@article{volk_jennings_fennimore_hoffmann_2023, title={Preplant Application of Allyl Isothiocyanate Controls Weeds and Pathogens in Eastern North Carolina Strawberry (Fragaria xananassa cv. Camarosa) with and without Addition of Soil-applied Steam}, volume={58}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI17321-23}, abstractNote={Allyl isothiocyanate (AITC) is a colorless aliphatic oil that naturally occurs in many plants of the cabbage and mustard family (Brassicaceae). It has antimicrobial activity and is used as pesticide for a variety of applications. However, AITC as a soil disinfectant has exhibited inconsistent weed and pathogen control, mainly because of its higher viscosity and low vapor pressure (5 mmHg at 25 °C). Steam, however, effectively controls soil-borne pathogens if soil temperatures of 65 °C or more are reached for a minimum duration of 30 minutes. We hypothesized that steam applications targeting lower temperatures, when combined with soil-injected AITC, will provide sufficient weed and pathogen control. We further hypothesized that the combination of AITC and steam will lead to higher strawberry yields compared with either of the components on their own. Two strawberry (Fragaria ×ananassa cv. Camarosa) trials were conducted during two consecutive seasons (2020–21 and 2021–22). The trials were conducted at the Central Crops Research Station in Clayton, NC, USA, and the Horticulture Research Station in Castle Hayne, NC, USA. Eight treatments and a nontreated control were established in a randomized complete block design (four replicates each). The treatments were Pic-Clor 60, AITC, AITC followed by 60 minutes of steam injection, AITC followed by 30 minutes of steam injection, AITC followed by 10 minutes of steam injection, 60 minutes of steam injection, 30 minutes of steam injection, and 10 minutes of steam injection. Soilborne pathogen control efficacy was assessed using wet Pythium sp. plating assays. Weed control was assessed through weed seed/tuber germination assays. Our results showed that combining ATIC with steam did not reduce weed or pathogen levels or improve yield when compared with AITC alone or Pic-Clor 60. Moreover, treatment comprising steam alone did not provide sufficient control. However, AITC alone controlled weeds and pathogens as effectively as Pic-Clor 60 during both years and both locations of the study. These results showed that AITC alone could be a potential alternative soil disinfectant for Eastern North Carolina strawberry production.}, number={10}, journal={HORTSCIENCE}, author={Volk, Emma and Jennings, Katie and Fennimore, Steven F. and Hoffmann, Mark}, year={2023}, month={Oct}, pages={1242-+} }
 @article{sims_mitchem_jennings_monks_jordan_hoffmann_2023, title={Tolerance of muscadine grape to 2,4-D choline postemergence-directed}, volume={2}, ISSN={["1550-2740"]}, DOI={10.1017/wet.2023.8}, abstractNote={Abstract}, journal={WEED TECHNOLOGY}, author={Sims, Kira C. and Mitchem, Wayne E. and Jennings, Katherine M. and Monks, David W. and Jordan, David L. and Hoffmann, Mark}, year={2023}, month={Feb} }
 @article{freedman_rana_hoffmann_2022, title={Phenology Based Variability of Tissue Nutrient Content in Mature Muscadine Vines (Vitis rotundifolia cv. Carlos)}, volume={12}, ISSN={["2077-0472"]}, DOI={10.3390/agriculture12111805}, abstractNote={Muscadine (Vitis rotundifolia) is a grape species that is native to the Southeastern US, where several cultivars are grown commercially for processing or direct consumption. Phenology based tissue analysis to determine the nutritional status of a vine is a critical tool for growers to understand fertilizer demands in a vineyard. For European-style wine grapes, tissue sampling for nutrient content is well researched. However, current tissue sampling recommendations for muscadines are solely based on anecdotal knowledge. It is currently unknown if the type of tissue collected has an impact on variability and content of nutrients. Questions also remain as to whether or not seasonal vine phenology impacts tissue nutrient content. Without this knowledge it is difficult for a muscadine grower to make informed decisions on the nutritional status of