale evaluation, as this will address potential limitations as well as economics. Growers must be integrated into large‐scale, on‐farm research and development activities aimed at alleviating the problems of using HWSC systems in North America and drive greater adoption subsequently. © 2020 Society of Chemical Industry}, journal={Pest Management Science}, author={Shergill, Lovreet S and Schwartz‐Lazaro, Lauren M and Leon, Ramon and Ackroyd, Victoria J and Flessner, Michael L and Bagavathiannan, Muthukumar and Everman, Wesley and Norsworthy, Jason K and VanGessel, Mark J and Mirsky, Steven B}, year={2020}, month={Dec} }
 @article{tiwari_piskáčková_devkota_mulvaney_ferrell_leon_2021, title={Growing winter Brassica carinata as part of a diversified crop rotation for integrated weed management}, url={https://doi.org/10.1111/gcbb.12799}, DOI={10.1111/gcbb.12799}, abstractNote={AbstractBrassica carinata A. Braun is a non‐edible, oilseed winter crop for biofuel production that can diversify crop rotations and improve integrated weed management. The research objective was to evaluate the influence of B. carinata on weed population dynamics in the southeastern United States cropping systems. B. carinata was grown after cotton (Gossypium hirsutum L.), peanut (Arachis hypogea L.), or a clean summer fallow, and winter weed pressure was modified with or without S‐metolachlor. The emergence of Lamium amplexicaule L. increased at least 40% after cotton or peanut in 2018–2019 and 50% after cotton in 2019–2020 compared to summer fallow. Stellaria media (L.) Vill. emergence was increased over threefold after peanut or cotton in 2019–2020. Senna obtusifolia (L.) H.S. Irwin & Barneby emergence after cotton was increased at least 43% during both experimental years, whereas Amaranthus hybridus L. emergence was increased over 50% after peanut in 2019–2020 compared to summer fallow. Even without S‐metolachlor, B. carinata reduced A. hybridus (>27%) and S. obtusifolia (>25%) emergence compared to weedy winter fallow. After B. carinata harvest, A. hybridus emergence was reduced >40% with or without S‐metolachlor compared to winter fallow in 2018–2019. Overall, B. carinata biomass was highest after peanut for both seasons. B. carinata seed yield did not differ among crop history treatments in the first season, whereas in 2019–2020, the yield was higher after peanut (2417 kg ha−1) or fallow (2520 kg ha−1) compared to cotton (1710 kg ha−1). Weed management treatments were not different for B. carinata biomass or yield in any year. The results indicate that B. carinata can enhance integrated weed management strategies at the rotational level for summer crops by reducing seed banks of summer weed species, in addition to its potential as a winter biofuel crop for the southeastern United States.}, journal={GCB Bioenergy}, author={Tiwari, Ruby and Piskáčková, Theresa A. Reinhardt and Devkota, Pratap and Mulvaney, Michael J. and Ferrell, Jason A. and Leon, Ramon G.}, year={2021}, month={Mar} }
 @article{moore_jennings_monks_boyette_jordan_leon_2021, title={Herbicide systems including linuron for Palmer amaranth (Amaranthus palmeri) control in sweetpotato}, volume={35}, ISSN={["1550-2740"]}, DOI={10.1017/wet.2020.63}, abstractNote={AbstractField studies were conducted to determine sweetpotato tolerance to and weed control from management systems that included linuron. Treatments included flumioxazin preplant (107 g ai ha−1) followed by (fb) S-metolachlor (800 g ai ha−1), oryzalin (840 g ai ha−1), or linuron (280, 420, 560, 700, and 840 g ai ha−1) alone or mixed with S-metolachlor or oryzalin applied 7 d after transplanting. Weeds did not emerge before the treatment applications. Two of the four field studies were maintained weed-free throughout the season to evaluate sweetpotato tolerance without weed interference. The herbicide program with the greatest sweetpotato yield was flumioxazin fb S-metolachlor. Mixing linuron with S-metolachlor did not improve Palmer amaranth management and decreased marketable yield by up to 28% compared with flumioxazin fb S-metolachlor. Thus, linuron should not be applied POST in sweetpotato if Palmer amaranth has not emerged at the time of application.}, number={1}, journal={WEED TECHNOLOGY}, author={Moore, Levi D. and Jennings, Katherine M. and Monks, David W. and Boyette, Michael D. and Jordan, David L. and Leon, Ramon G.}, year={2021}, month={Feb}, pages={49–56} }
 @article{piskackova_reberg-horton_richardson_jennings_leon_2020, title={Incorporating environmental factors to describe wild radish (Raphanus raphanistrum) seedling emergence and plant phenology}, volume={68}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2020.64}, DOI={10.1017/wsc.2020.64}, abstractNote={AbstractWild radish (Raphanus raphanistrum L.) is a weed found globally in agricultural systems. The facultative winter annual nature of this plant and high genetic variability makes modeling its growth and phenology difficult. In the present study, R. raphanistrum natural seedbanks exhibited a biphasic pattern of emergence, with emergence peaks occurring in both fall and spring. Traditional sigmoidal models were inadequate to fit this pattern, regardless of the predictive environmental variable, and a corresponding biphasic model (sigmoidal + Weibull) was used to describe emergence based on the best parameters. Each best-fit chronological, thermal, and hydrothermal model accounted for at least 85% of the variation of the validation data. Observations on phenology progression from four cohorts were used to create a common model that described all cohorts adequately. Different phenological stages were described using chronological, thermal, hydrothermal, daylength-dependent thermal time, and daylength-dependent hydrothermal time. Integrating daylength and temperature into the models was important for predicting reproductive stages of R. raphanistrum.}, number={6}, journal={WEED SCIENCE}, publisher={Cambridge University Press (CUP)}, author={Piskackova, Theresa Reinhardt and Reberg-Horton, S. Chris and Richardson, Robert J. and Jennings, Katie M. and Leon, Ramon G.}, year={2020}, month={Nov}, pages={627–638} }
 @article{hare_jordan_leon_edmisten_post_cahoon_everman_mahoney_inman_2020, title={Influence of timing and intensity of weed management on crop yield and contribution to weed emergence in cotton the following year}, volume={6}, ISSN={["2374-3832"]}, url={https://doi.org/10.1002/cft2.20021}, DOI={10.1002/cft2.20021}, abstractNote={AbstractAdequate weed control is important in protecting crop yield and allowing efficient harvest in North Carolina. Data in the literature are limited with respect to direct comparisons of weed control and yield across multiple crops. Research is also limited in terms of documenting the impact of weed control in one crop on weed populations in the crop planted the following season. Experiments were conducted in North Carolina to determine weed control and yield of corn (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean [Glycine max (L.) Merr.] in the same experiment when herbicides were applied postemergence at different timings (Year 1) and to determine how weed control translated into weed populations and cotton yield the following year (Year 2). Herbicides were applied 2 or 6 wk after planting (WAP); 2 and 4 WAP; 4 and 6 WAP; and 2, 4, and 6 WAP. At Lewiston‐Woodville, common ragweed (Ambrosia artemisiifolia L.) and Texas millet (Urochloa texana L.) were present. At Rocky Mount, Palmer amaranth (Amanthus palmeri S. Wats) and large crabgrass (Digitaria sanguinalis L.) were present. A single postemergence application of herbicide protected yield from weed interference in corn, whereas in most instances multiple herbicide applications were needed in cotton and to a degree in soybean. Weed densities in Year 2 in cotton were negatively correlated with weed control the previous year in corn, cotton, and soybean. Densities of common ragweed and Palmer amaranth 3 WAP in Year 2 were higher in cotton when the preceding crop was cotton or soybean rather than corn when herbicides were not applied; no difference was noted when comparing cotton and soybean. In some instances, sequential applications of herbicides resulted in lower weed densities the following year in cotton. These results demonstrate the importance of timely, sequential herbicide applications for weed control in cotton and soybean and in some instances the positive benefits on weed populations the following year in cotton.}, number={1}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, publisher={Wiley}, author={Hare, Andrew T. and Jordan, David L. and Leon, Ramon G. and Edmisten, Keith L. and Post, Angela R. and Cahoon, Charles W. and Everman, Wesley J. and Mahoney, Denis J. and Inman, Matthew D.}, year={2020} }
 @article{piskackova_reberg-horton_richardson_jennings_leon_2020, title={Integrating emergence and phenology models to determine windows of action for weed control: A case study using Senna obtusifolia}, volume={258}, ISSN={["1872-6852"]}, DOI={10.1016/j.fcr.2020.107959}, abstractNote={The success of integrated weed management strategies is contingent on the accuracy of control actions in both time and space. While emphasis has been given to spatial accuracy, timing accuracy has been largely neglected. Weed control timing must consider not only the total duration of weed interference with the crop, as done by the traditional critical period of weed control (CPWC) based on yield protection only, but also weed growth, size, and susceptible phenological stages. In this study, we expand upon the idea of using weed emergence models for timing weed control by integrating them with phenology probability models for key weed growth stages to optimize timing of control actions, here referred as Critical Control Windows (CCW). Combining the CCW with thresholds for yield loss due to weed interference and thresholds for weed survival risk makes it possible determining the frequency with which control actions should be implemented to maintain crop yield and weed populations at desired levels. Using Senna obtusifolia as a study case, vegetative and reproductive phenological stages were modeled as a function of seedling emergence for different cohorts. Chronological and thermal-time models provided robust predictions of S. obtusifolia phenology. CCW did not always coincided with CPWC for several crops when considering 10-cm tall plants as the threshold for control. In general, for summer row crops, CCW required 2 postemergence control actions and sometimes 1 action outside the CPWC. The results of the present research illustrate how predictive models can be used to develop CCW that will complement the traditional CPWC. These two concepts when used complementary can increase not only timing accuracy, but also efficiency of weed control.}, journal={FIELD CROPS RESEARCH}, author={Piskackova, Theresa A. Reinhardt and Reberg-Horton, Chris and Richardson, Robert J. and Jennings, Katie M. and Leon, Ramon G.}, year={2020}, month={Nov} }
 @article{jani_mulvaney_erickson_leon_wood_rowland_enloe_2020, title={Peanut nitrogen credits to winter wheat are negligible under conservation tillage management in the southeastern USA}, volume={249}, ISSN={["1872-6852"]}, DOI={10.1016/j.fcr.2020.107739}, abstractNote={Agricultural extension services in many peanut (Arachis hypogaea L.)-producing regions recommend that farmers reduce nitrogen (N) fertilization rates, or apply N credits, to crops planted after peanut but do not typically specify how peanut residue management or planting schedules of subsequent crops affect the magnitude of peanut N credits. The objective of this study was to quantify peanut N credits to winter wheat (Triticum aestivum L.) in a conservation tillage cropping system in different subtropical growing environments. A five site-year study was conducted in Florida, USA beginning in 2016. A split-plot experimental design was arranged in which summer crop [peanut, cotton (Gossypium hirsutum L.), and weed-free fallow] was the main plot factor, while N rate (0, 34, 67, and 101 kg N ha−1) to winter wheat was the split plot factor. Peanut and cotton were planted under strip-tillage, while winter wheat was drilled into peanut and cotton residues and weed-free fallow plots without tillage. Although peanut residues accumulated 54–93 kg N ha−1, plant available N at winter wheat planting in the 0–15 cm soil depth range of former peanut plots was only higher than in former cotton or fallow plots for one site-year. A previous peanut crop did not affect winter wheat grain yield, but there were cases of lower grain yield, grain N removal, and agronomic efficiency following cotton relative to peanut depending on site. Nonlinear regression procedures predicted that N rates required to optimize grain yields following peanut would exceed 94 kg N ha−1, further indicating the absence of detectible peanut N credits in this study. These results suggest that assuming peanut provides N credits to subsequent crops in the southeastern USA is not justified and, if assumed, will reduce the productivity of subsequent crops.}, journal={FIELD CROPS RESEARCH}, author={Jani, Arun D. and Mulvaney, Michael J. and Erickson, John E. and Leon, Ramon G. and Wood, C. Wesley and Rowland, Diane L. and Enloe, Heather A.}, year={2020}, month={Apr} }
 @article{hare_jordan_edmisten_leon_post_vann_dunphy_heiniger_collins_washburn_2020, title={Response of agronomic crops to planting date and double-cropping with wheat}, volume={112}, ISSN={["1435-0645"]}, url={https://doi.org/10.1002/agj2.20164}, DOI={10.1002/agj2.20164}, abstractNote={AbstractPlanting date can affect crop yield and is an important management decision for practitioners. Although wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] can be effectively double‐cropped in North Carolina, if commodity prices and projected economic returns are higher for crops other than soybean, growers might consider a nontraditional, double‐crop system. Direct comparisons of major agronomic crops with different planting dates or in a double‐crop system with wheat are limited in North Carolina. Therefore, research was conducted in North Carolina from 2013 through 2017 to determine yield potential of corn (Zea mays L.), cotton (Gossypium hirsutum L.), grain sorghum [Sorghum bicolor (L.) Moench], peanut (Arachis hypogaea L.), and soybean planted at two dates within the recommended planting window for full‐season production versus planting these crops after wheat harvest. The experimental design was a split plot, with summer crop serving as the whole plot unit and planting date within a crop serving as the subplot unit. Yield of corn, cotton, grain sorghum, peanut, and soybean in full‐season production exceeded that of double‐cropping with wheat in 5, 5, 2, 4, and 5 yr out of 5 yr of the study, respectively. Estimated economic returns were generated using the 10‐yr average (2008–2017) summer crop prices with the 10‐yr average wheat price. When considering all possible combinations of years and crops (n = 25), in only 20% of the possible combinations was the economic return of the double‐cropping system greater than economic return of full‐season crop production when compared with at least one of the planting dates within the traditional planting window.}, number={3}, journal={AGRONOMY JOURNAL}, publisher={Wiley}, author={Hare, Andrew T. and Jordan, David L. and Edmisten, Keith L. and Leon, Ramon G. and Post, Angela R. and Vann, Rachel and Dunphy, E. James and Heiniger, Ronnie and Collins, Guy and Washburn, Derek}, year={2020}, pages={1972–1980} }
 @article{silveira_brandani_kohmann_erickson_reyes-cabrera_leon_sollenberger_piotto_quadros_mello_2020, title={Short-term effects of bioenergy cropping on soil carbon and nitrogen dynamics in a Florida Ultisol}, volume={84}, ISSN={["1435-0661"]}, DOI={10.1002/saj2.20081}, abstractNote={AbstractAlthough perennial bioenergy crops provide a potential for soil C sequestration, high fertilizer inputs are required to sustain yields. Land application of bioenergy byproducts can be an effective strategy to reduce the use of inorganic fertilizer. This study examined the impacts of elephantgrass [Pennisetum purpureum (L.) Schum.] bioenergy cropping and conventional pasture on soil C and N responses. Treatments included (a) bahiagrass + 50 kg N ha−1 yr−1 (BHG), (b) elephantgrass + 50 kg N ha−1 yr−1 (E50), (c) elephantgrass + 50 kg N ha−1 yr−1 + fermentation residual (E50FR), (d) elephantgrass + 50 kg N ha−1 yr−1 + biochar (E50BC), and (e) elephantgrass + 250 kg N ha−1 yr−1 (E250). Soil C and N responses occurred mainly at the 0‐ to 10‐cm depth. Biochar resulted in the largest increase in soil C stocks at the 0‐ to 10‐cm depth (5.8 Mg C ha−1 in 2012 vs. 40 Mg C ha−1 in 2016), but no differences were observed among the other treatments. Conversely, greater soil N stocks at the 0‐ to 10‐cm depth were associated with the BHG (0.8 and 0.34 Mg N ha−1 for other treatments). Biochar favored N and C accumulation in the mineral‐associated (<53 μm) fraction, possibly from the accumulation of fine biochar fragments. In contrast, fermentation residual promoted C accumulation in unprotected light fraction. These results are supported by the δ13C signature and C/N ratios of the fractions. Results underscore the value of recycling biochar in bioenergy cropping systems as a means of improving C in coarse‐textured soils.}, number={4}, journal={SOIL SCIENCE SOCIETY OF AMERICA JOURNAL}, author={Silveira, M. L. and Brandani, C. B. and Kohmann, M. M. and Erickson, J. E. and Reyes-Cabrera, J. and Leon, R. G. and Sollenberger, L. E. and Piotto, V. and Quadros, D. G. and Mello, S. Q. S.}, year={2020}, pages={1233–1246} }
 @article{bagavathiannan_beckie_chantre_gonzalez-andujar_leon_neve_poggio_schutte_somerville_werle_et al._2020, title={Simulation Models on the Ecology and Management of Arable Weeds: Structure, Quantitative Insights, and Applications}, volume={10}, url={https://doi.org/10.3390/agronomy10101611}, DOI={10.3390/agronomy10101611}, abstractNote={In weed science and management, models are important and can be used to better understand what has occurred in management scenarios, to predict what will happen and to evaluate the outcomes of control methods. To-date, perspectives on and the understanding of weed models have been disjointed, especially in terms of how they have been applied to advance weed science and management. This paper presents a general overview of the nature and application of a full range of simulation models on the ecology, biology, and management of arable weeds, and how they have been used to provide insights and directions for decision making when long-term weed population trajectories are impractical to be determined using field experimentation. While research on weed biology and ecology has gained momentum over the past four decades, especially for species with high risk for herbicide resistance evolution, knowledge gaps still exist for several life cycle parameters for many agriculturally important weed species. More research efforts should be invested in filling these knowledge gaps, which will lead to better models and ultimately better inform weed management decision making.}, number={10}, journal={Agronomy}, publisher={MDPI AG}, author={Bagavathiannan, Muthukumar V. and Beckie, Hugh J. and Chantre, Guillermo R. and Gonzalez-Andujar, Jose L. and Leon, Ramon G. and Neve, Paul and Poggio, Santiago L. and Schutte, Brian J. and Somerville, Gayle J. and Werle, Rodrigo and et al.}, year={2020}, month={Oct}, pages={1611} }
 @article{mahoney_jordan_roma-burgos_jennings_leon_vann_everman_cahoon_2020, title={Susceptibility of Palmer amaranth (Amaranthus palmeri) to herbicides in accessions collected from the North Carolina Coastal Plain}, volume={68}, ISSN={["1550-2759"]}, url={http://dx.doi.org/10.1017/wsc.2020.67}, DOI={10.1017/wsc.2020.67}, abstractNote={AbstractPalmer amaranth (Amaranthus palmeri S. Watson) populations resistant to acetolactate synthase (ALS)-inhibiting herbicides and glyphosate are fairly common throughout the state of North Carolina (NC). This has led farm managers to rely more heavily on herbicides with other sites of action (SOA) for A. palmeri control, especially protoporphyrinogen oxidase and glutamine synthetase inhibitors. In the fall of 2016, seeds from A. palmeri populations were collected from the NC Coastal Plain, the state’s most prominent agricultural region. In separate experiments, plants with 2 to 4 leaves from the 110 populations were treated with field use rates of glyphosate, glufosinate-ammonium, fomesafen, mesotrione, or thifensulfuron-methyl. Percent visible control and survival were evaluated 3 wk after treatment. Survival frequencies were highest following glyphosate (99%) or thifensulfuron-methyl (96%) treatment. Known mutations conferring resistance to ALS inhibitors were found in populations surviving thifensulfuron-methyl application (Ala-122-Ser, Pro-197-Ser, Trp-574-Leu, and/or Ser-653-Asn), in addition to a new mutation (Ala-282-Asp) that requires further investigation. Forty-two populations had survivors after mesotrione application, with one population having 17% survival. Four populations survived fomesafen treatment, while none survived glufosinate. Dose–response studies showed an increase in fomesafen needed to kill 50% of two populations (LD50); however, these rates were far below the field use rate (less than 5 g ha−1). In two populations following mesotrione dose–response studies, a 2.4- to 3.3-fold increase was noted, with LD90 values approaching the field use rate (72.8 and 89.8 g ha−1). Screening of the progeny of individuals surviving mesotrione confirmed the presence of resistance alleles, as there were a higher number of survivors at the 1X rate compared with the parent population, confirming resistance to mesotrione. These data suggest A. palmeri resistant to chemistries other than glyphosate and thifensulfuron-methyl are present in NC, which highlights the need for weed management approaches to mitigate the evolution and spread of herbicide-resistant populations.}, number={6}, journal={WEED SCIENCE}, publisher={Cambridge University Press (CUP)}, author={Mahoney, Denis J. and Jordan, David L. and Roma-Burgos, Nilda and Jennings, Katherine M. and Leon, Ramon G. and Vann, Matthew C. and Everman, Wesley J. and Cahoon, Charles W.}, year={2020}, month={Nov}, pages={582–593} }