a muscadine vine. Therefore, we investigated the impact of the phenological vine stage (bloom, fruit set, véraison) on nutrient content in two different tissue types (mature leaf vs. petiole), sampled at two different positions on a muscadine vine (opposite of cluster vs. shoot). The study was conducted over two growing seasons (2019 and 2020) in a commercial mature muscadine vineyard (‘Carlos’). Our results show that over both study years, the highest variability in nutrient content was found during bloom (May–June), while nutrient variability was lower during fruit-set and veraison. We also found fully mature leaf samples showed a lower variability in nutrient tissue content. Based on our results, sampling fully mature leafs from shoots remains the best practice. However, our results also indicate that tissue sampling later in the season might be a better practice, compared to the current practice of taking samples during June.}, number={11}, journal={AGRICULTURE-BASEL}, author={Freedman, Kyle Austin and Rana, Tekan Singh and Hoffmann, Mark}, year={2022}, month={Nov} }
 @article{sims_jennings_monks_jordan_hoffmann_mitchem_2022, title={Tolerance of plasticulture strawberry to 2,4-D choline applied to row middles}, volume={4}, ISSN={["1550-2740"]}, DOI={10.1017/wet.2022.27}, abstractNote={Abstract}, journal={WEED TECHNOLOGY}, author={Sims, Kira C. and Jennings, Katherine M. and Monks, David W. and Jordan, David L. and Hoffmann, Mark and Mitchem, Wayne E.}, year={2022}, month={Apr} }
 @article{sims_jennings_monks_mitchem_jordan_hoffmann_2022, title={Tolerance of southern highbush blueberry to 2,4-D choline postemergence-directed}, volume={4}, ISSN={["1550-2740"]}, DOI={10.1017/wet.2022.33}, abstractNote={Abstract}, journal={WEED TECHNOLOGY}, author={Sims, Kira C. and Jennings, Katherine M. and Monks, David W. and Mitchem, Wayne E. and Jordan, David L. and Hoffmann, Mark}, year={2022}, month={Apr} }
 @article{hoffmann_talton_nita_jones_al rwahnih_sudarshana_almeyda_2021, title={First report of grapevine leafroll-associated virus 3 in Vitis vinifera in North Carolina}, volume={103}, ISSN={["2239-7264"]}, DOI={10.1007/s42161-020-00710-3}, number={1}, journal={JOURNAL OF PLANT PATHOLOGY}, author={Hoffmann, Mark and Talton, Win and Nita, Mizuho and Jones, Taylor and Al Rwahnih, Maher and Sudarshana, Mysore and Almeyda, Christie}, year={2021}, month={Feb}, pages={385–386} }
 @article{shi_hernandez_hoffmann_2021, title={Impact of Nitrate and Ammonium Ratios on Flowering and Asexual Reproduction in the Everbearing Strawberry Cultivar Fragaria x ananassa Albion}, volume={7}, ISSN={["2311-7524"]}, DOI={10.3390/horticulturae7120571}, abstractNote={Ever-bearing (EB) strawberries are long-day cultivars that show perpetual flowering behavior. Compared to June-bearing short-day cultivars, EB cultivars can initiate flowers with less dependency on light and temperature levels. This leads to a more consistent flowering and fruiting pattern, making EB cultivars favorable for areas with long growing seasons. However, this flowering pattern also brings significant challenges to open-field strawberry nurseries. Consistent flower development in EB cultivars frequently leads to increased labor cost for manual flower removal on nursery ground. The alteration of flowering behavior via fertilizer regimes could be a cost-effective tool for strawberry nurseries. However, while it is known that the source of nitrogen (N) impacts strawberry flowering, its effect on strawberry propagation rates needs further investigation. The objective of this study was to investigate the impact of nitrate (NO3−) to ammonium (NH4+) ratio on flower and daughter plant production in the EB strawberry cultivar ‘Albion’ (Fragaria × ananassa c.v. ‘Albion’). Strawberry plants were grown in a completely randomized design under greenhouse conditions (26.6 °C, 16 h photoperiod). Four treatments of NO3−:NH4+ were implemented: (1) 100%:0%; (2) 80%:20%; (3) 60%:40%; (4) 50%:50%. Strawberry plants fertilized with a 60%:40% NO3−:NH4+ ratio produced 17–31% fewer inflorescences than those fertilized with 100%:0% (8.8 ± 1.19) and 80%:20% (10.3 ± 1.85) ratios. The production of daughter plants remained similar in all four treatments. Our results show that increased ratios of ammonium in combination with decreased ratios of nitrate reduce flowering of EB strawberry cultivars, while propagation rates remain consistent. These results could potentially lead to the development of fertilizer regimes for strawberry nurseries to reduce flower production in EB cultivars.}, number={12}, journal={HORTICULTURAE}, author={Shi, Xiaonan and Hernandez, Ricardo and Hoffmann, Mark}, year={2021}, month={Dec} }