 @article{mahoney_jordan_hare_roma-burgos_jennings_leon_vann_everman_cahoon_2021, title={The influence of soybean population and POST herbicide application timing on in-season and subsequent-season Palmer amaranth (Amaranthus palmeri) control and economic returns}, volume={35}, ISSN={["1550-2740"]}, DOI={10.1017/wet.2020.87}, abstractNote={AbstractOverreliance on herbicides for weed control has led to the evolution of herbicide-resistant Palmer amaranth populations. Farm managers should consider the long-term consequences of their short-term management decisions, especially when considering the soil weed seedbank. The objectives of this research were to (1) determine how soybean population and POST herbicide application timing affects in-season Palmer amaranth control and soybean yield, and (2) how those variables influence Palmer amaranth densities and cotton yields the following season. Soybeans were planted (19-cm row spacing) at a low-, medium-, and high-density population (268,000, 546,000, and 778,000 plants ha–1, respectively). Fomesafen and clethodim (280 and 210 g ai ha–1, respectively) were applied at the VE, V1, or V2 to V3 soybean growth stage. Nontreated plots were also included to assess the effect of soybean population alone. The following season, cotton was planted into these plots so as to understand the effects of soybean planting population on Palmer amaranth densities in the subsequent crop. When an herbicide application occurred at the V1 or V2 to V3 soybean stage, weed control in the high-density soybean population increased 17% to 23% compared to the low-density population. Economic return was not influenced by soybean population and was increased 72% to 94% with herbicide application compared to no treatment. In the subsequent cotton crop, Palmer amaranth densities were 24% to 39% lower 3 wk after planting when following soybean sprayed with herbicides compared to soybean without herbicides. Additionally, Palmer amaranth densities in cotton were 19% lower when soybean was treated at the VE stage compared to later stages. Thus, increasing soybean population can improve Palmer amaranth control without adversely affecting economic returns and can reduce future weed densities. Reducing the weed seedbank and selection pressure from herbicides are critical in mitigating resistance evolution.}, number={1}, journal={WEED TECHNOLOGY}, author={Mahoney, Denis J. and Jordan, David L. and Hare, Andrew T. and Roma-Burgos, Nilda and Jennings, Katherine M. and Leon, Ramon G. and Vann, Matthew C. and Everman, Wesley J. and Cahoon, Charles W.}, year={2021}, month={Feb}, pages={106–112} }
 @article{leon_dunne_gould_2021, title={The role of population and quantitative genetics and modern sequencing technologies to understand evolved herbicide resistance and weed fitness}, url={https://doi.org/10.1002/ps.5988}, DOI={10.1002/ps.5988}, abstractNote={AbstractEvolution of resistance to multiple herbicides with different sites of action and of nontarget site resistance (NTSR) often involves multiple genes. Thus, single‐gene analyses, typical in studies of target site resistance, are not sufficient for understanding the genetic architecture and dynamics of NTSR and multiple resistance. The genetics of weed adaptation to varied agricultural environments is also generally expected to be polygenic. Recent advances in whole‐genome sequencing as well as bioinformatic and statistical tools have made it possible to use population and quantitative genetics methods to expand our understanding of how resistance and other traits important for weed adaptation are genetically controlled at the individual and population levels, and to predict responses to selection pressure by herbicides and other environmental factors. The use of tools such as quantitative trait loci mapping, genome‐wide association studies, and genomic prediction will allow pest management scientists to better explain how pests adapt to control tools and how specific genotypes thrive and spread across agroecosystems and other human‐disturbed systems. The challenge will be to use this knowledge in developing integrated weed management systems that inhibit broad resistance to current and future weed‐control methods. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.}, journal={Pest Management Science}, author={Leon, Ramon G and Dunne, Jeffrey C and Gould, Fred}, year={2021}, month={Jan} }
 @article{martin_dias_sellers_ferrell_leon_vendramini_2020, title={Tolerance of pintoi peanut to PRE and POST herbicides}, volume={34}, ISSN={["1550-2740"]}, DOI={10.1017/wet.2020.82}, abstractNote={AbstractPintoi peanut is a warm-season perennial legume that shows promise as a forage crop for the southeastern United States, however, little is known about the proper methods of weed management during establishment for this species. The objective of this study was to determine the ability of pintoi peanut to tolerate applications of PRE and POST herbicides during the year of and year after planting. The effects of herbicide treatments on percentage of visual estimates of injury and stand counts of pintoi peanut were investigated at Ona and Marianna, FL, in 2015 and 2016. All PRE herbicides did not result in significant injury or stand reduction. Pintoi peanut’s tolerance to POST herbicides was higher when plants were emerged for at least 2 wk prior to herbicide application. Stands of pintoi peanut that were planted the previous year appear to tolerate all herbicides examined in this work, except sulfosulfuron. Results of this study indicate that at the year of planting pintoi peanut is tolerant to PRE applications of pendimethalin, imazethapyr, and imazapic. Pintoi peanut appears to tolerate applications of 2,4-D, carfentrazone, imazapic and imazethapyr the year after planting at the rates utilized in this study. Future research should evaluate the effects of multiple herbicide applications and tank-mixes to obtain satisfactory weed control and selectivity in pintoi peanut swards.}, number={6}, journal={WEED TECHNOLOGY}, author={Martin, Logan J. and Dias, Jose Luiz C. S. and Sellers, Brent A. and Ferrell, Jason A. and Leon, Ramon G. and Vendramini, Joao M. B.}, year={2020}, month={Dec}, pages={870–875} }
 @article{martin_sellers_devkota_ferrell_leon_vendramini_2021, title={Tolerance of rhizoma perennial peanut to glyphosate and triclopyr}, volume={35}, ISSN={["1550-2740"]}, url={https://doi.org/10.1017/wet.2020.126}, DOI={10.1017/wet.2020.126}, abstractNote={AbstractRhizoma perennial peanut (RPP) is well adapted to the Gulf Coast region of the United States, but its varietal tolerance to glyphosate and triclopyr is not well defined. The research was conducted to determine the effect of various rates of glyphosate and triclopyr on established RPP, and the response of common RPP varieties to these herbicides. The RPP sward was approximately 7 yr younger at Zolfo Springs than at the Ona location. RPP showed moderate tolerance to glyphosate and triclopyr application, and injury level did not differ with the age of RPP sward. However, biomass production was negatively influenced by the age of the RPP sward. Overall, injury from glyphosate applications did not exceed 40% at either site. The glyphosate rate for 20% biomass reduction was predicted to be 0.53 and 2.17 kg ae ha−1at Zolfo Springs and Ona, respectively. RPP injury from triclopyr was greater at the Zolfo Springs location than at Ona, and the triclopyr rate predicted to result in a 20% biomass reduction was 0.45 and 0.99 kg ae ha−1at the Zolfo Springs and Ona locations, respectively. There was a difference on RPP varieties response to glyphosate and triclopyr application. ‘Florigraze’ and ‘Ona 33’ were less tolerant to glyphosate compared to ‘UF-Tito’ and ‘Ecoturf’ at 30 d after treatment. Likewise, UF-Tito and Florigraze were less tolerant to triclopyr compared to Ona 33 and Ecoturf. Overall, Florigraze showed highest injury and at least 2-fold reduction on biomass compared to the other three varieties from glyphosate or triclopyr application. Results from this research indicate that glyphosate and triclopyr appear to be safe to apply to long-established RPP stands, but herbicide rate and RPP varieties should be considered if stands are <5 yr old.}, number={4}, journal={WEED TECHNOLOGY}, publisher={Cambridge University Press (CUP)}, author={Martin, Logan J. and Sellers, Brent A. and Devkota, Pratap and Ferrell, Jason A. and Leon, Ramon G. and Vendramini, Joao M. B.}, year={2021}, month={Aug}, pages={525–531} }
 @article{unruh_trenholm_harlow_leon_2020, title={Weed Management Guide for Florida Lawns}, url={https://doi.org/10.32473/edis-ep141-2019}, DOI={10.32473/edis-ep141-2019}, abstractNote={Weeds can be defined as unwanted plants or plants growing out of place. Proper identification and some understanding of how and why weeds are present in a lawn are important when selecting the best control strategy. Knowing if weeds were previously present in an area also helps homeowners prepare control measures in the future. Weed control should be a carefully planned and coordinated program.https://edis.ifas.ufl.edu/ep141
Previous version: Unruh, Joseph, Ramon Leon, Barry Brecke, and Laurie Trenholm. 2013. “Weed Management Guide for Florida Lawns”. EDIS 2013 (7). https://journals.flvc.org/edis/article/view/121086.}, journal={EDIS}, author={Unruh, J. Bryan and Trenholm, Laurie and Harlow, Erin and Leon, Ramon G.}, year={2020}, month={Sep} }
 @article{reyes-cabrera_erickson_leon_silveira_sollenberger_2019, title={Amending marginal sandy soils with biochar and lignocellulosic fermentation residual sustains fertility in elephantgrass bioenergy cropping systems}, volume={115}, ISSN={["1573-0867"]}, DOI={10.1007/s10705-019-10011-6}, number={1}, journal={NUTRIENT CYCLING IN AGROECOSYSTEMS}, author={Reyes-Cabrera, Joel and Erickson, John E. and Leon, Ramon G. and Silveira, Maria L. and Sollenberger, Lynn E.}, year={2019}, month={Sep}, pages={69–83} }
 @article{liu_unruh_kenworthy_macdonald_trenholm_leon_2019, title={Application Timing Affects Tolerance of Zoysiagrass to Fluazifop-P-butyl and Safening Effect of Triclopyr}, volume={59}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2018.12.0724}, abstractNote={ABSTRACTAryloxyphenoxypropionate (AOPP) herbicides, such as fluazifop‐P‐butyl, can be used for postemergence control of grassy weeds in zoysiagrass (Zoysia spp.), although the turf might suffer transient injury. This injury can be reduced by tank mixing fluazifop‐P‐butyl with triclopyr, an herbicide that behaves as a safener for AOPP herbicides. To characterize seasonal variation in zoysiagrass injury caused by fluazifop‐P‐butyl and triclopyr applications, we conducted a 2‐yr study on three Zoysia spp. cultivars (‘Empire’, ‘Geo’, and ‘Zeon’) at Jay, FL, from August 2015 to April 2017, evaluating how injury and turf quality were affected after spring, summer, and fall applications. The level of injury and changes in turf quality were influenced by fluazifop‐P‐butyl application timing, but the most sensitive season varied with the cultivar. The seasons with the greatest injury were also the ones in which the safening activity of triclopyr was most effective. In addition, when triclopyr was applied with fluazifop‐P‐butyl, the quality of all evaluated cultivars recovered to the level of nontreated controls by 2 wk after treatment. Nonstructural carbohydrate content was not affected by herbicide applications, but there were major differences in glucose and starch content between above‐ and belowground tissue depending on cultivar and season. Overall, our study confirmed that tank mixing triclopyr can reduce fluazifop‐P‐butyl phytotoxicity in zoysiagrass, and in the case of relatively tolerant cultivars, it might allow the use of rates higher than the current labeled rate with little negative impact on turf quality while providing better control of both broadleaf and grassy weeds.}, number={4}, journal={CROP SCIENCE}, author={Liu, Wenwen and Unruh, J. Bryan and Kenworthy, Kevin E. and MacDonald, Gregory E. and Trenholm, Laurie E. and Leon, Ramon G.}, year={2019}, pages={1789–1798} }
 @article{mulvaney_leon_seepaul_wright_hoffman_2019, title={Brassica carinata Seeding Rate and Row Spacing Effects on Morphology, Yield, and Oil}, volume={111}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2018.05.0316}, abstractNote={Core Ideas

Carinata growth and yield was influenced more by row spacing than seeding rate.
Rows spaced at 36 cm maximized carinata yield.
Carinata branching was favored by wider row spacing.
Carinata (Brassica carinata A. Braun) is an oilseed crop with potential as a winter crop in the southeastern United States to diversify crop rotations and provide biofuel production and livestock feed. The objective was to evaluate the effects of row spacing and seeding rate on carinata yield and oil composition. Field experiments were conducted in Jay and Quincy, FL, from 2013 to 2016 evaluating carinata growth, seed and oil yield, and oil composition grown in a factorial arrangement of four seeding rates (3, 6, 9, and 12 kg ha−1) and four row spacings (18, 36, 53, and 89 cm). No interactions between seeding rate and row spacing were detected. Seeding rate did not influence any of the variables studied. In contrast, row spacing affected seed and oil yield, branch production, and pods per plant. Seed yield (ranked from highest to lowest) was 2761, 2286, 1851, and 1572 kg ha−1 for rows spaced at 36, 18, 53, and 89 cm, respectively. Branching and pods per plant increased with row spacing. Neither seeding rate nor row spacing affected oil concentration and quality. Oil concentration averaged 40%, of which more than a third was erucic acid (C22:1). Protein concentration was 31%, and glucosinolate concentration was 93 μmol g−1. The results of the present study demonstrated that carinata can be successfully grown in the southeastern United States, reaching yields and oil quality similar to those reported at other latitudes, and can be a source of biofuel, protein for animal feed, and cropping system diversification for growers.}, number={2}, journal={AGRONOMY JOURNAL}, author={Mulvaney, Michael J. and Leon, Ramon G. and Seepaul, Ramdeo and Wright, David L. and Hoffman, Travis L.}, year={2019}, pages={528–535} }
 @article{price_li_leon_price_2020, title={Cotton response to preplant applications of 2,4-D or dicamba}, volume={34}, ISSN={["1550-2740"]}, DOI={10.1017/wet.2019.98}, abstractNote={AbstractSensitive cotton varieties planted into soil treated with 2,4-D or dicamba utilized in burndowns can result in stunting and stand loss if use rate is too high and the plant-back interval is too short. The objective of this study was to evaluate cotton stunting and yield responses resulting from 2,4-D or dicamba residues in soil after preplant burndown applications at three locations in 2016 and 2017. Treatments with 2,4-D included 532 and 1,063 g ae ha−1 applied 3 wk before planting (WBP) and 53, 160, 266, 532, 1,063 g ae ha−1 applied at planting. Dicamba treatments included 560 and 1,120 g ae h−1 applied 3 WBP and 56, 168, 280, 560, 1,120 g ae ha−1 applied at planting. Dicamba or 2,4-D treatments applied 3 WBP resulted in no adverse effects on cotton stand, plant height, or yield. Dicamba 560 g ae h−1 applied at planting reduced cotton stand by 36% at 21 to 24 d after planting (DAP) over all locations in 2016. In 2017, stands were reduced by dicamba at 168, 280, 560, and 1,120 g ae ha−1 by 17% to 25% at 20 to 23 DAP. Moreover, cotton stands were not affected by 2,4-D in 2016, and only 266, 532, and 1,063 g ae ha−1 of 2,4-D caused stand reductions of 26% to 36% at 20 to 23 DAP over all locations in 2017. Dicamba at 560 g ae ha−1 at planting was the only treatment in this study that reduced plant height. Although stand losses were observed in both years, no yield loss occurred. The data suggest that stunting and stand reduction may occur if susceptible varieties are planted soon after burndown applications with 2,4-D or dicamba, but yield may not be affected after a full growing season. Dicamba showed greater potential to cause stunting and stand reduction than 2,4-D.}, number={1}, journal={WEED TECHNOLOGY}, author={Price, Katilyn and Li, Xiao and Leon, Ramon G. and Price, Andrew}, year={2020}, month={Feb}, pages={96–100} }
 @article{hunter_gannon_richardson_yelverton_leon_2020, title={Coverage and drift potential associated with nozzle and speed selection for herbicide applications using an unmanned aerial sprayer}, volume={34}, url={https://doi.org/10.1017/wet.2019.101}, DOI={10.1017/wet.2019.101}, abstractNote={AbstractIn recent years, unmanned aerial vehicle (UAV) technology has expanded to include UAV sprayers capable of applying pesticides. Very little research has been conducted to optimize application parameters and measure the potential of off-target movement from UAV-based pesticide applications. Field experiments were conducted in Raleigh, NC during spring 2018 to characterize the effect of different application speeds and nozzle types on target area coverage and uniformity of UAV applications. The highest coverage was achieved with an application speed of 1 m s−1 and ranged from 30% to 60%, whereas applications at 7 m s−1 yielded 13% to 22% coverage. Coverage consistently decreased as application speed increased across all nozzles, with extended-range flat-spray nozzles declining at a faster rate than air-induction nozzles, likely due to higher drift. Experiments measuring the drift potential of UAV-applied pesticides using extended-range flat spray, air-induction flat-spray, turbo air–induction flat-spray, and hollow-cone nozzles under 0, 2, 4, 7, and 9 m s−1 perpendicular wind conditions in the immediate 1.75 m above the target were conducted in the absence of natural wind. Off-target movement was observed under all perpendicular wind conditions with all nozzles tested but was nondetectable beyond 5 m away from the target. Coverage from all nozzles exhibited a concave-shaped curve in response to the increasing perpendicular wind speed due to turbulence. The maximum target coverage in drift studies was observed when the perpendicular wind was 0 and 8.94 m s−1, but higher turbulence at the two highest perpendicular wind speeds (6.71 and 8.94 m s−1) increased coverage variability, whereas the lowest variability was observed at 2.24 m s−1 wind speed. Results suggested that air-induction flat-spray and turbo air–induction flat-spray nozzles and an application speed of 3 m s−1 provided an adequate coverage of target areas while minimizing off-target movement risk.}, number={2}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Hunter, Joseph E., III and Gannon, Travis W. and Richardson, Robert J. and Yelverton, Fred H. and Leon, Ramon G.}, year={2020}, month={Apr}, pages={235–240} }
 @article{jones_owen_leon_2019, title={Influence of multiple herbicide resistance on growth in Amaranthus tuberculatus}, volume={59}, ISSN={["1365-3180"]}, url={https://doi.org/10.1111/wre.12361}, DOI={10.1111/wre.12361}, abstractNote={SummaryPlant defence traits, such as herbicide resistance mutations, may incur a fitness cost to plants that become evident when the trait is not needed. However, individuals with multiple herbicide resistance traits may decrease fitness beyond that of plants with a single herbicide resistance mutation. Multiple herbicide‐resistant (MHR) Amaranthus tuberculatus populations are becoming more prevalent in Midwest United States agroecosystems. The objective was to determine whether selected MHR A. tuberculatus populations express differential development when grown in a herbicide‐free environment. The hypothesis was that MHR A. tuberculatus populations become increasingly less fit when additional herbicide resistances evolve. Multiple herbicide‐resistant and herbicide‐susceptible A. tuberculatus populations were grown in a herbicide‐free field for 20 weeks for two seasons. Differences (P < 0.001) in apical growth were detected 5 and 7 weeks after transplanting for all populations in 2016 and 2017 respectively. Gender and population influenced (P < 0.001) flowering date, with males flowering up to 1.5 weeks earlier than females, but did not cause pollination asynchrony. Shoot biomass was not different (P = 0.84) across A. tuberculatus populations, but there were differences (P < 0.001) for gender and year. Seed production was different amongst A. tuberculatus populations (P = 0.001), but was not influenced by the number of MHR traits. Conversely, a negative quadratic relationship between seed mass and the number of MHR traits was observed (r2 = 0.32; P < 0.001). The experiment results demonstrate that MHR in A. tuberculatus populations is not incurring a fitness penalty that will remove the populations in the immediate future.}, number={3}, journal={WEED RESEARCH}, publisher={Wiley}, author={Jones, E. A. L. and Owen, M. D. K. and Leon, R. G.}, editor={Darmency, HenriEditor}, year={2019}, month={Jun}, pages={235–244} }