 @article{rana_smith_hickey_hoffmann_2021, title={Leaf-tissue Nutrient Dynamics in Mature Muscadine Cultivars Carlos and Noble in Georgia and North Carolina}, volume={31}, ISSN={["1943-7714"]}, DOI={10.21273/HORTTECH04765-20}, abstractNote={More than 3000 acres of commercial muscadine (Vitis rotundifolia) vineyards exist in the southeastern United States. The muscadine wine industry is generating an economic impact of $1 billion in North Carolina alone. Muscadines have been cultivated since the 1800s, but muscadine vineyard fertilizer programs, tissue sampling, and nutrient sufficiency ranges continue to be based on anecdotal knowledge. While seasonal changes in tissue nutrient concentration are well documented in bunch grape (Vitis vinifera), questions remain about the seasonal and cultivar-dependent dynamics of muscadine leaf tissue nutrient concentrations. The aim of this study was to assess temporal and cultivar-related differences in tissue nutrient concentration of mature commercially grown muscadines. Leaf tissue nutrient concentration of the muscadine cultivars Carlos and Noble were assessed in three vineyards (Piedmont North Carolina, north Georgia, and south Georgia) at bloom, véraison, and postharvest in 2018 and 2019. Our results show that nitrogen (N), phosphorus (P), and manganese (Mn) were generally above the recommended sufficiency ranges, with calcium increasing over the season—and N, P, and potassium decreasing over the season. ‘Carlos’ had significantly higher levels of N and P, compared with ‘Noble’, while ‘Noble’ showed higher Mn concentration than ‘Carlos’. With this evaluation, we demonstrate the need for a modification in muscadine tissue nutrient sufficiency ranges that are based on cultivar and vine growth stage.}, number={3}, journal={HORTTECHNOLOGY}, author={Rana, Tekan S. and Smith, Erick D. and Hickey, Cain and Hoffmann, Mark}, year={2021}, month={Jun}, pages={280–290} }
 @article{dankbar_phillips_cruz_volk_hoffmann_2021, title={Market challenges for local specialty crop producers during the early phase of COVID-19 in North Carolina}, volume={10}, ISSN={2152-0801}, url={http://dx.doi.org/10.5304/jafscd.2021.104.004}, DOI={10.5304/jafscd.2021.104.004}, abstractNote={In March of 2020, as the number of COVID-19 cases increased in North Carolina (NC), the state encouraged people to stay at home; this included closing restaurants and canceling large events, as well as reducing the number of people gathering. The economic and health crises created by COVID-19 forced specialty crop producers who sell to local markets, such as restaurants and institutions, to pivot their marketing plans as the growing season began to ramp up. This article reports the responses to the first in a series of producer surveys assessing the impact of the economic and health crises on crop production, market channels, and producer concerns during one of the most insecure times in modern history. Results show that producers who could pivot their marketing plans mostly increased sales through online channels and farm stands. However, almost 50% of the usual market channels were reported to be closed due to COVID-19. Additionally, most producers voiced concerns about economic and health safety in the immediate future. To address these concerns as the pandemic unfolded, there was a need for trusted information. Respondents reported that they rely on Extension and other government agencies for this information and updates regarding the pandemic. This survey captured the early impacts of the COVID-19 pandemic on the specialty crop-producing industry in NC. Additional surveys will provide information on how the pandemic evolved during 2020.}, number={4}, journal={Journal of Agriculture, Food Systems, and Community Development}, publisher={Lyson Center for Civic Agriculture and Food Systems}, author={Dankbar, Hannah and Phillips, Ethan and Cruz, Angela and Volk, Emma and Hoffmann, Mark}, year={2021}, month={Aug}, pages={1–11} }