 @article{hunter_gannon_richardson_yelverton_leon_2020, title={Integration of remote‐weed mapping and an autonomous spraying unmanned aerial vehicle for site‐specific weed management}, url={https://doi.org/10.1002/ps.5651}, DOI={10.1002/ps.5651}, abstractNote={AbstractBACKGROUNDUnmanned aerial vehicles (UAVs) have been used in agriculture to collect imagery for crop and pest monitoring, and for decision‐making purposes. Spraying‐capable UAVs are now commercially available worldwide for agricultural applications. Combining UAV weed mapping and UAV sprayers into an UAV integrated system (UAV‐IS) can offer a new alternative to implement site‐specific pest management.RESULTSThe UAV‐IS was 0.3‐ to 3‐fold more efficient at identifying and treating target weedy areas, while minimizing treatment on non‐weedy areas, than ground‐based broadcast applications. The UAV‐IS treated 20–60% less area than ground‐based broadcast applications, but also missed up to 26% of the target weedy area, while broadcast applications covered almost the entire experimental area and only missed 2–3% of the target weeds. The efficiency of UAV‐IS management practices increased as weed spatial aggregation increased (patchiness).CONCLUSIONIntegrating UAV imagery for pest mapping and UAV sprayers can provide a new strategy for integrated pest management programs to improve efficiency and efficacy while reducing the amount of pesticide being applied. The UAV‐IS has the potential to improve the detection and control of weed escapes to reduce/delay herbicide resistance evolution. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.}, journal={Pest Management Science}, author={Hunter, Joseph E, III and Gannon, Travis W and Richardson, Robert J and Yelverton, Fred H and Leon, Ramon G}, year={2020}, month={Apr} }
 @inbook{leon_jordan_bolfrey-arku_dzomeku_2019, edition={1}, title={Sustainable Weed Management in Peanut.}, booktitle={Weed control: Sustainability, hazards and cropping systems worldwide}, publisher={CRC Press/Taylor & Francis Group}, author={Leon, R.G. and Jordan, D.L. and Bolfrey-Arku, G. and Dzomeku, I.}, editor={Korres, N.E. and Burgos, N.R. and Duke, S.O.Editors}, year={2019}, pages={345–366} }
 @article{liu_kenworthy_macdonald_unruh_trenholm_leon_2019, title={Transgressive segregation and maternal genetic effects of non–target site fluazifop-P-butyl tolerance in Zoysia spp.}, volume={67}, url={https://doi.org/10.1017/wsc.2019.26}, DOI={10.1017/wsc.2019.26}, abstractNote={AbstractZoysia germplasm exhibit different levels of sensitivity to fluazifop-P-butyl, but the genetic factors responsible for such differences are unknown. Segregation patterns of the fluazifop-P-butyl tolerance trait were studied under greenhouse conditions. In total, 244 F1 lines were generated from multiple crosses between the tolerant line 5337-2 (non–target site tolerance) and three more-sensitive lines (123, 252, and 5330-23). Progeny segregation showed that fluazifop-P-butyl tolerance within zoysiagrass (Zoysia spp.) is expressed as a quantitative trait with a wide range of intermediate phenotypes between parental phenotypes. Transgressive segregation was extensive and largely favored susceptibility in most families, but was especially evident for 5337-2 × 123 and 5337-2 × 5330-23. The segregation patterns for biomass reduction and percent injury were different within reciprocal crosses and among three different family crosses. Reciprocal effects were observed in growth reduction for 5337-2 × 5330-23, in percent injury at 3 wk after the treatment (WAT), and for 5337-2 × 252 at 6 WAT. This indicated that fluazifop-P-butyl tolerance was not completely controlled by nuclear genetic factors in 5337-2 and maternal/cytoplasmic inheritance was also partially responsible. These results suggested that fluazifop-P-butyl tolerance may be attributed to multiple genetic mechanisms, which could present a challenge for future breeding efforts because of the difficulty of fixing multiple traits within a breeding population.}, number={05}, journal={Weed Science}, publisher={Cambridge University Press (CUP)}, author={Liu, Wenwen and Kenworthy, Kevin E. and MacDonald, Gregory E. and Unruh, J. Bryan and Trenholm, Laurie E. and Leon, Ramon G.}, year={2019}, month={Sep}, pages={504–509} }
 @article{liu_macdonald_unruh_kenworthy_trenholm_leon_2019, title={Variation in tolerance mechanisms to fluazifop-P-butyl among selected zoysiagrass lines}, volume={67}, ISSN={["1550-2759"]}, url={https://doi.org/10.1017/wsc.2019.6}, DOI={10.1017/wsc.2019.6}, abstractNote={AbstractBreeding herbicide tolerance into new cultivars can improve safety and weed control in turfgrass systems. The sensitivity to fluazifop-P-butyl of 27 zoysiagrass (Zoysiaspp.) lines was screened under greenhouse conditions to identify potential tolerant germplasm for breeding programs. The herbicide rate that caused 50% biomass reduction (GR50) and the rate that caused 50% injury (ID50) were calculated to select the three most-tolerant and the five most-susceptible lines for studying the physiological mechanisms responsible for fluazifop-P-butyl tolerance. The differences in GR50and ID50between susceptible and tolerant lines ranged from 4-fold to more than 10-fold. Cytochrome P450–mediated metabolism was not detected in fluazifop-P-butyl–tolerant lines. Sequencing of theACCasegene confirmed that none of the seven previously reported mutations conferring resistance to acetyl-CoA carboxylase (ACCase)-inhibiting herbicides in other species were present in any of the tolerant or susceptible zoysiagrass lines studied. An Ala-2073-Thr substitution was identified in two tolerant lines, but this mutation did not completely explain the tolerant phenotype. No clear differences in absorption and translocation rates of14C-radiolabeled fluazifop-P-butyl were observed among most lines, with the exception of a susceptible line that exhibited greater translocation than two of the tolerant lines. Metabolite profiles did not differ between tolerant and susceptible lines. Our results suggest that the diversity in tolerance to fluazifop-P-butyl in zoysiagrass germplasm is most likely the result of a combination of different, minor, additive non–target site mechanisms such as translocation rate and compartmentation after absorption.}, number={3}, journal={WEED SCIENCE}, publisher={Cambridge University Press (CUP)}, author={Liu, Wenwen and MacDonald, Gregory E. and Unruh, J. Bryan and Kenworthy, Kevin E. and Trenholm, Laurie E. and Leon, Ramon G.}, year={2019}, month={May}, pages={288–295} }
 @inbook{leon_odero_2019, edition={1}, title={Weed Management in Sugarcane}, booktitle={Weed control: Sustainability, hazards and cropping systems worldwide}, publisher={CRC Press/Taylor & Francis Group}, author={Leon, R.G. and Odero, D.C.}, editor={Korres, N.E. and Burgos, N.R. and Duke, S.O.Editors}, year={2019}, pages={455–469} }
 @article{jani_mulvaney_leon_rowland_erickson_wood_2018, title={Conventional harvest index methods may overestimate biomass and nutrient removal from abscising crop species}, volume={49}, DOI={10.1080/00103624.2018.1547390}, abstractNote={ABSTRACT Harvest index (HI) is conventionally measured using end-of-season biomass, but leaf abscission during crop growth can represent a substantial portion of total crop biomass for several species. A field study was conducted in Florida, USA, to determine the accuracy of conventional and alternative HI methods using sesame (Sesamum indicum L.) as a model species and to assess biomass and nutrient contributions from abscised leaves. Seed and nutrient HI was determined from three cultivars using the following four methods: (1) total biomass method that included both end-of-season and seasonal abscised biomass; (2) conventional method based solely on end-of-season biomass; (3) early-bloom method in which biomass collected during early-bloom stage was used as the nonseed biomass component; (4) mid-bloom method where biomass from mid-bloom stage was used for nonseed biomass. Early- and mid-bloom methods overestimated all HI and underestimated biomass and nutrient return to the soil. Most nutrient HI based on the conventional method was higher than the values based on the total biomass method. Compared to the total biomass method, the conventional method underestimated biomass and nutrient return to soil per ha by 714.8 kg biomass, 28.5 kg nitrogen, 3.6 kg phosphorus, 34.7 potassium, 4.6 magnesium, 25.7 calcium, 3.4 kg sulfur, 26.5 g boron, 361 g zinc, 25.9 g manganese, 527.2 g iron, and 18.7 g copper. Including abscised leaves when determining HI may not be feasible in field experiments due to labor constraints but is an option when measuring HI for species under similar management at regional scales to improve estimates of nutrient cycling.}, number={22}, journal={Communications in Soil Science and Plant Analysis}, publisher={Informa UK Limited}, author={Jani, A.D. and Mulvaney, M.J. and Leon, R.G. and Rowland, D.L. and Erickson, J.E. and Wood, C.W.}, year={2018}, pages={2889–2893} }
 @article{pearsaul_leon_sellers_silveira_odero_2018, title={Evaluation of verticutting and herbicides for tropical signalgrass (Urochloa subquadripara) control in turf}, volume={32}, DOI={10.1017/wet.2018.25}, abstractNote={AbstractTropical signalgrass (TSG) is one of the most problematic weeds found on golf courses, sports fields, and sod farms in south Florida. The recent ban of monosodium methane-arsonate (MSMA), an organic arsenical herbicide, from urban areas in Florida has left turfgrass managers searching for effective management options. In an effort to avoid relying solely on POST chemical control, this research examined the effect of combining a cultural practice, verticutting, along with PRE and POST herbicides as an integrated weed management approach to controlling TSG in hybrid bermudagrass. Field experiments were conducted at multiple locations over 2 yr in south Florida to: (1) determine whether verticutting before herbicide applications increases TSG control and (2) identify herbicide programs that effectively control TSG. No interactions between verticutting and herbicide programs were detected, but verticutting consistently provided a slight reduction (8% averaged across herbicide treatments) in TSG cover. Treatments containing a PRE herbicide resulted in a significant reduction (20% to 50%) in TSG cover at 52 wk after initial treatment (WAIT), while some POST herbicide treatments reduced TSG cover to <20% at 52 WAIT. A study was conducted to determine which POST herbicide combinations were most efficacious in controlling TSG. Amicarbazone alone provided ≤35% TSG control at 8 and 12 WAIT, but synergistic responses were observed between amicarbazone and mesotrione, trifloxysulfuron, and thiencarbazone+foramsulfuron+halosulfuron. Two- and three-way combinations of amicarbazone with these POST herbicides resulted in >80% TSG control at 4, 8, and 12 WAIT, with some reaching 100% TSG control at 4 WAIT. Based on these data, verticutting may provide limited complementary control, but certain combinations of POST herbicides exhibited excellent (>95%) TSG control.}, number={04}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Pearsaul, D.G. and Leon, R.G. and Sellers, B.A. and Silveira, M.L. and Odero, D.C.}, year={2018}, pages={392–397} }
 @article{reinhardt_leon_2018, title={Extractable and Germinable Seedbank Methods Provide Different Quantifications of Weed Communities}, volume={66}, ISSN={1550-2759}, url={https://www.cambridge.org/core/product/identifier/S0043174518000565/type/journal_article}, DOI={10.1017/wsc.2018.56}, abstractNote={AbstractSeedbank sampling and quantification methods vary in their ability to describe weed diversity and density, so proper method selection is critical for studying weed communities. The germinable seedbank (GSB) method is commonly preferred over extractable seedbank method (ESB), because the latter is more time-consuming. However, these two methods have only been compared using a few weed species and a relatively small number of samples. A total of 204 weed seedbank samples were used to compare both methods for weed density, richness, evenness, and Shannon-Weiner diversity using a split-sample approach. The two methods yielded dramatically different results. The ESB had 418% higher density and 35% more species per sample but 11% less evenness than the GSB. Diversity was estimated to be only 9% higher using the extractable compared with the germinable method. While the extractable method had higher density and richness overall, this was not true for every species, with only 7 of 14 common species detected in higher amounts by the extractable method. The results indicate the two methods are not strongly correlated, limiting the possibility of generating a conversion factor between methods. Nevertheless, evenness and Shannon-Weiner diversity might allow comparisons between both methods when the emphasis is on characterizing predominant weed species. The GSB is a practical approach to compare treatments or conditions; however, the ESB is more useful to accurately quantify weed species richness, diversity, and density.}, number={6}, journal={Weed Science}, publisher={Cambridge University Press (CUP)}, author={Reinhardt, Theresa and Leon, Ramon G.}, year={2018}, month={Nov}, pages={715–720} }
 @article{mulvaney_seepaul_small_wright_paula-moraes_crozier_cockson_whipker_leon_2018, title={Frost Damage of Carinata Grown in the Southeastern US}, volume={2018}, url={https://doi.org/10.32473/edis-ag420-2018}, DOI={10.32473/edis-ag420-2018}, abstractNote={Brassica carinata is an annual oilseed crop used for the commercial production of jet fuel. One of the challenges to commercialization of this crop in the southeastern United States has been frost damage. This 4-page fact sheet discusses symptomology and ways to minimize risk of frost damage to carinata. Written by Michael J. Mulvaney, Ramdeo Seepaul, Ian Small, David Wright, Silvana Paula-Moraes, Carl Crozier, Paul Cockson, Brian Whipker, and Ramon Leon, and published by the UF/IFAS Agronomy Department, May 2018. https://edis.ifas.ufl.edu/ag420}, number={3}, journal={EDIS}, publisher={University of Florida George A Smathers Libraries}, author={Mulvaney, Michael J. and Seepaul, Ramdeo and Small, Ian M. and Wright, David L. and Paula-Moraes, Silvana V. and Crozier, Carl and Cockson, Paul and Whipker, Brian and Leon, Ramon}, year={2018}, month={May} }
 @article{leon_laat_2018, title={Herbicidal and Seed Dormancy Induction Activity of Fermentation Residual Vinasse}, volume={66}, ISSN={["1550-2759"]}, DOI={10.1017/wsc.2017.84}, abstractNote={AbstractVinasse, a liquid fermentation residual of bio-ethanol production that also contains solid particles in suspension, is commonly used as a soil amendment. Previous studies reported vinasse reduced seed germination and seedling establishment, suggesting herbicidal activity. Laboratory experiments were conducted to determine whether vinasse herbicidal activity is present in the liquid or solid phase, and whether it affects plants during seed early germination (i.e., imbibition), late germination (i.e., embryo growth and radicle protrusion), or seedling growth. Most of the herbicidal activity was associated with the liquid phase, and for most species, seed viability was predominantly affected after the imbibition phase. Susceptibility to vinasse was species dependent. Lettuce (Lactuca sativaL.) germination was <8% when seeds were imbibed and germinated in vinasse solutions or imbibed in water and germinated in vinasse. Conversely, imbibing lettuce seeds in vinasse solutions and germinating them in water did not change their germination in comparison with seeds imbibed and germinated in water (>80% germination). Wheat (Triticum aestivumL.) and sicklepod [Senna obtusifolia(L.) H. S. Irwin & Barneby] germination decreased 10% and 35% when seeds were imbibed and germinated in vinasse, respectively, while Palmer amaranth (Amaranthus palmeriS. Watson) and southern crabgrass [Digitaria ciliaris(Retz.) Koeler] germination decreased >90%. All evaluated species reduced radicle growth as vinasse concentration increased. Filtered liquid vinasse with reduced concentration of salt and ionic compounds inhibited radicle growth similarly to unfiltered vinasse, indicating that the herbicidal activity was not due to osmotic effects and was likely present in the organic liquid phase.Amaranthus palmeri,S. obtusifolia, andD. ciliarisincreased the proportion of dormant seed more than 2-fold when they were imbibed or imbibed and germinated in vinasse solutions. Vinasse might be useful for weed management to reduce germinable weed seedbanks by increasing seedling mortality and seed dormancy either by properly timing of its application as a soil amendment or by purifying herbicidal compounds and using them directly for weed control.}, number={3}, journal={WEED SCIENCE}, publisher={Cambridge University Press (CUP)}, author={Leon, Ramon G. and Laat, Rocio}, year={2018}, pages={317–323} }
 @article{schroeder_barrett_shaw_asmus_coble_ervin_jussaume_owen_burke_creech_et al._2018, title={Managing herbicide resistance: Listening to the perspective of practitioners. Procedures for conducting listening sessions and an evaluation of the process}, volume={32}, DOI={10.1017/wet.2018.53}, abstractNote={AbstractSeven half-day regional listening sessions were held between December 2016 and April 2017 with groups of diverse stakeholders on the issues and potential solutions for herbicide-resistance management. The objective of the listening sessions was to connect with stakeholders and hear their challenges and recommendations for addressing herbicide resistance. The coordinating team hired Strategic Conservation Solutions, LLC, to facilitate all the sessions. They and the coordinating team used in-person meetings, teleconferences, and email to communicate and coordinate the activities leading up to each regional listening session. The agenda was the same across all sessions and included small-group discussions followed by reporting to the full group for discussion. The planning process was the same across all the sessions, although the selection of venue, time of day, and stakeholder participants differed to accommodate the differences among regions. The listening-session format required a great deal of work and flexibility on the part of the coordinating team and regional coordinators. Overall, the participant evaluations from the sessions were positive, with participants expressing appreciation that they were asked for their thoughts on the subject of herbicide resistance. This paper details the methods and processes used to conduct these regional listening sessions and provides an assessment of the strengths and limitations of those processes.}, number={04}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Schroeder, Jill and Barrett, Michael and Shaw, David R. and Asmus, Amy B. and Coble, Harold and Ervin, David and Jussaume, Raymond A. and Owen, Micheal D. K. and Burke, Ian and Creech, Cody F. and et al.}, year={2018}, pages={489–497} }
 @article{schroeder_barrett_shaw_asmus_coble_ervin_jussaume_owen_burke_creech_et al._2018, title={Managing wicked herbicide-resistance: Lessons from the field}, volume={32}, DOI={10.1017/wet.2018.49}, abstractNote={AbstractHerbicide resistance is ‘wicked’ in nature; therefore, results of the many educational efforts to encourage diversification of weed control practices in the United States have been mixed. It is clear that we do not sufficiently understand the totality of the grassroots obstacles, concerns, challenges, and specific solutions needed for varied crop production systems. Weed management issues and solutions vary with such variables as management styles, regions, cropping systems, and available or affordable technologies. Therefore, to help the weed science community better understand the needs and ideas of those directly dealing with herbicide resistance, seven half-day regional listening sessions were held across the United States between December 2016 and April 2017 with groups of diverse stakeholders on the issues and potential solutions for herbicide resistance management. The major goals of the sessions were to gain an understanding of stakeholders and their goals and concerns related to herbicide resistance management, to become familiar with regional differences, and to identify decision maker needs to address herbicide resistance. The messages shared by listening-session participants could be summarized by six themes: we need new herbicides; there is no need for more regulation; there is a need for more education, especially for others who were not present; diversity is hard; the agricultural economy makes it difficult to make changes; and we are aware of herbicide resistance but are managing it. The authors concluded that more work is needed to bring a community-wide, interdisciplinary approach to understanding the complexity of managing weeds within the context of the whole farm operation and for communicating the need to address herbicide resistance.}, number={04}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Schroeder, Jill and Barrett, Michael and Shaw, David R. and Asmus, Amy B. and Coble, Harold and Ervin, David and Jussaume, Raymond A. and Owen, Micheal D. K. and Burke, Ian and Creech, Cody F. and et al.}, year={2018}, pages={475–488} }
 @article{jani_mulvaney_enloe_erickson_leon_rowland_wood_2019, title={Peanut residue distribution gradients and tillage practices determine patterns of nitrogen mineralization}, volume={113}, DOI={10.1007/s10705-018-9962-2}, number={1}, journal={Nutrient Cycling in Agroecosystems}, publisher={Springer Nature}, author={Jani, A.D. and Mulvaney, M.J. and Enloe, H.A. and Erickson, J.E. and Leon, R.G. and Rowland, D.L. and Wood, C.W.}, year={2019}, pages={63–76} }
 @article{leon_wright_2018, title={Recurrent Changes of Weed Seed Bank Density and Diversity in Crop-Livestock Systems}, volume={110}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2017.11.0662}, abstractNote={Core Ideas
Crop phase can be used to modify weed diversity.Grazing in sod‐based rotations decreased Palmer amaranth seed bank.Weed seed banks respond rapidly to crop phase within diverse rotations.
Weeds are important biodiversity components in agroecosystems, but weed competition with cash crops requires farmers to manage weeds, limiting biodiversity within agricultural fields. Crop rotation increases weed diversity, but weeds are still managed in all cash crop phases so yields are not negatively affected. In our research, a bahiagrass (Paspalum notatum Flüggé)–bahiagrass–peanut (Arachis hypogaea L)–cotton (Gossypium hirsutum L.) rotation exhibited recurrent changes in weed seed banks. The bahiagrass crop phases increased, whereas peanut and cotton phases decreased weed density and diversity. Increasing weed seed banks in bahiagrass did not negatively impact the cash crops peanut and cotton. Furthermore, including grazing in the rotation did not affect overall weed seed banks, but caused a 75% reduction in Palmer amaranth (Amaranthus palmeri S. Watson) populations, the most problematic weed species in peanut and cotton. Our results indicate that grazing bahiagrass will promote weed diversity and suppress Palmer amaranth, resulting in better weed management in the peanut and cotton rotation crops.}, number={3}, journal={AGRONOMY JOURNAL}, publisher={American Society of Agronomy}, author={Leon, Ramon G. and Wright, David L.}, year={2018}, pages={1068–1078} }
 @article{leon_ferrell_mulvaney_2017, title={Carinata (Brassica carinata) tolerance to preemergence and postemergence herbicides}, volume={31}, DOI={10.1017/wet.2017.62}, abstractNote={Carinata is a new biofuel crop that was recently introduced in the southeastern USA as a winter crop. This crop is competitive after canopy closure, but there is a need for weed control options at earlier growth stages. Field experiments were conducted from 2014 to 2016 to determine the safety of several PRE and POST herbicides in carinata. Pendimethalin at 1080 g ai ha−1 applied preplant incorporated (PPI) and PRE caused no carinata injury, or plant density and yield reductions. S-metolachlor was also safe at 694, 1070, 1390, and 2780 g ai ha−1 applied at PRE, 3 d after planting (DAP) and at the 2- to 6-leaf stage. Flumioxazin at 72 g ai ha−1 applied PRE was highly injurious on carinata preventing its establishment. Among the POST herbicides evaluated, clopyralid at 210 g ae ha1 and clethodim at 136 g ai ha−1 caused minor injury to carinata but did not reduce yield compared to the nontreated control. Acifluorfen at 420 g ai ha−1, bentazon at 840 g ai ha−1, and carfentrazone at 18 g ai ha−1 applied POST to carinata caused 75 to 100% injury. Under stressful conditions (i.e. high summer temperatures) all POST herbicides caused more injury than under more favorable conditions for growth in Florida (i.e. winter). The present study identified pendimethalin, S-metolachlor, clopyralid and clethodim as potential herbicides for weed control in carinata, and flumioxazin, acifluorfen, bentazon, and carfentrazone as herbicides that can be used to control volunteer carinata plants in rotational crops.}, number={06}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Ferrell, J.A. and Mulvaney, M.J.}, year={2017}, pages={877–882} }
 @article{reyes-cabrera_erickson_leon_silveira_rowland_sollenberger_morgan_2017, title={Converting bahiagrass pasture land to elephantgrass bioenergy production enhances biomass yield and water quality}, volume={248}, DOI={10.1016/j.agee.2017.07.021}, abstractNote={Changing pasture land to the production of bioenergy crops will affect regional water dynamics. Returning by-products of industrial conversion of bioenergy crops like fermentation residual or biochar back to the field could be used to improve sustainable nutrient management, but could also impact water quantity and quality in ways that are poorly understood. The objective of this study was to assess the effects of land-use conversion from low-input bahiagrass (Paspalum notatum Flüggé) pastures to elephantgrass [Pennisetum purpureum (L.) Schum.] for bioenergy production under different nutrient management practices on biomass yield, crop water dynamics and nitrate-nitrogen (NO3-N) leaching during growing and dormant seasons. Treatments evaluated were 1) bahiagrass + 50 kg N ha−1; 2) elephantgrass + 50 kg N ha−1; 3) elephantgrass + 50 kg N ha−1 + fermentation residual; 4) elephantgrass + 50 kg N ha−1 + biochar; and 5) elephantgrass + 250 kg N ha−1. Data were collected on crop evapotranspiration (ET), water use efficiency, drainage, NO3-N leaching, and aboveground dry matter accumulation. Dry matter yield of elephantgrass was 4- to 7-fold greater than bahiagrass after the first growing season, but was similar among elephantgrass treatments. Elephantgrass produced with no residual amendments reduced drainage (approx. 43% across all growing seasons) compared to bahiagrass, and this reduction was exacerbated in the residual treatments. Reduced drainage was associated with increased ET. Elephantgrass, regardless of treatment, reduced the amount of NO3-N lost through drainage compared to bahiagrass. Therefore, replacing bahiagrass with elephantgrass will increase cropping system water use and diminish the rate of groundwater replenishment during the growing season, which could have detrimental effects for other ecosystem processes that rely on this water resource. However, elephantgrass increased the efficiency with which water was used to produce biomass and reduced NO3-N leaching to groundwater.}, journal={Agriculture Ecosystems and Environment}, publisher={Elsevier BV}, author={Reyes-Cabrera, J. and Erickson, JE and Leon, RG and Silveira, ML and Rowland, DL and Sollenberger, LE and Morgan, KT}, year={2017}, pages={20–28} }
 @article{reyes-cabrera_leon_erickson_rowland_silveira_morgan_2017, title={Differences in biomass and water dynamics between a cotton-peanut rotation and a sweet sorghum bioenergy crop with and without biochar and vinasse as soil amendments}, volume={214}, ISSN={["1872-6852"]}, DOI={10.1016/j.fcr.2017.09.012}, abstractNote={Land use conversion of row crops to bioenergy cropping systems in the southeastern United States (U.S.) creates concerns associated with water use and NO3-N leaching. Production of energy from biomass is associated with large amounts of byproducts generated during biofuel processing. Biochar and vinasse are two nutrient rich byproducts that could be land-applied to bioenergy crops to reduce reliance on synthetic fertilizer. However, effects on water dynamics of applying these byproducts to support biomass production is poorly understood, particularly when bioenergy crops replace traditional row crops. Thus, this study aimed to compare a cotton (Gossypium hirsutum L.)-peanut (Arachis hypogaea L.) rotation to sweet sorghum [Sorghum bicolor (L.) Moench] receiving annual applications of biochar and vinasse, on biomass yield, crop evapotranspiration, water use efficiency (WUE), NO3-N leaching, and soil volumetric water content. A field study was conducted from 2013 to 2015 to assess the following treatments: cotton + 150 kg N ha−1 (COT), peanut + 30 kg N ha−1 (PEA), and sweet sorghum receiving one of the following i) 30 kg N ha−1 (S30); ii) 30 kg N ha−1 + biochar (S30B); iii) 30 kg N ha−1 + vinasse (S30V); and iv) 150 kg N ha−1 (S150). Similar aboveground dry matter yields were obtained in 2013 and 2015 for cotton and all sweet sorghum treatments and were on average 19 Mg ha−1 for both years. S30 and S150 achieved similar yields. Sweet sorghum and COT exhibited the highest WUE (∼5 g kg−1). S30B increased soil moisture retention at 0–0.2 m depth 36, 29, and 24% in 2013, 2014, and 2015, respectively. Biochar incorporated at 0.15 m soil depth increased soil moisture retention down to 0.4 m. Low N rate application combined with biochar in S30B could represent an alternative management practice to minimize N leaching, recycle nutrients, and increase soil water retention if sweet sorghum were to be widely adopted by farmers in the southeastern U.S.}, journal={FIELD CROPS RESEARCH}, publisher={Elsevier BV}, author={Reyes-Cabrera, Joel and Leon, Ramon G. and Erickson, John E. and Rowland, Diane L. and Silveira, Maria L. and Morgan, Kelly T.}, year={2017}, month={Dec}, pages={123–130} }
 @article{bravo_leon_ferrell_mulvaney_wood_2017, title={Differentiation of Life-History Traits among Palmer Amaranth Populations (Amaranthus palmeri) and Its Relation to Cropping Systems and Glyphosate Sensitivity}, volume={65}, ISSN={["1550-2759"]}, DOI={10.1017/wsc.2017.14}, abstractNote={Palmer amaranth’s ability to evolve resistance to different herbicides has been studied extensively, but there is little information about how this weed species might be evolving other life-history traits that could potentially make it more aggressive and difficult to control. We characterized growth and morphological variation among 10 Palmer amaranth populations collected in Florida and Georgia from fields with different cropping histories, ranging from continuous short-statured crops (vegetables and peanut) to tall crops (corn and cotton) and from intensive herbicide use history to organic production. Palmer amaranth populations differed in multiple traits such as fresh and dry weight, days to flowering, plant height, and leaf and canopy shape. Differences between populations for these traits ranged from 36% up to 87%. Although glyphosate-resistant (GR) populations collected from cropping systems including GR crops exhibited higher values of the aforementioned variables than glyphosate-susceptible (GS) populations, variation in traits was not explained by glyphosate resistance or distance between populations. Cropping system components such as crop rotation and crop canopy structure better explained the differences among populations. The higher growth of GR populations compared with GS populations was likely the result of multiple selection forces present in the cropping systems in which they grow rather than a pleiotropic effect of the glyphosate resistance trait. Results suggest that Palmer amaranth can evolve life-history traits increasing its growth and reproduction potential in cropping systems, which explains its rapid spread throughout the United States. Furthermore, our findings highlight the need to consider the evolutionary consequences of crop rotation structure and the use of more competitive crops, which might promote the selection of more aggressive biotypes in weed species with high genetic variability.}, number={3}, journal={WEED SCIENCE}, publisher={Cambridge University Press (CUP)}, author={Bravo, Washington and Leon, Ramon G. and Ferrell, Jason A. and Mulvaney, Michael J. and Wood, C. Wesley}, year={2017}, pages={339–349} }
 @article{sperry_ferrell_smith_fernandez_leon_smith_2017, title={Effect of sequential applications of protoporphyrinogen oxidase (PPO) inhibiting herbicides on Palmer amaranth (Amaranthus palmeri) in peanut (Arachis hypogaea)}, volume={31}, DOI={10.1017/wet.2016.3}, abstractNote={Two experiments were conducted in 2013 and 2014 in Florida to evaluate the effects of protoporphyrinogen oxidase (PPO)-inhibiting herbicides and single versus sequential applications on Palmer amaranth control and peanut injury. Protoporphyrinogen oxidase-inhibiting herbicides are among the last available herbicides for the POST control of acetolactate synthase (ALS)-resistant Palmer amaranth in peanut. Lactofen (219 g ai ha–1) applied 5 d after the initial application provided the highest level of Palmer amaranth control 7 and 14 d after initial application (DAIT). Delaying sequential applications of lactofen to 15 d resulted in the highest level of Palmer amaranth control 21 and 28 DAIT. Similar to Palmer amaranth control, foliar injury to peanut was often highest from lactofen applications, and by 28 DAIT lactofen treatments were the only treatments that caused foliar injury. Although no statistical difference was observed between yields of plots treated with acifluorfen (280 g ai ha–1), bentazon (560 g ai ha–1), 2,4-DB (280 g ae ha–1) alone or in combination with each other, plots treated with sequential applications of lactofen 5 or 15 DAIT produced the lowest yields. Sequential applications of lactofen applied 15 DAIT controlled Palmer amaranth more effectively than any other treatment but also caused the highest level of peanut injury. The use of sequential applications of lactofen was the most effective method for control of Palmer amaranth in this study, but did reduce peanut yield.}, number={01}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Sperry, B.P. and Ferrell, J.A. and Smith, H.C. and Fernandez, V.J. and Leon, R.G. and Smith, C.A.}, year={2017}, pages={46–52} }
 @article{della torre_gettys_haller_ferrell_leon_2017, title={Efficacy of aquatic herbicides on rotala (Rotala rotundifolia)}, volume={55}, journal={Journal of Aquatic Plant Management}, author={Della Torre, C.J. and Gettys, L.A. and Haller, W.T. and Ferrell, J.A. and Leon, R.}, year={2017}, pages={13–18} }
 @article{bravo_leon_ferrell_mulvaney_wood_2018, title={Evolutionary Adaptations of Palmer Amaranth (Amaranthus palmeri) to Nitrogen Fertilization and Crop Rotation History Affect Morphology and Nutrient-Use Efficiency}, volume={66}, ISSN={["1550-2759"]}, DOI={10.1017/wsc.2017.73}, abstractNote={Palmer amaranth control has become a major challenge for multiple cropping systems across the southeastern and midwestern United States. Despite extensive research on herbicide-resistance evolution, little research has been done exploring how Palmer amaranth might also be evolving other adaptive traits in response to different selection forces present in agricultural fields and the enrichment of soils with nutrients such as nitrogen. The objective of the present study was to determine whether Palmer amaranth populations have evolved different morphology and growth patterns in response to glyphosate use and fertilization history. Ten Palmer amaranth populations, including glyphosate-resistant (GR) and glyphosate-susceptible (GS) populations, were collected from different cropping systems with histories of high and low nitrogen fertilization in the states of Florida and Georgia. All populations were grown in pots filled with soil fertilized with either 0 or 40 kgNha−1, and their response to nitrogen was compared for morphological, growth, and nutrient-use traits. Populations differed in how they modified their morphology and growth in response to N, with major differences in traits such as foliar area, branch production, leaf shape, and canopy architecture. Populations with high nitrogen-fertilization histories had higher (>43%) nutrient-use efficiency (NUE) than populations with low nitrogen-fertilization histories. Similarly, GR populations have evolved higher NUE (>47%) and changed canopy architecture more than GS populations in response to nitrogen fertilization. The results of the present study highlight the importance of paying more attention to adaptations to cultural practices that might increase weediness and how genetic changes in traits involved in morphology and metabolism might favor compensatory mechanisms increasing the fitness of the population carrying herbicide-resistant traits.}, number={2}, journal={WEED SCIENCE}, publisher={Cambridge University Press (CUP)}, author={Bravo, Washington and Leon, Ramon G. and Ferrell, Jason A. and Mulvaney, Michael J. and Wood, C. Wesley}, year={2018}, pages={180–189} }
 @article{yarborough_vendramini_silveira_sollenberger_leon_sanchez_oliveira_kuhawara_gomes_cecato_et al._2017, title={Impact of potassium and nitrogen fertilization on bahiagrass herbage accumulation and nutrient concentration}, volume={109}, DOI={10.2134/agronj2016.10.0589}, abstractNote={Core Ideas
Bahiagrass pastures on soils with low K concentration may not respond to K fertilization.
Tissue K concentration in bahiagrass is variable and dependent on fertilization levels.
Bahiagrass tissue K concentration of 17 g kg−1 was related to the greatest herbage accumulation in plants receiving greater levels of fertilization.
Bahiagrass (Paspalum notatum Flügge) is the most utilized forage for beef cattle (Bos spp.) in Florida, but there is concern that bahiagrass pastures are declining due to insufficient K fertilization. Two studies determined the effects of K and N fertilization on bahiagrass herbage mass (HM) and nutritive value in field plots (Exp. 1), and greenhouse (Exp. 2). At two locations from May to December 2014 and 2015, Exp. 1 evaluated the combinations of three N fertilization levels (0, 50 kg N ha−1 in May, or 50 kg N ha−1 in May and August) and two levels of K fertilization (0 or 42 kg K ha−1). Potassium fertilization did not affect HM, crude protein (CP), or in vitro digestible organic matter (IVDOM); however, tissue K concentration increased from 10.6 to 11.2 g kg−1 with increasing K fertilization. Plots fertilized with N had greater HM than the control, but there was no difference between plots fertilized in May only vs. those fertilized in May and August. Experiment 2 was conducted in a greenhouse in 2014 and 2015 with a factorial combination of three levels of N fertilization (0, 50, and 100 kg N ha−1) and four levels of K fertilization (0, 16, 33, and 66 kg K ha−1). There was a quadratic relationship between tissue K concentration and herbage accumulation (HA) and maximum HA occurred with tissue K concentration of 17 g kg−1. Bahiagrass tissue K concentration and response to K fertilization are variable and can be related to fertilization levels.}, number={3}, journal={Agronomy Journal}, publisher={American Society of Agronomy}, author={Yarborough, J.K. and Vendramini, J.M.B. and Silveira, M.L. and Sollenberger, L.E. and Leon, R.G. and Sanchez, J.M.D. and Oliveira, F. and Kuhawara, F. and Gomes, V. and Cecato, U. and et al.}, year={2017}, pages={1099–1105} }
 @article{yarborough_vendramini_silveira_sollenberger_leon_sellers_sanchez_leite de oliveira_kuhawara_gomes_et al._2017, title={Potassium and Nitrogen Fertilization Effects on Jiggs Bermudagrass Herbage Accumulation, Root–Rhizome Mass, and Tissue Nutrient Concentration}, volume={3}, ISSN={2374-3832}, url={https://dl.sciencesocieties.org/publications/cftm/abstracts/3/1/cftm2017.04.0029}, DOI={10.2134/cftm2017.04.0029}, abstractNote={Core Ideas
Bermudagrass K fertilization affects forage characteristics.
Bermudagrass K fertilization effects are influenced by N fertilization.
K fertilization is crucial to increase belowground reserves of bermudagrass.