 @article{wagner_tang_salvato_clouse_bartlett_vintila_phillips_sermons_hoffmann_balint-kurti_et al._2021, title={Microbe-dependent heterosis in maize}, volume={118}, ISSN={0027-8424 1091-6490}, url={http://dx.doi.org/10.1073/pnas.2021965118}, DOI={10.1073/pnas.2021965118}, abstractNote={Significance}, number={30}, journal={Proceedings of the National Academy of Sciences}, publisher={Proceedings of the National Academy of Sciences}, author={Wagner, Maggie R. and Tang, Clara and Salvato, Fernanda and Clouse, Kayla M. and Bartlett, Alexandria and Vintila, Simina and Phillips, Laura and Sermons, Shannon and Hoffmann, Mark and Balint-Kurti, Peter J. and et al.}, year={2021}, month={Jul} }
 @article{michuda_goodhue_hoffmann_fennimore_2021, title={Predicting Net Returns of Organic and Conventional Strawberry Following Soil Disinfestation with Steam or Steam Plus Additives}, volume={11}, ISSN={["2073-4395"]}, DOI={10.3390/agronomy11010149}, abstractNote={Pre-plant methods for managing soil-borne pests and diseases are an important priority for many agricultural production systems. This study investigates whether the application of steam is an economically sustainable pre-plant soil disinfestation technique for organic and conventional strawberry (Fragaria ananassa) production in California’s Central Coast region. We analyze net returns from field trials using steam and steam + mustard seed meal (MSM) as pre-plant soil disinfestation treatments. ANOVA tests identify statistically significant differences in net revenues by treatment and trial. Multivariate regressions estimate the magnitude of these effects. Predictive polynomial models identify relationships between net returns and two treatment characteristics: maximum temperature (°C) and time at ≥60 °C (minutes). For organic production, net returns are statistically similar for the steam and steam + MSM treatments. For conventional production, the steam + MSM treatment has significantly higher net returns than the steam treatment. Cross-validated polynomial models outperform the sample mean for prediction of net returns, except for the steam + MSM treatment in conventional production. The optimal degree of the polynomial ranges from 1–4 degrees, depending on the production system and treatment. Results from two of three organic models suggest that maximum soil temperatures of 62–63 °C achieved for 41–44 min maximizes net returns and may be a basis for further experiments.}, number={1}, journal={AGRONOMY-BASEL}, author={Michuda, Aleksandr and Goodhue, Rachael E. and Hoffmann, Mark and Fennimore, Steven A.}, year={2021}, month={Jan} }
 @article{shi_hernandez_hoffmann_2021, title={The influence of stolon harvest frequency and nitrate: ammonium ratio on asexual reproduction of day-neutral strawberries (Fragaria xananassa 'Albion')}, volume={1309}, ISSN={["2406-6168"]}, DOI={10.17660/ActaHortic.2021.1309.41}, journal={IX INTERNATIONAL STRAWBERRY SYMPOSIUM}, author={Shi, X. and Hernandez, R. and Hoffmann, M.}, year={2021}, pages={283–288} }
 @article{shi_hernandez_hoffmann_2021, title={Timing of Stolon Removal Alters Daughter Plant Production and Quality in the Ever-bearing Strawberry 'Albion'}, volume={56}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI15624-20}, abstractNote={Commercial strawberry (Fragaria ×ananassa Duch.) plants propagate through the development of stolons (runners) with attached daughter plants. While it is known that temperature and photoperiod affect strawberry propagation, little knowledge exists on whether cultural methods may influence stolon and daughter plant development. The objective of this study was to characterize the impact of three stolon removal treatments on the development of daughter plants in the ever-bearing strawberry ‘Albion’. Treatments included 1) stolon removal every 7 days, nine times total; 2) stolon removal every 21 days, three times total; and 3) one-time stolon removal after 63 days. Strawberry plants were grown in a controlled environment (26 °C, 507 μmol⋅m–2⋅s–1 photosynthetic photon flux density, 14-hour photoperiod) in soilless media and fertilized with a customized nutrient solution. Mother plants in the 63-day treatment produced more daughter plants (102 per plant), than in the 21-day treatment (33 per plant) and the 7-day treatment (16 per plant). In the 63-day treatment, daughter plants and stolons accumulated to 86.6% of the total biomass, to 42.9% in the 7-day treatment and to 60.6% of total biomass in the 21-day treatment. Mother plant organs (including roots, crown, and leaves) had less dry weight in the 63-day treatment compared with the 7-day treatment and 21-day treatment, respectively. Furthermore, the daughter plants produced at the 63-day treatment had smaller crown diameters (0.65 cm) and less dry weight (0.51 g) and a higher number of fully expanded leaves (2.9) and visible roots (13.4) compared with the 21-day treatment and the 7-day treatment. The results of this study show daughter plant production of strawberry plants declines significantly with shorter stolon removal intervals, indicating the need to adjust stolon removal in strawberry nurseries for optimal daughter plant production.}, number={6}, journal={HORTSCIENCE}, author={Shi, Xiaonan and Hernandez, Ricardo and Hoffmann, Mark}, year={2021}, month={Jun}, pages={650–656} }
 @article{hoffmann_talton_nita_jones_al rwahnih_sudarshana_almeyda_2020, title={First Report of Grapevine red blotch virus, the Causal Agent of Grapevine Red Blotch Disease, in Vitis vinifera in North Carolina}, volume={104}, ISSN={["1943-7692"]}, DOI={10.1094/PDIS-07-19-1539-PDN}, abstractNote={Grapevine red blotch virus (GRBV), genus Grablovirus, family Geminiviridae, is the causal agent for grapevine red blotch disease (GRBD) (Al Rwahnih et al. 2013; Yepes et al. 2018). GRBV has been found in several wine-grape growing regions in the United States (Krenz et al. 2014), as well as in germplasm repositories (Al Rwahnih et al. 2015). However, the incidence of GRBV in parts of the southeastern United States is unknown. Initial observations between August and October of 2017 in North Carolina (NC) vineyards revealed that the commonly grown red cultivars Vitis vinifera ‘Merlot’, ‘Malbec’, and ‘Cabernet franc’ frequently exhibited leaf symptoms similar to those associated with GRBD. The symptoms were seemingly unrelated to location, management, or age of the plants. A total of 80 grapevine samples were collected from eight blocks in six vineyards (10 vines per block) in three different wine-grape growing regions in NC (Upper Hiwassee Highlands American Viticultural Area [AVA], Crest of the Blue Ridge Henderson County AVA, and Yadkin Valley AVA), following the recommended sampling strategy from Foundation Plant Services (FPS, University of California–Davis) (http://fps.ucdavis.edu/samplecollection.cfm). All samples were collected in October 2018. Blocks were selected based on the cultivar and the visibility of symptomatic leaves. Ten vines with leaf symptoms were selected randomly within each block. Three samples per grapevine were collected, sampling both cordons. Samples were directly stored at 4°C and shipped overnight to the NC State University Micropropagation and Repository Unit for further processing. Following FPS protocols, total nucleic acid (TNA) was extracted from leaf petiole tissue using the RNeasy Mini Kit (Qiagen), and samples were analyzed by quantitative reverse transcription PCR (RT-qPCR) for a panel of viruses known to infect grapevine, including GRBV. GRBV was identified in 21 samples of cultivars Merlot and Malbec in Yadkin and Surry Counties, NC (both Yadkin Valley AVA). All positive vines showed GRBD symptoms. To confirm the RT-qPCR results, aliquots of TNA from GRBV-positive samples were run by end-point PCR for further sequencing. GRBV-specific primers as described by Al Rwahnih et al. (2013) were used. RT-PCR yielded products of the expected size (557 bp) for all positive samples, and they were directly sequenced. All the positive samples shared 100% identity with 22 GRBV GenBank accessions, with the top hit being an