Adequate supply of potassium (K) is an important factor that can affect bermudagrass [Cynodon dactylon (L.) Pers.] production and persistence, particularly in soils with limited nutrient holding capacity. The objectives of this study were to (i) evaluate the effects of different nitrogen (N) and K fertilization strategies on Jiggs bermudagrass herbage accumulation (HA), root–rhizome mass, and K concentration and accumulation in above‐ and belowground tissue; and (ii) identify the critical minimum tissue K concentration below which bermudagrass HA is reduced. The experiment was conducted in a greenhouse at Ona, FL, from August to December, 2014 and 2015. Treatments were a factorial combination of three N (0, 45, and 90 lb/acre) and four K2O fertilization levels (0, 18, 36, and 72 lb K2O/acre, the equivalent of 0, 15, 30, and 60 lb K/acre) after every harvest, distributed in a completely randomized design with four replicates. Herbage was harvested every 6 weeks, and root and rhizome mass determined at the end of each year. There were no effects of K fertilization on HA and root–rhizome mass when no N was applied; however, Jiggs HA and root–rhizome biomass increased linearly with increasing K fertilization levels at 45 and 90 lb N/acre. For these N levels, HA increased with tissue K concentration up to 1.4%. Root and rhizome K concentrations decreased linearly with increasing levels of N. Conversely, root–rhizome K content increased with increasing levels of N fertilization. Potassium fertilization increased HA and root–rhizome mass of Jiggs bermudagrass; however, the responses were influenced by N fertilization levels.}, number={1}, journal={Crop, Forage and Turfgrass Management}, publisher={American Society of Agronomy}, author={Yarborough, J.K. and Vendramini, J.M.B. and Silveira, M.L.A. and Sollenberger, L.E. and Leon, R.G. and Sellers, B. and Sanchez, JMD and Leite de Oliveira, F. and Kuhawara, F. and Gomes, V. and et al.}, year={2017}, pages={0} }
 @article{sperry_ferrell_leon_rowland_mulvaney_dias_2017, title={Sesame tolerance to preplant applications of 2,4-D and dicamba}, volume={31}, DOI={10.1017/wet.2017.37}, abstractNote={Two separate experiments were conducted in 2015 and 2016 in Citra, FL to investigate the effects of preplant application timing of 2,4-D and dicamba on sesame stand and yield. Nonlinear regression analysis was performed to determine the application timing that caused 10% stand or yield reduction (GR10) compared to the nontreated control (NTC) and expressed as d before planting (DBP; longer intervals indicate more injury). Likewise, regression analysis was used to determine sesame stand that resulted in 10% yield reduction (YR10) expressed as plants m−1row. Stand measured 3 wk after planting (WAP) revealed 2,4-D applied at 0.53 kg ae ha−1to be the least injurious treatment to sesame stand (GR10=6.4 DBP). Conversely, dicamba at 1.12 kg ha−1produced a GR10of 15.7 DBP for sesame stand at 3 WAP. 2,4-D applied at 0.53 and 1.06 kg ha−1and dicamba applied at 0.56 kg ha−1had the lowest GR10for yield of 2, 3.7, and 3 DBP, respectively. Dicamba applied at 1.12 kg ha−1proved to be the most injurious treatment to yield, which produced a GR10value of 10.3 DBP. To simulate possible stand losses associated with dicamba or 2,4-D and the subsequent effect on yield, a separate experiment was conducted in which sesame was thinned to various plant densities and yield was recorded to determine the relationship between plant stand and seed yield. The regression analysis of these data was then compared to that of the experiment treated with 2,4-D and dicamba to separate any physiological effects of the herbicides that would lead to yield reduction from yield effects due to stand loss only. Rate constants were compared and no statistical differences were detected between herbicide and non-herbicide treatments, suggesting that yield reductions that occur from preplant applications of 2,4-D and dicamba were purely due to stand reductions.}, number={04}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Sperry, B.P. and Ferrell, J.A. and Leon, R.G. and Rowland, D.L. and Mulvaney, M.J. and Dias, J.L.C.S.}, year={2017}, pages={590–598} }
 @article{abe_sellers_ferrell_leon_odero_2016, title={Bahiagrass tolerance to aminocyclopyrachlor in Florida}, volume={30}, DOI={10.1614/wt-d-16-00060.1}, abstractNote={Two varieties of bahiagrass were evaluated under Florida conditions for forage tolerance to the new herbicide, aminocyclopyrachlor (ACP), which is essential for product development decisions. Herbicide treatments included ACP alone at 70 and 140 g ai ha−1, ACP + chlorsulfuron at 69 + 27 and 138 + 54 g ai ha−1, ACP + 2,4-D amine at 70 + 532 g ai ha−1 and 140 + 1,064 g ai ha−1, ACP + triclopyr-amine at 70 + 140 g ai ha−1 and 140 + 280 g ai ha−1, and ACP + metsulfuron at 46 + 7, 78 + 12, and 168 + 26 g ai ha−1, and also included a nontreated check. ‘Argentine’ bahiagrass was the most tolerant forage species, and ‘Pensacola’ bahiagrass was sensitive to ACP + metsulfuron and initially to ACP + chlorsulfuron. Herbicide applications using ACP, when labeled, will likely provide good to excellent control of several weed species, with little long-term impact on bahiagrass forage production when the cultivar is known.}, number={04}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Abe, D.G. and Sellers, B.A. and Ferrell, J.A. and Leon, R.G. and Odero, D.C.}, year={2016}, pages={943–948} }
 @article{reyes-cabrera_leon_erickson_silveira_rowland_morgan_2017, title={Biochar changes root growth and root distribution of soybean during early vegetative stages}, volume={57}, DOI={10.2135/cropsci2016.01.0075}, abstractNote={A better understanding of changes in root growth and distribution when soil is treated with biochar is needed. The aim of this study was to assess root distribution responses when biochar is added to the soil. A greenhouse study was conducted to investigate the effects of topdressing or incorporating four biochar rates on soybean [Glycine max (L.) Merr.] root distribution during early vegetative stages grown in lysimeters (depth: 35 cm). On average, topdressing either 10 or 25 Mg biochar ha−1 increased root length density (RLD) 39% and root surface area (RSA) 36% in the 0‐ to 0.05‐m soil layer compared with the control. In the 0.05‐ to 0.15‐m soil layer, incorporation of 10 Mg ha−1 increased RLD 35%. Similarly, incorporation of either 10 or 25 Mg biochar ha−1 increased RSA 38% compared with the control. Incorporation of 25 and 50 Mg biochar ha−1 in the top 0.15 m of soil increased leaf area 29 and 31% compared with topdressing 50 Mg biochar ha−1 and with the control, respectively. Biochar increased soybean RLD, RSA, and leaf area, especially when incorporated into the soil. Overall, our findings indicate that biochar application and placement within the soil affects plant‐rooting distribution, which represents an important management practice to increase RLD and RSA. Future research should focus on evaluating biochar rates and application methods under field conditions.}, number={1}, journal={Crop Science}, publisher={Crop Science Society of America}, author={Reyes-Cabrera, J. and Leon, R.G. and Erickson, J.E. and Silveira, M.L. and Rowland, D.L. and Morgan, K.T.}, year={2017}, pages={454–461} }
 @article{leon_agüero_calderón_2017, title={Diversity and spatial heterogeneity of weed communities in a sugarcane cropping system in the dry tropics of Costa Rica}, volume={65}, DOI={10.1614/ws-d-16-00066.1}, abstractNote={Weed diversity, structure, and distribution within and outside agricultural fields affect not only ecological processes but also weed management strategies. We studied how areas managed differently within and outside the field determine weed communities in a sugarcane cropping system in the dry tropics of Costa Rica. A total of 120 weed species were detected, which was similar to surveys conducted in subtropical and temperate conditions. Weed species richness was highest in undisturbed field borders and lowest in rows and furrows. The area where tractors turn within the field (turn area) had similar richness compared with the borders, despite being one of the most disturbed management areas studied. The most predominant weed species were divided between generalists and species that exhibited clear preferences for management area or soil texture. Soil texture was more important for determining weed community structure than management area when considering weed species affecting weed control decisions. The results indicated that disturbance in the management area and, especially, weed control practices are critical factors affecting weed diversity, but availability of resources for weed growth such as nutrients, soil moisture, and light can mitigate some of the limitations imposed by weed control on weed diversity, especially in the turn area. Differences in weed communities between management areas within fields indicated the existence of conditions that favor key weed species, and this information can be used to anticipate their population growth and help determine when and where more intensive control should be implemented.}, number={01}, journal={Weed Science}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Agüero, R. and Calderón, D.}, year={2017}, pages={128–140} }
 @article{sperry_ferrell_leon_rowland_mulvaney_2016, title={Influence of planting depth and application timing on S-metolachlor injury in sesame (Sesamum indicum L.)}, volume={30}, DOI={10.1614/wt-d-16-00081.1}, abstractNote={Two experiments were conducted in 2015 at multiple locations in Florida to evaluate the effects of planting depth and application timing onS-metolachlor injury in sesame. In both studies, sesame responded negatively to increases inS-metolachlor rate. Altering sesame planting depth did not provide increased safety to PRES-metolachlor applications. Sesame establishment declined with increased planting depth, likely because of the physical inability of the small seed to emerge from the 3.8-cm depth. Delaying applications ofS-metolachlor by 3 or 6 d after planting (DAP) consistently improved sesame establishment. Applications 3 and 6 DAP resulted in 89 to 92% seedling emergence at 2 wk after planting (WAP), relative to 55 to 63% emergence whenS-metolachlor was applied the day of planting (0 DAP) or 3 days before (−3 DAP), respectively. Applications 3 DAP resulted in 21 and 2% plant stunting when evaluated 3 and 6 WAP, respectively, whereas all other timings caused 25 to 51% stunting. Yield was reduced 22 and 33% by the −3 DAP and 0 DAP application timings, respectively, whereas no reduction in yield was observed by the delayed application timings. Therefore, delaying applications ofS-metolachlor by 3 to 6 days will likely result in improved sesame seedling establishment and total seed yield.}, number={04}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Sperry, B.P. and Ferrell, J.A. and Leon, R.G. and Rowland, D.L. and Mulvaney, M.J.}, year={2016}, pages={958–964} }
 @article{leon_mulvaney_tillman_2016, title={Peanut cultivars differing in growth habit and canopy architecture respond similarly to weed interference}, volume={43}, DOI={10.3146/ps16-3.1}, abstractNote={ABSTRACT
               It has been proposed that crops can be improved to be more competitive with weeds by increasing their ability to suppress weed growth and reproduction. Weed suppressive ability is predominantly influenced by plant architectures that favor shading and rapid canopy closure. A three-yr field experiment was conducted in Jay, FL to assess the response of peanut cultivars with different growth habits to weed interference. Three cultivars (‘Bailey', erect growth and tall canopy height; ‘Georgia-06G', semi-bunch and intermediate height; ‘TUFRunner 727’, prostrate growth and intermediate height) and one advanced breeding line (‘UFT312’, very prostrate growth and short canopy height) were subjected to three weed interference levels: no interference, early season interference, and full-season interference. Results showed that, despite differences in growth habit, morphological response to weed interference was similar among peanut cultivars. All cultivars suppressed weed growth more than 76% in 2 of 3 yr. Peanut reduced reproductive growth and maintained vegetative growth under weed interference scenarios, and yields decreased as interference duration increased. Competitiveness of peanut to weeds could be improved by identification of lines that better balance translocation of photoassimilates favoring kernels over vegetative growth.}, number={2}, journal={Peanut Science}, publisher={American Peanut Research and Education Society}, author={Leon, R.G. and Mulvaney, M.J. and Tillman, B.L.}, year={2016}, pages={133–140} }
 @article{fennimore_slaughter_siemens_leon_saber_2016, title={Technology for automation weed control in specialty crops}, volume={30}, DOI={10.1614/wt-d-16-00070.1}, abstractNote={Specialty crops, like flowers, herbs, and vegetables, generally do not have an adequate spectrum of herbicide chemistries to control weeds and have been dependent on hand weeding to achieve commercially acceptable weed control. However, labor shortages have led to higher costs for hand weeding. There is a need to develop labor-saving technologies for weed control in specialty crops if production costs are to be contained. Machine vision technology, together with data processors, have been developed to enable commercial machines to recognize crop row patterns and control automated devices that perform tasks such as removal of intrarow weeds, as well as to thin crops to desired stands. The commercial machine vision systems depend upon a size difference between the crops and weeds and/or the regular crop row pattern to enable the system to recognize crop plants and control surrounding weeds. However, where weeds are large or the weed population is very dense, then current machine vision systems cannot effectively differentiate weeds from crops. Commercially available automated weeders and thinners today depend upon cultivators or directed sprayers to control weeds. Weed control actuators on future models may use abrasion with sand blown in an air stream or heating with flaming devices to kill weeds. Future weed control strategies will likely require adaptation of the crops to automated weed removal equipment. One example would be changes in crop row patterns and spacing to facilitate cultivation in two directions. Chemical company consolidation continues to reduce the number of companies searching for new herbicides; increasing costs to develop new herbicides and price competition from existing products suggest that the downward trend in new herbicide development will continue. In contrast, automated weed removal equipment continues to improve and become more effective.}, number={04}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Fennimore, S.A. and Slaughter, D.C. and Siemens, M.C. and Leon, R.G. and Saber, M.N.}, year={2016}, pages={823–37} }
 @article{soni_leon_erickson_ferrell_silveira_2015, title={Biochar decreases atrazine and pendimethalin preemergence herbicidal activity}, volume={29}, DOI={10.1614/wt-d-14-00142.1}, abstractNote={Biochar and vinasse are by-products of biofuel production that can be used as soil amendments. However, their addition to the soil might affect PRE herbicide activity. Although studies have shown that biochar has a high herbicide adsorption capacity, there is little information available about biochar effect on weed control especially under field conditions. Therefore, the objective of this study was to determine the influence of biochar and vinasse application on atrazine and pendimethalin availability and herbicide activity underin vitroand field conditions.In vitroatrazine and pendimethalin herbicidal activities were not influenced by vinasse addition, but biochar application reduced atrazine and pendimethalin injury for all evaluated species. A sorption experiment confirmed high affinity of biochar for atrazine and pendimethalin. Linear regression analysis showed that the slope for atrazine and pendimethalin adsorption was 16 and 4 times higher in soil with biochar than in soil alone. Under field conditions, biochar at 0.5 kg m−2reduced atrazine and pendimethalin weed control 75% and 60%, respectively. These results suggested that the use of biochar as a soil amendment in cropping system could decrease PRE herbicide efficacy. Therefore, mitigating practices such as the use of higher rates or reliance on POST herbicides and cultivation might be necessary to ensure proper weed control.}, number={03}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Soni, N. and Leon, R.G. and Erickson, J.E. and Ferrell, J.A. and Silveira, M.L.}, year={2015}, pages={359–366} }
 @article{leon_izquierdo_gonzález-andújar_2015, title={Characterization and modelling of itchgrass (Rottboellia cochinchinensis) biphasic seedling emergence patterns in the tropics}, volume={63}, DOI={10.1614/ws-d-14-00172.1}, abstractNote={Itchgrass is an aggressive weed species in tropical agroecosystems. Because of phytosanitary restrictions to exports, pineapple producers must use a zero tolerance level for this species. An understanding of itchgrass seedling emergence would help producers to better time POST control. The objective of the present study was to characterize itchgrass seedling emergence patterns and develop a predictive model. Multiple field experiments were conducted in four agricultural fields in Costa Rica between 2010 and 2011 for a total of 9 site-years. Itchgrass consistently showed a biphasic emergence pattern, with a first emergence phase that was faster and more consistent across site-years than the second one. Weibull + logistic models based on chronological time (R2adj= 0.92) and thermal time withTbase= 20 C (R2adj= 0.92) provided the best fit for the combined emergence data for two experimental locations in 2010. Both models predicted itchgrass seedling emergence adequately for most site-years, but the thermal-time model was more accurate (R2adj= 0.64 to 0.86) than the chronological model (R2adj= 0.31 to 0.74), especially when temperatures were high. Both models showed high accuracy in the first emergence phase but tended to underestimate emergence rate during the second phase. The models predicted 50% emergence at 14 d or 80 growing degree days and the stabilization of the first emergence phase at approximately 25 d or 200 growing degree days. Thus, these models can be used to properly time itchgrass POST control. More research is needed to understand the regulatory mechanisms responsible for the variability of the second emergence phase.}, number={03}, journal={Weed Science}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Izquierdo, J. and González-Andújar, J.L.}, year={2015}, pages={623–630} }
 @article{laat r_owen_liebman_leon_2015, title={Post-dispersal weed seed predation and invertebrate activity-density in three tillage regimes}, volume={63}, DOI={10.1614/ws-d-15-00030.1}, abstractNote={Field experiments were conducted near Boone, IA, to quantify postdispersal seed predation of common lambsquarters and common waterhemp in corn (2003) and soybean (2004) managed with conventional, reduced, and zero-tillage systems. Seed predation in each tillage regime was quantified using selective exclusion treatments during July through September 2003 and June through October 2004. In addition, the activity density of ground-dwelling invertebrates was estimated with pitfall traps. Choice and no-choice feeding trials were conducted in the laboratory using the most abundant weed seed predators found in the field to determine seed preferences of the potential predator organisms. The greatest seed loss occurred during July and August. In 2003, seed predation was lower in zero tillage than in conventional and reduced tillages, but no differences in seed predation between tillage regimes were observed in 2004. Maximum seed predation for common lambsquarters was 53% in 2003 and 64% in 2004. Common waterhemp seed predation reached 80% in 2003 and 85% in 2004. The majority of seed predation was by invertebrate organisms. The most common invertebrate species captured with pitfall traps were field crickets (Gryllus pennsylvanicusDe Geer [Gryllidae, Orthoptera]) and ground beetles (Harpalus pensylvanicusBurmeister [Coleoptera, Carabidae]). In 2003, field crickets were relatively more abundant in conventional and reduced tillage than in zero-tillage plots. In 2004, field crickets were more abundant in the reduced tillage than in the other two tillage regimes. No differences were detected for ground beetles among tillage regimes (P = 0.57). Choice and no-choice feeding experiments confirmed the preferences of field crickets and ground beetles for common lambsquarters and common waterhemp seeds over the larger seeds of giant foxtail and velvetleaf. Under field conditions, the activity density of field crickets was a significant predictor of common lambsquarters (r2= 0.47) and common waterhemp (r2= 0.53) seed predation. Positive relationships were also detected between the activity density of ground beetles and common lambsquarters (r2= 0.30) and common waterhemp (r2= 0.30) seed predation. This research demonstrated that weed seed predation is an important component affecting weed seedbanks and that crop management practices that favor the activity of predators such as field crickets or ground beetles could influence weed populations. Also, the results suggested that tillage is more important in determining the number of weed seeds available on the soil surface to predators than directly affecting predator activity density.}, number={04}, journal={Weed Science}, publisher={Cambridge University Press (CUP)}, author={Laat R, Van Der and Owen, M.D.K. and Liebman, M. and Leon, R.G.}, year={2015}, pages={828–838} }