isolate from Washington state (MF795177), based on BLASTN analysis. Complete genomes of three representative GRBV samples, one from each positive vineyard, were amplified using Phusion Hot Start Flex 2× Master Mix (NEB) and overlapping primers, GRBV-OL-F (5′-ATTCCTGCAGTTCTAGTGAAAG-3′) and GRBV-OL-R (5′-TAGAACTGCAGGAATCGC-3′). Sequencing of the 3.2-kb amplicons was done and the sequences deposited in GenBank (accession nos. MN186403 to MN186405). The GRBV sequences from NC shared 97 to 99% complete genome identities with isolates from Washington State (MF795161 and MF795177). Phylogenetic analysis revealed the clustering of the three NC isolates into GRBV clade 2 (Krenz et al. 2014). This report is part of a comprehensive survey of NC vineyards to study grapevine virus incidence in the state. The source of the virus is unclear; however, studies are underway to determine source and potential vector capacity in NC. To our understanding, this is the first time GRBV is being reported in NC.}, number={4}, journal={PLANT DISEASE}, author={Hoffmann, M. and Talton, W. and Nita, M. and Jones, T. and Al Rwahnih, M. and Sudarshana, M. R. and Almeyda, C.}, year={2020}, month={Apr}, pages={1266–1266} }
 @article{kim_hoffmann_kim_scholler_fennimore_2020, title={Integration of Steam with Allyl-isothiocyanate for Soil Disinfestation}, volume={55}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI14600-20}, abstractNote={Steam has long been used to disinfest greenhouse soils. However, there is increasing interest in expanding the use of steam for in-field soil disinfestation as an alternative to chemical fumigants. Previous studies demonstrated that allyl-isothiocyanate (AITC) reduced viability of weed seeds and plant pathogen propagules, but AITC has a low vapor pressure and is relatively immobile in soil. Heat has been used in the past to enhance the mobility of soil fumigants such as methyl bromide (i.e., “hot gassing”). The effect of steam heat on the mobility of AITC is unknown. The objective of this study was to investigate the potential synergistic effect of steam plus ATIC against weed seeds and a plant pathogen. AITC alone did not reduce the viability of the four weed species and the number of Verticillium dahliae microsclerotia. The steam + AITC treatment reduced the viability of V. dahliae at 12.5 and 18 cm distances by 82% and 88%, respectively, and knotweed and nettle seeds at 70 cm from injection point by 75% and 86%, respectively, from the center of microplots compared with steam alone. The results suggest that AITC and steam have a complementary effect on soilborne pests because steam increases the mobility of AITC.}, number={6}, journal={HORTSCIENCE}, author={Kim, Dong Sub and Hoffmann, Mark and Kim, Steven and Scholler, Bertha A. and Fennimore, Steven A.}, year={2020}, month={Jun}, pages={920–925} }
 @article{hoffmann_ajwa_westerdahl_koike_stanghellini_wilen_fennimore_2020, title={Multitactic Preplant Soil Fumigation with Allyl Isothiocyanate in Cut Flowers and Strawberry}, volume={30}, ISSN={["1943-7714"]}, DOI={10.21273/HORTTECH04362-19}, abstractNote={Allyl isothiocyanate (AITC) is a glucosinolate produced in cruciferous plant species. AITC is known to act as a pesticide on microorganisms, insects, and weeds. Synthetic AITC is registered as a biopesticide for agricultural soil treatment use in the United States and elsewhere in the world. Although a potent pesticide, reports on the weed and pathogen control efficacy of synthetic AITC applied as soil disinfectant are highly variable. Due to the low vapor pressure of AITC, questions remain as to whether pest and weed control efficacy can be improved by combining it with other chemicals. The objective of this study was to assess the control efficacy of AITC stand-alone applications vs. applications, in which AITC was combined with the standard-fumigants chloropicrin, 1,3-dichloropicrin, and methyl isothiocyanate. Two shank-applied on-farm field trials were conducted in cut flower [delphinium (Delphinium elatum), ranunculus (Ranunculus asiaticus)] fields, and two drip tape applied field trials in strawberry (Fragaria ×ananassa) fields in California. Weed pressure, weed seed