 @article{leon_tillman_2015, title={Postemergence herbicide tolerance variation in peanut germplasm}, volume={63}, DOI={10.1614/ws-d-14-00128.1}, abstractNote={Although herbicide tolerance is not usually evaluated until the final stages of breeding programs, this trait is very important for grower adoption of new peanut cultivars. Understanding herbicide tolerance of breeding lines could help breeders develop selection strategies that maximize herbicide tolerance in new commercial cultivars. However, little is known about herbicide tolerance variability in peanut germplasm. Thirty-five randomly selected breeding lines from the peanut mini-core collection and cultivars ‘Florida-07’ and ‘Georgia-06G’ were evaluated for tolerance to 11 herbicides under greenhouse conditions. Variation among peanut lines in herbicide tolerance, measured as dry weight reductions (DWR), was similar across herbicides and was normally distributed. Florida-07 and Georgia-06G were in the lower two quartiles of injury and DWR among the evaluated peanut lines. Dose–response experiments showed that the most tolerant breeding lines had I50(the rate required to cause 50% injury) and GR50(the rate required to reduce dry weight 50%) values 0.4 to 2.5 times higher than the most susceptible lines, depending on the herbicide. A breeding line had a dicamba GR5013 times higher than the most susceptible line and 2.8 and 4.7 times higher than Florida-07 and Georgia-06G, respectively. The most tolerant lines were consistently tolerant to herbicides with different mechanisms of action, suggesting that nontarget site mechanisms are more likely to be responsible for the tolerance than target-site mutations. These results confirmed peanut-breeding programs would greatly benefit from screening breeding lines for tolerance to key herbicides and developing an herbicide-tolerance catalog. This information can be used when designing new crosses to reduce the risk of developing cultivars with low herbicide tolerance especially considering that one-half of the breeding lines exhibited lower tolerance than the commercial cultivars.}, number={02}, journal={Weed Science}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Tillman, B.L.}, year={2015}, pages={546–554} }
 @article{leon_unruh_brecke_2016, title={Relative lateral movement in surface soil of amicarbazone and indaziflam compared to other preemergence herbicide for turfgrass}, volume={30}, DOI={10.1614/wt-d-15-00126.1}, abstractNote={Amicarbazone and indaziflam are relatively new herbicides that provide effective control of important weed species in turfgrass. A concern for golf course superintendents and turfgrass managers is the lack of information about runoff risk of these two herbicides, which is a limitation to their proper and safe use. The objectives of this research were (1) to compare lateral movement in surface soil of amicarbazone and indaziflam to other commonly used PRE herbicides in turfgrass (i.e., dithiopyr, prodiamine, pronamide, simazine) and (2) to determine whether incorporating the herbicide with irrigation before a simulated storm event reduces lateral movement. Herbicides were applied at full label rates in two locations (Jay and Milton, FL) with 14% slope, and lateral movement was evaluated using perennial ryegrass and annual bluegrass as bioindicators. Incorporating PRE herbicides with irrigation a few hours before a major simulated storm event did not reduce lateral movement of any of the herbicides evaluated. All herbicides moved outside the treated area regardless of the presence of a simulated storm event. Herbicide lateral movement varied from 61 to 153 cm in Jay, and from 5 to 103 cm in Milton. The Milton location had higher sand content and lower organic matter content than Jay, which favored water infiltration. No herbicide effects were observed 210 cm downslope from the treated area. On the basis of our results, the ranking from highest to lowest lateral movement was pronamide > simazine ≥ indaziflam > amicarbazone ≥ dithiopyr > prodiamine. The difference in lateral movement was approximately 60 to 80 cm between pronamide and prodiamine depending on location and evaluation timing for the 14% slope at the study sites. The results of the present study provide guidance for golf course superintendents and turfgrass managers to determine buffer zones in sensitive areas.}, number={01}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Unruh, J.B. and Brecke, B.J.}, year={2016}, pages={229–237} }
 @article{leon_ferrell_sellers_2016, title={Seed production and control of sicklepod (Senna obtusifolia) and pitted morningglory (Ipomoea lacunosa) with 2,4-D, dicamba, and glyphosate combinations}, volume={30}, DOI={10.1614/wt-d-15-00108.1}, abstractNote={Sicklepod and pitted morningglory are two of the most important weed species in row-crop production in the southeastern United States. The upcoming introduction of soybean and cotton varieties resistant to 2,4-D and dicamba will increase the reliance on these auxinic herbicides. However, it is not clear how these herbicides will affect sicklepod and pitted morningglory control. Field experiments were conducted in 2013 and 2014 in Jay, FL to determine whether 2,4-D (560 and 1,120 g ae ha−1), dicamba (420 and 840 g ae ha−1), and glyphosate (1,060 g ae ha−1) alone or in combination applied when weed shoots were 11 (early POST [EPOST]) and 22 (late POST [LPOST]) cm long effectively control and prevent seed production of sicklepod and pitted morningglory. LPOST provided more effective control of sicklepod than EPOST. This was attributed to emergence of sicklepod seedlings after the EPOST application. When glyphosate was tank mixed with 2,4-D or dicamba, sicklepod control was higher (78 to 89% and 87 to 98% in 2013 and 2014, respectively) than for single-herbicide treatments (45 to 77% and 38 to 80% in 2013 and 2014, respectively) 6 wk after treatment (WAT). Pitted morningglory control was not affected by application timing, and 2,4-D provided 91 to 100% 6 WAT, which was equivalent to treatments with tank mixtures containing glyphosate. Dicamba applied at 420 g ha−1had the lowest pitted morningglory control (44 to 70% and 82 to 86% in 2013 and 2014, respectively). Sicklepod and pitted morningglory plants that survived and recovered from herbicide treatments produced the same number of viable seeds as nontreated plants in most treatments. The results of the present study indicated that the use of 2,4-D and dicamba alone will not provide adequate extended control of sicklepod, and the use of tank mixtures that combine auxinic herbicides with glyphosate or other POST herbicides will be necessary to manage sicklepod adequately in 2,4-D- or dicamba-resistant soybean and cotton. Because sicklepod plants that survived a single herbicide application are capable of producing abundant viable seeds, integrated approaches that include PRE herbicides and sequential POST control options may be necessary to ensure weed seed bank reductions.}, number={01}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Ferrell, J.A. and Sellers, B.A.}, year={2016}, pages={76–84} }
 @article{berger_ferrell_dittmar_leon_2015, title={Survey of Glyphosate- and Imazapic-Resistant Palmer Amaranth (Amaranthus palmeri) in Florida}, volume={1}, ISSN={2374-3832}, url={https://dl.sciencesocieties.org/publications/cftm/abstracts/1/1/cftm2015.0122}, DOI={10.2134/cftm2015.0122}, abstractNote={Herbicide‐resistant Palmer amaranth (Amaranthus palmeri S. Wats.) is the most troublesome weed in Florida cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) production. In 2012, Palmer amaranth populations were surveyed to document the extent and level of resistance to glyphosate and imazapic. Mature seedheads were sampled at 31 locations in the northwest region of Florida where cotton and peanut are predominantly produced, and in the north‐central region of Florida that mainly consists of peanut production. Palmer amaranth plants were grown from field‐collected seed in the greenhouse and treated with glyphosate and imazapic to establish a dose response for each population. Glyphosate‐resistant Palmer amaranth was found in 11 populations that were located primarily in the northwest region, with some populations having up to 30‐fold resistance. Imazapic resistance was much more widespread, being found in 29 of the 30 populations tested. Since peanut production in Florida has historically relied on successive imazapic applications, it is not surprising that widespread resistance to imazapic has developed. Resistance to both herbicides was found in 10 populations. Results from this survey reveal the magnitude of herbicide resistance in Florida and the need for growers to diversify management strategies in the future.}, number={1}, journal={Crop, Forage & Turfgrass Management}, publisher={American Society of Agronomy}, author={Berger, Sarah T. and Ferrell, Jason A. and Dittmar, Peter J. and Leon, Ramon}, year={2015}, pages={0} }
 @article{abe_sellers_ferrell_leon_odero_2016, title={Tolerance of bermudagrass and stargrass toaminocyclopyrachlor}, volume={30}, DOI={10.1614/wt-d-15-00167.1}, abstractNote={The tolerance of bermudagrass and stargrass to the relatively new herbicide, aminocyclopyrachlor (ACP), must be known before it can be recommended for weed control in these forage systems. Field experiments were conducted in 2012 and 2013 in south-central Florida to determine the tolerance of established bermudagrass and stargrass to various rates and combinations of ACP, chlorsulfuron, 2,4-D, triclopyr, and metsulfuron. Overall, bermudagrass and stargrass injury was transient and was minimal by 60 d after treatment (DAT). Similarly, biomass production was negatively affected at 30 DAT when treated with ACP at rates of 70 g ae ha−1 or greater, but was similar to the nontreated control by 60 DAT. Tank-mixing ACP with chlorsulfuron, 2,4-D amine, triclopyr, or metsulfuron did not increase injury compared with ACP alone applied at equivalent rates. Forage nutritive values were unaffected by herbicides. These data suggest that long-term effects of ACP on bermudagrass and stargrass are negligible, and this herbicide could be an important component of weed management programs in these forage systems.}, number={02}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Abe, D.G. and Sellers, B.A. and Ferrell, J.A. and Leon, R.G. and Odero, D.C.}, year={2016}, pages={499–505} }
 @article{abe_sellers_ferrell_leon_odero_2016, title={Weed control in Florida pastures using aminocyclopyrachlor}, volume={30}, DOI={10.1614/wt-d-15-00052.1}, abstractNote={Studies under Florida conditions for susceptibility of pasture weed species to the new herbicide, aminocyclopyrachlor (ACP), are essential. Sensitivity of weed species was dependent upon the species and environment. Whitehead broom was not susceptible to ACP. Dogfennel control was consistently above 85% 1 yr after treatment with ACP at 140 g ha−1 and all ACP premixes. Milkpea was initially sensitive to all ACP treatments, but regrowth was evident in all treatments after 1 yr at one location. All ACP treatments resulted in 100% control of tropical soda apple 1 yr after treatment at one location, but less than 50% control at a second location. Herbicide applications with ACP, when labeled, will likely provide good to excellent control (80 to 100%) of several weed species.}, number={01}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Abe, D.G. and Sellers, B.A. and Ferrell, J.A. and Leon, R.G. and Odero, D.C.}, year={2016}, pages={271–278} }
 @article{leon_wright_marois_2015, title={Weed seed banks are more dynamic in a sod-based than a conventional peanut-cotton rotation}, volume={63}, DOI={10.1614/ws-d-15-00003.1}, abstractNote={Crop rotation promotes productivity, nutrient cycling, and effective pest management. However, in row-crop systems, rotation is frequently limited to two crops. Adding a third crop, especially a perennial crop, might increase crop-rotation benefits, but concerns about disruption of agricultural and ecological processes preclude grower adoption of a three-crop rotation. The objective of the present research was to determine whether weed seed banks differ between a sod-based rotation (bahiagrass–bahiagrass–peanut–cotton) and a conventional peanut–cotton rotation (peanut–cotton–cotton) and the importance of crop phase in weed seed-bank dynamics in a long-term experiment initiated in 1999 in Florida. Extractable (ESB) and germinable (GSB) seed banks were evaluated at the end of each crop phase in 2012 and 2013, and total weed seed or seedling number, Shannon-Weiner's diversity (H′), richness, and evenness were determined. ESB increased in H′ (36%), richness (29%), and total number of weed seeds (40%) for sod-based compared with conventional rotation, whereas GSB increased 32% in H′, 27% in richness, and 177% in total number of weed seedlings. Crop phase was a determinant factor in the differences between crop rotations. The first year of bahiagrass (B1) exhibited increases in weed seed and seedling number, H′, and richness and had the highest values observed in the sod-based rotation. These increases were transient, and in the second year of bahiagrass (B2), weed numbers and H′ decreased and reached levels equivalent to those in the conventional peanut–cotton rotation. The B1 phase increased the germinable fraction of the seed bank, compared with the other crop phases, but not the total number of weed seeds as determined by ESB. The increases in H′ and richness in bahiagrass phases were mainly due to grass weed species. However, these grass weed species were not associated with peanut and cotton phases of the sod-based rotation. The results of the present study demonstrated that including bahiagrass as a third crop in a peanut–cotton rotation could increase weed community diversity, mainly by favoring increases in richness and diversity, but the structure and characteristics of the rotation would prevent continuous increases in the weed seed bank that could affect the peanut and cotton phases.}, number={04}, journal={Weed Science}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Wright, D.L. and Marois, J.J.}, year={2015}, pages={877–887} }
 @article{leon_mccarty_estes_2014, title={Amicarbazone Application Timing Influences Overseeded Perennial Ryegrass (Lolium perenne) Safety and Annual Bluegrass (Poa annua) Control}, volume={11}, ISSN={1552-5821}, url={https://www.agronomy.org/publications/ats/abstracts/11/1/ATS-2014-0042-RS}, DOI={10.2134/ATS-2014-0042-RS}, abstractNote={Amicarbazone controls annual bluegrass (Poa annua L.) in bermudagrass [Cynodon dactylon (L.) Pers.] turf overseeded with perennial ryegrass (Lolium perenne L.). There is, however, a risk of perennial ryegrass injury, depending on application timing. The objective of this research was to determine the effect of the timings between overseeding and amicarbazone applications on perennial ryegrass. Amicarbazone was applied at 0, 2.1, and 2.8 oz a.i./acre at 6, 8, 10, and 12 weeks after overseeding (WAOS) in Florida and South Carolina. In Florida, perennial ryegrass maximum injury was greater at 6 WAOS (79%) than at 8 to 12 WAOS (6 to 30%). Conversely, in South Carolina, minor perennial ryegrass injury was observed in plots treated 6 to 10 WAOS, but 48% injury was observed in plots treated 12 WAOS. In all sites, plots treated at 6 WAOS exhibited up to fourfold reduction in perennial ryegrass cover compared with the untreated control (88%). Overall, annual bluegrass control was acceptable to excellent (73–99%) with amicarbazone applications in South Carolina. In Florida 24 weeks after initial treatment, all treatments controlled annual bluegrass 64 to 98% except applications at 6 WAOS (25–42%). Results suggest that amicarbazone should be applied at least 8 to 10 WAOS to minimize loss of perennial ryegrass cover, but applications at this time will provide adequate annual bluegrass control.}, number={1}, journal={Applied Turfgrass Science}, publisher={American Society of Agronomy}, author={Leon, Ramon G. and McCarty, Lambert B. and Estes, Alan G.}, year={2014}, pages={0} }
 @article{leon_unruh_brecke_kenworthy_2014, title={Characterization of fluazifop-P-butyl tolerance in zoysiagrass cultivars}, volume={28}, DOI={10.1614/wt-d-13-00142.1}, abstractNote={POST control of grass weed species and contaminant turfgrass species, such as common and hybrid bermudagrass, is a major challenge in zoysiagrass. Fluazifop-P-butyl is a POST herbicide that can provide selective grass weed control with limited injury to zoysiagrass. However, because of the extent of genetic variation among zoysiagrass cultivars, it was proposed that fluazifop-P-butyl tolerance was cultivar dependent. Dose–response field studies were conducted in Jay, FL, in 2012 and 2013, evaluating the tolerance of 11 commercial zoysiagrass cultivars and common bermudagrass to 0, 44, 88, 131, 175, and 263 g ai ha−1of fluazifop-P-butyl. ‘Empire' and ‘Meyer' zoysiagrass were injured 30% or less at 2 wk after treatment (WAT) when treated with 131 g ha−1of fluazifop-P-butyl or less. Conversely, ‘Zeon' and ‘PristineFlora' reached from 30 to more than 50% injury between 2 and 4 WAT with 44 and 88 g ha−1fluazifop-P-butyl. ‘Geo', ‘Crowne', ‘JaMur', and ‘UltimateFlora' showed intermediate injury (i.e. ≤ 60% with 175 and 264 g ha−1) and a recovery period longer than 4 WAT. ‘Emerald', ‘Palisades', and ‘Royal' also showed intermediate injury (i.e., 30 to 65% with 175 and 264 g ha−1), which peaked at 2 WAT and then rapidly declined below 25% injury at 4 WAT. By 8 WAT, all zoysiagrass cultivars had recovered, and no injury was observed. Results from a greenhouse experiment demonstrated that differences observed in the field were cultivar related, especially for the lower tolerance level observed in Zeon and PristineFlora. There is potential to increase fluazifop-P-butyl tolerance in zoysiagrass because of the observed variation among 80 zoysiagrass breeding lines.}, number={02}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Unruh, J.B. and Brecke, B.J. and Kenworthy, K.E.}, year={2014}, pages={385–394} }
 @article{leon_gilbert_comstock_2015, title={Energycane (Saccharum spp. × S. spontaneum) biomass production, reproduction and weed risk assessment scoring in the humid tropics and subtropics}, volume={107}, DOI={10.2134/agronj14.0388}, abstractNote={There is growing interest in biofuel production, and energycane (Saccharum spp. × S. spontaneum L.) has been proposed as an important biofuel and biomass crop. However, little is known about the growth and ecology of this new crop, especially in the tropics. The present study evaluated the performance of 14 energycane clones, elephantgrass (Pennisetum purpureum Schumach.), and two sugarcane (S. officinarum L.) varieties in the humid tropics of Costa Rica, and eight energycane clones in the subtropics of Florida. In the tropics, energycane's growth and biomass production were highly variable when comparing clones. However, the best performing clones US85‐1006, US88‐1006, and US78‐1014 produced almost twice the dry biomass (>64 Mg ha−1) compared with sugarcane varieties Pindar and Q‐132 (21–39 Mg ha−1). In the subtropics, energycane fresh (52–79 Mg ha−1) and dry (20–30 Mg ha−1) weights were less than half of those in the tropics. Energycane clones flowered in both environments, but pollen viability was three to four times higher (>40%) in the tropics than in the subtropics, although viable seeds were found only in the tropics. Weed risk assessment (WRA) scores were higher in the tropics than in the subtropics and varied among clones. The results confirmed that energycane is a promising feedstock for biomass production and could play an important role as a bioenergy crop when grown in the tropics and subtropics, but due to genotype × environment interactions, the tradeoff between biomass production and weedy and invasive risk must be assessed for each individual clone and environment.}, number={1}, journal={Agronomy Journal}, publisher={American Society of Agronomy}, author={Leon, R.G. and Gilbert, R.A. and Comstock, J.C.}, year={2015}, pages={323–329} }
 @article{leon_ferrell_brecke_2014, title={Impact of exposure to 2,4-D and dicamba on peanut injury and yield}, volume={28}, DOI={10.1614/wt-d-13-00187.1}, abstractNote={The potential widespread adoption of cotton and soybean varieties with 2,4-D and dicamba resistance traits in the southeastern US will increase the risk of accidental exposure of peanut to these herbicides because of drift or application errors. When such accidents occur, growers must decide between continuing the crop and terminating it. In order to make this decision, growers need to estimate the potential yield reduction caused by 2,4-D or dicamba. Dose-response studies were conducted under field conditions in Citra and Jay, FL in 2012 and 2013 to determine peanut injury and yield reduction after exposure to 70, 140, 280, 560, and 1120 g ae ha−1of 2,4-D or to 35, 70, 140, 280, and 560 g ae ha−1of dicamba at 21 and 42 d after planting (DAP). Only herbicide by rate interactions were significant (P < 0.04). Dicamba caused 2 to 5 times higher peanut injury and 0.5 to 2 times higher yield reductions than 2,4-D. Injury ranged from 0 to 35% when peanut plants were treated with 2,4-D and from 20 to 78% with dicamba. The maximum yield reduction was 41% with 1,120 g ha−1of 2,4-D and 65% with 560 g ha−1of dicamba. Linear regression indicated that the intercept for yield reduction was 12% for 2,4-D and 23% for dicamba, and there was a 2.5% and 7.7% increase in yield reduction per additional 100 g ha−1, respectively. Although high variability was observed for the different variables, there was a positive correlation between injury and peanut yield reduction (P < 0.0001) with Pearson's Rho values ranging from 0.45 to 0.59 for 2,4-D and from 0.27 to 0.55 for dicamba, suggesting that growers can use injury data to make rough projections of yield reduction and decide if they continue their crop, especially when injury is evident.}, number={03}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Ferrell, J.A. and Brecke, B.J.}, year={2014}, pages={465–470} }
 @article{ferrell_sellers_leon_2014, title={Management of spreading pricklypear (Opuntia humifusa) with fluroxypyr and aminopyralid}, volume={28}, DOI={10.1614/wt-d-14-00041.1}, abstractNote={Experiments were conducted throughout central Florida from 2010 to 2014 to determine the effectiveness of fluroxypyr or aminopyralid for control of spreading pricklypear. Aminopyralid + 2,4-D (0.09 + 0.75 kg ae ha−1) was not effective and provided only 15% control by 18 mo after application (MAT). However, fluroxypyr at 0.55 kg ae ha−1or sequential applications of 0.27 kg ha−1provided greater than 82% control at 18 MAT. Reducing fluroxypyr rates to 0.32 kg ha−1reduced control to 40 and 71% for spring versus fall applications, respectively. However, the addition of aminopyralid + 2,4-D to fluroxypyr at 0.32 kg ha−1improved pricklypear control to 92%, regardless of application timing.}, number={04}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Ferrell, J.A. and Sellers, B. and Leon, R.}, year={2014}, pages={734–738} }
 @article{arvai_kellon_leon_gregory_richardson_2014, title={Structuring international development decisions: Confronting tradeoffs between land-use and community development in Costa Rica}, volume={34}, DOI={10.1007/s10669-014-9495-4}, number={2}, journal={Environmental Systems and Decisions}, publisher={Springer Nature}, author={Arvai, J. and Kellon, D. and Leon, R. and Gregory, R. and Richardson, R.}, year={2014}, pages={224–236} }
 @article{soni_leon_erickson_ferrell_silveira_giurcanu_2014, title={Vinasse and biochar effects on germination and growth of Palmer amaranth (Amaranthus palmeri), sicklepod (Senna obtusifolia) and southern crabgrass (Digitaria ciliaris)}, volume={28}, DOI={10.1614/wt-d-14-00044.1}, abstractNote={Vinasse and biochar are by-products of biofuel production that can be used as sources of nutrients to crops or soil amendments to improve soil quality. Despite the recent interest in biochar and vinasse effects on soil properties, little is known about their effect on weed communities. We hypothesized that the addition of biochar and vinasse to the soil could affect weed seed germination and growth, and that different weed species would show different responses to these soil amendments. Therefore, the objectives of this study were to determine the effects of vinasse and biochar on the germination and growth of Palmer amaranth, sicklepod, and southern crabgrass. The study was conducted under laboratory and growth chamber conditions. Treatments consisted of four levels of vinasse (0, 10, 20, and 40 L m−2) and biochar (0, 0.5, 2.5, and 12.5 kg m−2) applied to a sandy loam soil. Biochar at 0.5 and 2.5 kg m−2increased germination of Palmer amaranth but had no effect on sicklepod and southern crabgrass. Vinasse reduced germination of all species. However, sicklepod germination was less affected by vinasse at 10 and 20 L m−2than the other two species. Vinasse at 40 L m−2decreased Palmer amaranth, southern crabgrass and sicklepod germination 57, 26 and 87%, respectively. Biochar had no consistent effect on the vegetative growth of the species studied. Vinasse at 10 L m−2stimulated growth of sicklepod and southern crabgrass compared to the nontreated control. Our results suggested that vinasse used as a soil amendment could affect weed community structure by decreasing germination of susceptible species, but plants and weed species that can get established in vinasse amended soils might show higher growth rates.}, number={04}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Soni, N. and Leon, R.G. and Erickson, J.E. and Ferrell, J.A. and Silveira, M.L. and Giurcanu, M.C.}, year={2014}, pages={694–702} }
 @article{murillo castillo_piedra marin_leon_2013, title={Absorcion de nutrientes a traves de la hoja}, volume={27}, journal={Uniciencia}, author={Murillo Castillo, R.G. and Piedra Marin, G. and Leon, R.G.}, year={2013}, pages={232–244} }
 @article{prostko_webster_marshall_leon_grey_ferrell_dotray_jordan_grichar_brecke_et al._2013, title={Glufosinate application timing and rate affect peanut yield response}, volume={40}, DOI={10.3146/ps13-4.1}, abstractNote={ABSTRACT
               Field studies were conducted at 13 locations across the US peanut belt during 2010–2012 to evaluate peanut response to postemergence applications of glufosinate. Glufosinate was applied at 0, 41, 82, 164, 328 and 656 g ai/ha 30, 60, and 90 days after planting (DAP). There was a significant interaction for peanut yield between application time and glufosinate rate; peanut yield data were regressed on rate of glufosinate and fit to a log-logistic dose response curve by application timing. At 30 DAP, peanut yield ranged from 16 to 92% of the non-treated control, with glufosinate at 266 g/ha causing an estimated 50% reduction in yield (Y50). At 60 DAP, peanut yield ranged from 16 to 82% of the nontreated control, with Y50  =  266 g/ha of glufosinate. Peanut yield when glufosinate was applied at 90 DAP ranged from 20 to 78% of the non-treated control; Y50  =  187 g/ha of glufosinate, which was lower than that at 30 DAP and indicated greater peanut sensitivity. Peanut plants treated at 30 DAP had more time to recover from glufosinate injury at the lower rates and/or were in a less susceptible stage of growth relative to 90 DAP. These data provide peanut growers across the US with an estimate of potential yield losses associated with mis-application, off-target movement, or sprayer contamination of glufosinate.}, number={2}, journal={Peanut Science}, publisher={American Peanut Research and Education Society}, author={Prostko, E.C. and Webster, T.M. and Marshall, M.W. and Leon, R.G. and Grey, T.L. and Ferrell, J.A. and Dotray, P.A. and Jordan, D.L. and Grichar, W.J. and Brecke, B.J. and et al.}, year={2013}, pages={115–119} }
 @article{ferrell_leon_sellers_rowland_brecke_2013, title={Influence of lactofen and 2,4-DB combinations on peanut injury and yield}, volume={40}, DOI={10.3146/ps12-15r3.1}, abstractNote={ABSTRACT
               Lactofen plus crop oil adjuvants are increasingly being used to combat acetolactate synthase-resistant weeds in peanut production. To control a broader spectrum of weeds, it is desirable to mix 2,4-DB with lactofen. However, lactofen can be highly injurious to peanuts. It is unknown if the addition of 2,4-DB will exacerbate or prolong the injury observed by lactofen. Experiments were conducted in Citra and Jay, FL in 2011 and 2012 to examine the impact of lactofen, 2,4-DB and lactofen + 2,4-DB applied at 15, 30, and 45 days after planting (DAP) on peanut injury and yield. It was observed that 2,4-DB did not increase foliar injury or stunting (as measured by canopy width) compared to lactofen alone. Additionally, yield was not impacted by any herbicide combination or application timing. From these data, lactofen plus 2,4-DB combinations, applied with crop oil adjuvants, can be used with little concern for exacerbating effects on peanut growth or yield relative to lactofen applied alone.}, number={1}, journal={Peanut Science}, publisher={American Peanut Research and Education Society}, author={Ferrell, J.A. and Leon, R.G. and Sellers, B. and Rowland, D. and Brecke, B.}, year={2013}, pages={62–65} }
 @article{richardson_kellon_leon_arvai_2013, title={Using choice experiments to understand household tradeoffs regarding pineapple production and environmental management in Costa Rica}, volume={127}, DOI={10.1016/j.jenvman.2013.05.043}, abstractNote={Choices among environmental management alternatives involve tradeoffs where, for example, the benefits of environmental protection may be offset by economic costs or welfare losses to individual agents. Understanding individual or household-level preferences regarding these tradeoffs is not always straightforward, and it often requires an analysis of choices under alternative scenarios. A household survey was used to gather data for a choice experiment, where respondents were asked to choose among pairs of alternative management scenarios about pineapple production in Costa Rica. The experimental design consisted of six attributes that varied on between two and five attribute levels, and the experiment and accompanying survey were administered orally in Spanish. The results show that respondents are willing to make tradeoffs with respect to the management attributes in order to see an overall improvement in environmental quality. Respondents were willing to accept a moderate level of pesticide application, presumably in exchange for paying a lower cost or seeing a gain in another area, such as monitoring or soil conservation. Buffer zones were significant only in the case of large farms. The results have implications for policy decisions that aim to reflect public attitudes, particularly the aspects of pineapple production that matter most to people living near pineapple plantations. The study also highlights the effectiveness of the choice experiment approach in examining household preferences about environmental management in a rural development context.}, journal={Journal of Environmental Management}, publisher={Elsevier BV}, author={Richardson, R.B. and Kellon, D. and Leon, R.G. and Arvai, J.}, year={2013}, pages={308–316} }
 @article{leon_kellon_2012, title={Characterization of ‘MD-2' pineapple planting density and fertilization using a grower survey}, volume={22}, DOI={10.21273/horttech.22.5.644}, abstractNote={‘MD-2’ is the predominant pineapple (Ananas comosus) cultivar for fresh fruit export worldwide. Costa Rica is one of the most important producers and exporters of ‘MD-2’, and many growers in this country have switched to this crop. However, growers have expressed concerns about the limited technical information available about how to grow this cultivar. We conducted a survey to gather information about the production practices implemented by commercial pineapple growers in Costa Rica and use this information to describe the response of the crop to these practices. Planting density was the most limiting factor affecting yield. Average planting density was 62,594 plants/ha although planting densities above 70,000 plants/ha produced highest yields. Average yields were 7130 and 4723 boxes/ha for the mother plant and ratoon crops, respectively. Fruit weight ranged from 1.5 to 2.0 kg and was not evidently affected by planting density or fertilization. Fertilization levels were between 632 and 520 kg·ha−1 nitrogen (N), 129 and 93 kg·ha−1 phosphorous (P), and 400 and 340 kg·ha−1 potassium for the mother plant and ratoon crops, respectively. In focus groups, growers considered that N and P levels could be reduced by 20% and 66% respectively, without jeopardizing yield. Results indicated that management practices must be modified for the ratoon crop to avoid yield reductions. The present study illustrated how a collaborative effort in which growers share information about their production practices can generate valuable data needed to identify adequate practices when funding and technical support are not available to experimentally generate these type of data.}, journal={HortTechnology}, publisher={American Society for Horticultural Science}, author={Leon, R.G. and Kellon, D.}, year={2012}, pages={644–650} }
 @article{mauaie_leon_2012, title={Evaluacion fisiologica de las propiedades nutritivas del fungicida propineb en banano (Musa spp.)}, volume={8}, journal={Tierra Tropical}, author={Mauaie, V.E. and Leon, R.}, year={2012}, pages={229–235} }
 @article{tuñón_espinoza_leon_2012, title={Evaluación de cultivares de caña energética para producción de biomasa en primera soca}, volume={8}, journal={Tierra Tropical}, author={Tuñón, P.A. and Espinoza, J.L. and Leon, R.}, year={2012}, pages={179–188} }
 @article{leon_gilbert_korndorfer_comstock_2010, title={Selection criteria and performance of energycane clones (Saccharum spp. × S. spontaneum) for biomass production under tropical and sub-tropical conditions}, volume={51}, DOI={10.5377/ceiba.v51i1.641}, abstractNote={The urgent need to reduce our reliance on oil and at the same time reduce carbon emissions, has triggered the search for alternative energy sources such as biofuels. New technologies have made possible the conversion of cellulose and hemicellulose into sugars that can be fermented to produce ethanol. This opened the possibility that any plant species can be used for ethanol production. Species that produce large amounts of biomass in a short time are desirable. For this reason, one of the most critical steps in the development of biofuel production is to identify appropriate species that will provide the necessary biomass for cellulosic ethanol or direct combustion. Energycanes are wide crosses of commercial sugarcane (a complex hybrid of Saccharum spp.) with S. spontaneum clones which produce high-biomass plants with high fiber content and good cold and disease tolerance as well as excellent ratooning ability. A large scale study has been established to evaluate biomass production, growth characteristics and invasive potential of energycane clones under tropical (Limón, Costa Rica) and subtropical (South Florida) conditions since 2008. In Florida in a low fertility sandy soil, energycane clones and the grass species Pennisetum purpureum var. Merkeron showed the highest yields ranging from 50 to 78 ton ha-1 of fresh weight. These clones were not susceptible to smut (Sporisorium scitaminea) unlike the energycane L79-1002 which is currently the most widely grown clone of energycane. Most clones showed lateral vegetative growth, but no pollen or seed viability. In Costa Rica, the evaluation of 15 energycane clones is still in progress, however preliminary results indicated that the energycane clones had faster and more vigorous growth than the commercial sugarcane varieties, only exceeded by P. purpureum. In comparison with commercial sugarcane varieties, the energycane clones recorded 37% higher leaf area index (LAI) and height, and 65% more stalks per unit area. No evident disease susceptibility was observed in the energycane clones in the tropics, although lateral vegetative growth was observed in all clones. Additionally, all clones flowered and produced viable pollen which suggests that these clones have a higher invasive potential in the tropics. The information available until now suggests that the behavior of energycane germplasm varies importantly between tropical and sub-tropical conditions. Therefore, selection and breeding programs must be carefully developed accounting for the unique responses that this germplasm could show under these two different climatic conditions.}, number={1}, journal={CEIBA}, publisher={Latin America Journals Online}, author={Leon, R.G. and Gilbert, R.A. and Korndorfer, P.H. and Comstock, J.C.}, year={2010}, pages={11–16} }
 @article{ramos_vaquero_leon_ayuso_2011, title={Efecto de tres especies de cobertura viva en el control de malezas en una plantacion de banano organico (Musa AAA cv Williams)}, volume={7}, journal={Tierra Tropical}, author={Ramos, O. and Vaquero, R. and Leon, R. and Ayuso, F.}, year={2011}, pages={1–10} }
 @article{sanguankeo_leon_2011, title={Weed management practices determine plant and arthropod diversity and seed predation in vineyards}, volume={51}, DOI={10.1111/j.1365-3180.2011.00853.x}, abstractNote={Sanguankeo PP & León RG (2011). Weed management practices determine plant and arthropod diversity and seed predation in vineyards. Weed Research51, 404–412.SummaryIn the Central Coast of California, USA, wine grape growers are making efforts to identify weed control practices that preserve biodiversity in their vineyards while maintaining yields. A field study was conducted in Paso Robles, California in 2006 and 2007 evaluating the effect on plant and ground dwelling arthropod communities of five weed control practices conducted under the vines within the row (berm): (i) flumioxazin, (ii) simazine, (iii) cultivation, (iv) cover crop and (v) untreated control. The cover crop, cultivation and untreated control had 4–50 times higher plant density and more than 15 times higher plant diversity compared with the herbicide treatments. The arthropod activity‐density differed among treatments only in 2007, being higher in the cover crop and untreated control. There was a positive relationship between plant and arthropod diversity (r2 = 0.42, P = 0.02 in 2006; r2 = 0.64, P < 0.001 in 2007). Laboratory seed predation tests of the two most frequently captured carabid beetles, Calathus ruficollis and Tanystoma maculicolle, indicated they predated more of the common weed species Brassica nigra and Capsella bursa‐pastoris, than other weed species tested. Under field conditions, treatments with higher plant diversity and density favoured arthropod seed predation of these weeds. Predation rates were 20–40% in the cover crop and untreated control, double that observed in the herbicide treatments. The cultivation treatment balanced the benefits of promoting diversity while minimising yield reductions caused by weed competition. The results indicate that weed management practices that promote higher plant diversity and density have the potential to yield ecological benefits within vineyards, for example, enhancing the activity of beneficial organisms.}, number={4}, journal={Weed Research}, publisher={Wiley}, author={Sanguankeo, P.P. and Leon, R.G.}, year={2011}, pages={404–412} }
 @article{zafra_condori_leon_ulloa_2010, title={Efecto de la intensidad de la labranza sobre las caracteristicas del suelo y la produccion de maiz}, volume={6}, journal={Tierra Tropical}, author={Zafra, G. and Condori, G. and Leon, R. and Ulloa, O.}, year={2010}, pages={79–86} }
 @article{morgan_gilbert_helsel_baucum_leon_perret_2010, title={White paper report from working groups attending the international conference on research and educational opportunities in bio-fuel crop production}, volume={34}, DOI={10.1016/j.biombioe.2010.07.004}, abstractNote={A conference on current research and educational programs in production of crops for bio-fuel was sponsored and organized by the EARTH University and the University of Florida in November, 2008. The meeting addressed current research on crops for bio-fuel production with discussions of research alternatives for future crop production systems, land use issues, ethics of food vs. fuel production, and carbon sequestration in environmentally sensitive tropical and sub-tropical regions of the Americas. The need and potential for development of graduate and undergraduate curricula and inter-institutional cooperation among educational institutions in the region were also discussed. Delegations from Belize, Brazil, Columbia, Costa Rica, Cuba, Honduras, Panama, The Dominican Republic, and the United States including ministers of Agriculture and Energy attended this meeting. Over a two-day period, four working groups provided a framework to facilitate networking, motivate task oriented creative thinking, and maintain a timely accomplishment of assigned duties in the context of the conference themes. Participants in the conference were assigned to one of four working groups, each following given topics: Agronomy, Environment, Socio-Economics and Education/Extension. It was the consensus of representatives of industry, academic and regulatory community assembled in Costa Rica that significant research, education and socio-economic information is needed to make production of bio-fuel crops sustainable. Agronomic research should include better crop selection based on local conditions, improved production techniques, pest and disease management, and mechanical cultivation and harvesting. Another conclusion was that tailoring of production systems to local soil characteristics and use of bio-fuel by-products to improve nutrient use efficiency and reduction of environmental impact on water quantity and quality is critical to sustainability of bio-fuel crop production.}, number={12}, journal={Biomass and Bioenergy}, publisher={Elsevier BV}, author={Morgan, K.T. and Gilbert, R.A. and Helsel, Z.A. and Baucum, L. and Leon, R. and Perret, J.}, year={2010}, pages={1968–1972} }
 @article{laforest_vedia_leon_2009, title={Alternativas de control para el manejo de malezas en banano organico en establecimiento}, volume={5}, journal={Tierra Tropical}, author={Laforest, S. and Vedia, M. and Leon, R.}, year={2009}, pages={225–235} }
 @article{sanguankeo_leon_malone_2009, title={Impact of weed management practices on grapevine growth and yield components}, volume={57}, DOI={10.1614/ws-08-100.1}, abstractNote={The need for reducing costs and making grape production more sustainable has prompted the search for alternative weed control practices that optimize production while maintaining profits. For this reason, it is imperative to understand how different weed management practices modify vine–weed interactions. In the present study, we evaluated the effect on weed growth and Zinfandel grapevine growth and production of five weed control practices: (1) flumioxazin, (2) simazine, (3) cultivation, (4) cover crop, and (5) untreated control. The herbicide treatments had the lowest weed biomass, followed by the cultivation, being approximately 10 and 2 times lower than the weed biomass of either the cover crop or untreated control treatments, respectively. However, the differences in grape yield were not as evident. In 2006, a rainy year, the herbicides and cultivation treatments did not differ in grape yield, but the cover crop and untreated control had a reduction of approximately 20% compared with the other treatments. In 2007, a dry year, in comparison to the herbicide treatments, the grape yield reductions of cultivation were around 22%, and those of the cover crop and untreated control were around 48%. Although the cover crop reduced grape yield, it suppressed weed species considered important, such as horseweed, panicle willowherb, scarlet pimpernel, and sowthistle. Also, it was concluded that vines can tolerate a certain amount of weed competition, and that properly timed postemergence control actions (e.g., cultivation or POST herbicides) could provide the necessary level of control to obtain the desired yields. However, under limited soil moisture conditions, the use of PRE herbicides could prove important to maintain vine yield and vigor.}, number={01}, journal={Weed Science}, publisher={Cambridge University Press (CUP)}, author={Sanguankeo, P.P. and Leon, R.G. and Malone, J.}, year={2009}, pages={103–107} }
 @article{leon_ferreira_2008, title={Interspecific differences in weed susceptibility to steam injury}, volume={22}, DOI={10.1614/wt-07-150.1}, abstractNote={Thermal weed control methods have been incorporated into weed control programs in organic and conventional production systems. Flaming is commonly used, but steaming has been proposed to increase efficiency of heat transfer to weeds and reduce the risk of fire. The objective of this research was to measure injury to leaves of plant species that differ in leaf morphology and to measure injury to plants at different stages of plant development. The study was conducted in a glasshouse and plants were exposed to steaming at 400 C for 0.36 s—equivalent to a steaming speed of 2 km/h. Overall, leaf thickness was the best morphological characteristic to predict injury (r2 = 0.51), with greater thickness resulting in less injury. For broadleaf species only, species with wider leaves were injured more than species with narrower leaves (r2 = 0.64). Injury was greatest when plants had fewer than six true leaves and when their shoots were less than 10 cm long. There was a wide range of injury across species, and the grass species bermudagrass and perennial ryegrass were injured (68 to 81%) more than other species such as common purslane and English daisy (23 to 34%). Biomass of all species tested was reduced by approximately 40%, indicating that leaf injury was not the sole effect of steaming on plant growth. These results indicated that considering both visual estimates of injury and morphological characteristics is important to properly assess thermal weed control effectiveness.}, number={04}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Ferreira, D.T.}, year={2008}, pages={719–723} }
 @article{leon_bassham_owen_2007, title={Thermal and hormonal regulation of the dormancy-germination transition in Amaranthus tuberculatus seeds}, volume={47}, DOI={10.1111/j.1365-3180.2007.00571.x}, abstractNote={SummaryThe transition from seed dormancy to germination is a multi‐step process. However, distinguishing between physiological processes involved in seed dormancy alleviation and those involved in germination has been difficult. We studied the seed dormancy alleviation process in Amaranthus tuberculatus, an important weed species in midwestern USA. Using three A. tuberculatus biotypes that differ in dormancy level, it was determined that stratification reduced seed dormancy from a high to a low level. Temperature alternation alleviated low seed dormancy and triggered germination. Exogenously applied abscisic acid (ABA) and gibberellic acid (GA) had no effect on seeds with high dormancy. However, ABA and paclobutrazol (a GA biosynthesis inhibitor) significantly reduced germination of seeds with low dormancy. Hormones could not replace the effects of stratification or temperature alternation on dormancy alleviation. Based on our results, we propose a seed dormancy–germination transition model in which the dormancy of A. tuberculatus seeds is progressively reduced from a high to a low level; but environmental conditions (i.e. stratification) can accelerate the dormancy alleviation process. Under low dormancy levels, the seed is more sensitive to environmental cues that are responsible for removing dormancy and triggering germination (i.e. temperature alternation). Finally, ABA and GA regulation occurs primarily during the final transition from low dormancy to germination rather than the alleviation of high dormancy.}, number={4}, journal={Weed Research}, publisher={Wiley}, author={Leon, R.G. and Bassham, D. and Owen, M.D.K.}, year={2007}, pages={335–344} }
 @article{leon_aguero_2001, title={Efecto de distintos tipos de labranza sobre la población de malezas en el Agroecosistema de la caña de azúcar (Saccharum officinarum L.)}, volume={12}, DOI={10.15517/am.v12i1.17289}, abstractNote={Experiments were conducted in two sugarcane fields, one with low weed pressure (plot 1) and the other with high weed pressure (plot 2). Four treatments were established in each study: green harvest that left plant mulch on soil surface (VCR), green harvest without plant mulch on soil surface (VSR), burning the crop before harvest without soil disturbance (QSL) and burning the crop before harvest with soil disturbance (QCL). Evaluations were made 75 days after harvest. The evaluations were conducted separately in rows and between rows. In addition, sugarcane population and height were measured. Differences in weed populations were not observed for the field with low weed pressure (plot 1). In the field with high weed pressure (plot 2), weeds were favored by burning and soil disturbance caused by fertilizer incorporation. Thus the treatments QSL and QCL showed the highest percentage of surface coverage. Also, the QCL treatment had the greatest weed populations resulting in reduced sugarcane population and height. Purple nutsedge (Cyperus rotundus L.) and itchgrass (Rottboellia cochinchinensis (Lour.) Clayton) had the greatest percentage surface coverage, especially in QCL. Weed populations were larger in rows than between rows. Apparently in rows, weeds found better conditions for germination and nutrient uptake.}, number={1}, journal={Agronomía Mesoamericana}, publisher={Universidad de Costa Rica}, author={Leon, R. and Aguero, R.}, year={2001}, pages={71–77} }
 @article{leon_aguero_2001, title={Efecto de la profundidad del suelo sobre el establecimiento de plantas de Rottboellia cochinchinensis (Lour.) Clayton en el Agroecosistema de la caña de azúcar (Saccharum officinarum L.)}, volume={12}, DOI={10.15517/am.v12i1.17288}, abstractNote={Four sugarcane fields with different soil textures (clay loam, sandy loam, clay and loam) were sampled. All fields showed R. cochinchinensis populations with at least 75-150 plants/m2. The number of plants of this weed in 0.25 m2 was determined separately in the microhabitats: rows and between rows. The depth at which each plant emerged was measured. Based on depth emergence, each plant was distributed in one of the next categories: 0, >0-2.5, >2.5-5.0, >5.0-10 and >10.0-15.0 cm. In addition, under greenhouse conditions, seeds were seeded in pots at the maximum depth of each category in order to evaluate the effect of soil depth. Finally, the effect of light and darkness on seed germination were evaluated in Petri dishes under laboratory conditions. In the field evaluations most of the plants emerged from >0-2.5 cm. The second most common category was >2.5-5.0 cm. It seems that those depths provide optimum conditions for germination. There were no differences regarding soil texture or microhabitats. In the greenhouse experiment, the largest germination was observed at 0 cm due to light exposure in this treatment. This was confirmed in the laboratory where light treatment showed also the largest germination. Control strategies that keep the seeds of this species above ground will reduce the number of new seeds in the seed bank and avoid optimum field conditions for its germination. If such strategies include efforts to reduce the seed production of those plants that are able to become established, it could be possible to significantly reduce the seed bank, therefore, it would be easier to control the population of this weed.}, number={1}, journal={Agronomía Mesoamericana}, publisher={Universidad de Costa Rica}, author={Leon, R. and Aguero, R.}, year={2001}, pages={65–69} }
 @article{leon_bassham_owen_2006, title={Germination and proteome analyses reveal intra-specific genetic variation in seed dormancy regulation of common waterhemp (Amaranthus tuberculatus)}, volume={54}, DOI={10.1614/ws-05-115r1.1}, abstractNote={Common waterhemp is an obligate outcrosser that has high genetic variability. However, under selection pressure, this weed shows population differentiation for adaptive traits. Intraspecific variation for herbicide resistance has been studied, but no studies have been conducted to determine the existence of variation for other adaptive traits that could influence weed management. The objective of this study was to examine the existence of different seed dormancy regulatory mechanisms in common waterhemp. Seed dormancy regulation, in response to different temperature and moisture regimes, was studied through germination experiments and proteome analysis using two common waterhemp biotypes (Ames and Everly) collected from agricultural fields in Iowa, and one biotype (Ohio) collected from a pristine area in Ohio. Without stratification, germination percentage among the different biotypes was 9, 29 and 88% for Ames, Everly, and Ohio respectively. The germination rate of seeds from Ames was dramatically increased after incubation at either 4 or 25 C under wet conditions, whereas germination of seeds from Everly was only increased at 25 C under wet conditions. The Ohio biotype showed no change in germination response to any of the incubation treatments. Germination studies indicated that the rate of seed dormancy alleviation differed between biotypes. Seed protein profiles obtained from the three biotypes differed in protein abundance, number, and type. A putative small heat-shock protein (sHSP) of 17.6 kDa and isoelectric point (pI) 6.1 increased whereas a putative glyceraldehyde-3-phosphate dehydrogenase (G3PDH) of 30.9 kDa and pI 6.4 decreased in abundance in the Ames biotype as seed dormancy was reduced in response to incubation at 4 C and wet conditions. These two proteins did not change in the Everly and Ohio biotypes, suggesting that these proteins changed their abundance in response to seed dormancy alleviation. The results of this study suggest that differences in seed dormancy levels between the biotypes were due to different physiological regulatory mechanisms.}, number={02}, journal={Weed Science}, publisher={Weed Science Society}, author={Leon, R.G. and Bassham, D. and Owen, M.D.K.}, year={2006}, pages={305–315} }
 @article{leon_bassham_owen_2006, title={Inheritance of deep seed dormancy and stratification-mediated dormancy alleviation in Amaranthus tuberculatus}, volume={16}, DOI={10.1079/ssr2006250}, abstractNote={Amaranthus tuberculatusis a weed species that has shifted emergence patterns over the past few years, presumably due to changes in seed dormancy in response to selection in agricultural fields. Although it is recognized that the seed dormancy phenotype is greatly affected by the environment, it is also acknowledged that the genotype plays a significant role. However, the importance of the genotype in determining intra-population seed dormancy variability, and the effect on emergence patterns, is not well understood. The objective of the present study was to determine the importance of the genotype on deep dormancy and the stratification-mediated dormancy alleviation inA. tuberculatus. Wild populations differing in seed dormancy were crossed and F2families were generated. These families were used to determine narrow sense heritability of dormancy and stratification-mediated dormancy alleviation at the individual (hi2) and family (hf2) levels.hi2ranged from 0.13 to 0.4 and 0.04 to 0.06 for the dormancy and stratification response, respectively. In the case ofhf2, the values ranged from 0.76 to 0.91 for deep dormancy and from 0.33 to 0.58 for the stratification response. The genetic correlation between these two traits was below 0.075, indicating that different genes control them. High temperature strengthened the dormancy of deeply dormant seeds, making them less sensitive to stratification. However, high temperature promoted the germination of non-deeply dormant seeds. It is proposed that delayed weed emergence can be generated by selecting genes that control stratification response, and not necessarily only the genes that are directly responsible for deep dormancy.}, number={03}, journal={Seed Science Research}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Bassham, D. and Owen, M.D.K.}, year={2006}, pages={193–202} }
 @article{leon_owen_2006, title={Tillage systems and seed dormancy effects on common waterhemp (Amaranthus tuberculatus) seedling emergence}, volume={54}, DOI={10.1614/ws-06-009.1}, abstractNote={Abstract Understanding weed seedling emergence patterns is important for successful implementation of many weed management strategies. Identifying the sources of variation of emergence patterns could greatly improve our ability to predict emergence timing. Differences in seed dormancy levels between populations or biotypes are usually not considered when studying seedling emergence of many weed species despite evidence that dormancy levels can affect weed seedling emergence patterns. We studied the importance of seed dormancy on seedling emergence patterns of common waterhemp using three biotypes (Ames, Everly, and Ohio) that differed in dormancy regulation and level (5, 26, and 87% germination, respectively) and three tillage systems (no-tillage, chisel plow, and moldboard plow) in 2004 and 2005. Seedling emergence was at least four times greater under no-tillage than under chisel or moldboard plow conditions. Fewer seedlings emerged in moldboard plow than in other tillage systems. Furthermore, seedling emergence occurred in no-tillage over a longer period than in chisel and moldboard plow. In no-tillage the largest emergence events occurred at the end of June, whereas in other tillage systems most emergence occurred during May and the first week of June. Among biotypes, differences in number of emerged seedlings were more evident than differences in emergence timing. For Everly and Ohio biotypes, the number of emerged seedlings was the same between chisel and moldboard plow plots. For the Ames biotype, in 2004, the number of emerged seedlings was 25-fold higher in chisel plow than in moldboard plow, and the emergence pattern in no-tillage was longer and peaked later than in the other tillage systems. However, these results were not observed in 2005. Overall, we did not observe consistent differences in seedling emergence patterns among biotypes, which suggested that under field conditions, other factors can compensate for differences in seed dormancy levels. Nomenclature: Common waterhemp, Amaranthus tuberculatus (Moq.) Sauer.}, number={6}, journal={Weed Science}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Owen, M.D.K.}, year={2006}, pages={1037–1044} }
 @article{leon_owen_soh_tylka_2005, title={Absence of interactive responses of early soybean (Glycine max) growth to soybean cyst nematode (Heterodera glycines), post-emergence herbicides and soil pH and texture}, volume={19}, DOI={10.1614/wt-03-149r1.1}, abstractNote={Farmer observations and previous studies indicated that reductions in soybean yield caused by the soybean cyst nematode (SCN) are greater when other stresses, biotic or abiotic, are present. Also, it has been reported that the effect of SCN on soybean growth depended on factors such as soil pH, soil texture, and herbicides. Although postemergence herbicides may adversely affect soybean metabolism, acifluorfen can reduce SCN infection. The objective of the present study was to determine the main and interactive effects of SCN egg population density (SCND), soil pH, soil texture, and the application of the herbicides acifluorfen, glyphosate, and imazethapyr on early soybean growth. Greenhouse studies assessed different combinations of these factors for 65 d after planting. No interactions were observed for any of the main effects. Soil pH and texture did not affect soybean growth. SCND was the only main effect that explained soybean growth reductions. The effect of SCND on soybean growth was exhibited as 15–50% decreases of leaf area index (LAI) and dry weight in all cases, but reductions in plant height also were observed. No relationship between SCND and the number of SCN eggs recovered at the end of the experiment was observed. Herbicides did not reduce soybean growth, although acifluorfen consistently caused the highest soybean injury reaching 18–20% from 1–14 days after application (DAA). At 50 DAA, acifluorfen injury was negligible, and soybean LAI and dry weight did not differ from the nontreated control. These results indicated that the effect of SCN on soybean growth was not directly affected by the other evaluated main effects. Therefore, trends observed in the field that suggested interactions between those factors are likely the result of other factors not considered in the present study or to more complex relationships between factors analyzed in the present study and other elements present in the field. Nomenclature: Acifluorfen, glyphosate, imazethapyr; soybean; soybean cyst nematode, Heterodera glycines Ichinoche. Additional index words: Herbicide injury, nematode infection. Abbreviations: AMS, ammonium sulfate; COC, crop oil concentrate; DAA, days after application; DAP, days after planting; LAI, leaf area index: MSO, methylated seed oil; PPFD, photosynthetic photon flux density; SCN, soybean cyst nematode; SCND, SCN egg population density.}, number={4}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Owen, M.D.K. and Soh, D. and Tylka, G.}, year={2005}, pages={847–854} }
 @article{leon_owen_2004, title={Artificial and natural seed banks differ in seedling emergence patterns}, volume={52}, DOI={10.1614/ws-03-048r2}, abstractNote={Artificial weed seed banks are practical for studying seed bank depletion and weed seedling emergence because the number, depth, and species composition of seed banks can be managed. However, no studies have determined whether artificial seed banks are representative of natural seed banks. We compared the emergence of velvetleaf, giant foxtail, and common waterhemp in a natural seed bank, an artificial seed bank with stratified seeds, and an artificial seed bank with nonstratified seeds. Velvetleaf seedling emergence was higher in the nonstratified seed bank in 2001, but no differences were observed in 2002. The number of viable velvetleaf seeds at the end of the experiment was lower in the natural seed bank than in the artificial seed banks in 2002. Velvetleaf emergence occurred earlier in the natural seed bank than in the artificial seed banks. Giant foxtail emergence was higher in the artificial seed banks (58 to 82%) than in the natural seed bank (5 to 23%). Common waterhemp emergence ranged from 7 to 65% in the artificial seed banks and from 1 to 5% in the natural seed bank. In general, the distribution of emergence with time differed in the natural seed bank compared with the artificial seed banks. These differences were attributed to differences in soil temperature and soil bulk density between the natural and artificial seed banks. Artificial seed banks showed lower soil bulk density and greater temperature fluctuation than the natural seed bank. However, there was no consistent relationship between growing degree days and emergence timing in the three treatments for any of the species studied.}, number={04}, journal={Weed Science}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Owen, M.K.D.}, year={2004}, pages={531–537} }
 @article{leon_knapp_owen_2004, title={Effect of temperature on the germination of common waterhemp (Amaranthus tuberculatus), giant foxtail (Setaria faberi), and velvetleaf (Abutilon theophrasti)}, volume={52}, DOI={10.1614/p2002-172}, abstractNote={Common waterhemp, giant foxtail, and velvetleaf seed germination in response to temperature was studied with a two-way thermogradient plate. Seeds were maintained under dark and wet conditions at 4 C for 12 wk, and velvetleaf seeds were scarified before the experiments were conducted. The seeds were germinated at 25 different temperature treatments. Minimum and optimum temperatures for velvetleaf germination were approximately 8 and 24 C, respectively. Temperature alternation did not affect the germination of this species. The minimum germination temperature was 10 C for common waterhemp and 14 C for giant foxtail. The optimum germination of giant foxtail occurred at approximately 24 C, but common waterhemp optimum germination was variable depending on temperature alternation. Increased amplitude of the diurnal temperature alternation increased percent germination of these two species, and this was more evident at lower temperatures. In the case of common waterhemp, the temperature required to reach specific germination percentages was reduced by increasing the amplitude of the temperature alternation.}, number={01}, journal={Weed Science}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Knapp, A.D. and Owen, M.D.K.}, year={2004}, pages={67–73} }
 @article{leon_owen_2003, title={Regulation of weed seed dormancy through light and temperature interactions}, volume={51}, DOI={10.1614/p2002-173}, abstractNote={Abstract The effects of temperature and light on the dormancy of velvetleaf, common waterhemp, and giant foxtail seeds were studied under controlled growth chamber conditions. Seeds were either kept chilled at 4 C for 12 wk under wet conditions or nonchilled at 4 C in dry storage. Then, seeds were germinated under increasing and decreasing temperatures and under continuous red light (R) and far-red light (FR). In addition, chilled and nonchilled seeds were germinated in the dark after being exposed to alternating R and FR flashes. Velvetleaf germination was increased by exposure to high temperatures (36 C) immediately after exposure to low temperatures (4 C), but light had no effect. Chilling increased common waterhemp seed germination and sensitivity to light and temperature. R promoted common waterhemp seed germination, whereas FR inhibited germination and maintained dormancy. In addition, the effect of light was reversible. Therefore, common waterhemp dormancy was phytochrome regulated. However, high temperatures (36 C) promoted the germination of chilled seeds, even when exposed to FR. The germination of chilled giant foxtail seeds was reduced by FR. Giant foxtail seed dormancy was partially phytochrome regulated, but dormancy regulation was more dependent on mean temperature. Nomenclature: Common waterhemp, Amaranthus tuberculatus (Moq.) J.D. Sauer. syn. Amaranthus rudis Sauer. AMATA; giant foxtail, Setaria faberi Herrm. SETFA; velvetleaf, Abutilon theophrasti Medicus. ABUTH.}, number={5}, journal={Weed Science}, publisher={Cambridge University Press (CUP)}, author={Leon, R.G. and Owen, M.D.K.}, year={2003}, pages={752–758} }