viability, nematode survival, and pathogen survival of Pythium ultimum, fusarium wilt (Fusarium oxysporum), and verticillium wilt (Verticillium dahliae) were assessed. Cumulative yearly yield of marketable fruit was assessed in the strawberry field trials. The results of this study show that the use of AITC as a stand-alone treatment provided no consistent weed or pathogen control efficacy. However, our results also indicate that shank and drip applied multitactic fumigation approaches with AITC can efficiently control soil-borne diseases and weeds. These findings have potential implications, especially in those areas where certain fumigants are restricted due to regulations and/or availability.}, number={2}, journal={HORTTECHNOLOGY}, author={Hoffmann, Mark and Ajwa, Husein A. and Westerdahl, Becky B. and Koike, Steven T. and Stanghellini, Mike and Wilen, Cheryl and Fennimore, Steven A.}, year={2020}, month={Apr}, pages={251–258} }
 @article{chu_hoffmann_braswell_pelz-stelinski_2019, title={Genetic variation and potential coinfection of Wolbachia among widespread Asian citrus psyllid (Diaphorina citri Kuwayama) populations}, volume={26}, ISSN={["1744-7917"]}, DOI={10.1111/1744-7917.12566}, abstractNote={Abstract}, number={4}, journal={INSECT SCIENCE}, author={Chu, Chia-Ching and Hoffmann, Mark and Braswell, W. Evan and Pelz-Stelinski, Kirsten S.}, year={2019}, month={Aug}, pages={671–682} }
 @article{hoffmann_fennimore_2017, title={A Soil Probe System to Evaluate Weed Seed Survival in Soil Disinfestation Trials}, volume={31}, ISSN={0890-037X 1550-2740}, url={http://dx.doi.org/10.1017/WET.2017.36}, DOI={10.1017/WET.2017.36}, abstractNote={Weed seed viability is an important parameter to assess the efficacy of soil disinfestation methods like fumigation and steam. In field experiments, seed samples are commonly placed in permeable bags and buried at several depths in soil before the application of soil disinfestation treatments. The seed samples are recovered several days to weeks after treatment and then seed viability is determined in the laboratory. The process of sample installation and recovery is time consuming and may expose personnel to hazardous conditions such as heat or fumigants. Described is a custom soil probe system, developed to simplify installation and recovery of weed seeds from soil. Each soil probe is capable of holding weed seed samples at three different depths up to 30 cm. The following hypothesis was tested: viability of weed seeds is similarly affected by soil disinfestation treatments whether the seeds were contained in the soil probe system or seed bag assays. Two different soil disinfestation trials were conducted: (1) a repeated micro-plot study (USDA Salinas, 1 m-2), using steam as a soil disinfestation treatment and (2) a field study in a commercial strawberry field with 1,3-dicloropropene plus chloropicrin (Pic-Clor 60) as soil disinfestation method. In both studies, seed viability of burning nettle, common knotweed, and common purslane (tetrazolium assay) and germination rates of yellow nutsedge tubers were assessed. Results indicate that the soil probe system can be used as an alternative to the seed bag assay to assess weed control efficacy of described soil disinfestation methods.}, number={5}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Hoffmann, Mark and Fennimore, Steven A.}, year={2017}, month={Sep}, pages={752–760} }
 @article{hoffmann_barbella_miller_broome_martin_koike_rachuy_greene_dorn_goodhue_et al._2017, title={Weed and pathogen control with steam in California strawberry production}, ISSN={0567-7572 2406-6168}, url={http://dx.doi.org/10.17660/ActaHortic.2017.1156.88}, DOI={10.17660/ActaHortic.2017.1156.88}, number={1156}, journal={Acta Horticulturae}, publisher={International Society for Horticultural Science (ISHS)}, author={Hoffmann, M. and Barbella, A. and Miller, T. and Broome, J. and Martin, F. and Koike, S. and Rachuy, J. and Greene, I. and Dorn, N. and Goodhue, R. and et al.}, year={2017}, month={Apr}, pages={593–602} }
 @article{hoffmann_ruehl_eisenbeis_huber_2016, title={Grape root as habitat: overwintering and population dynamics of grape phylloxera (Daktulosphaira vitifoliae
 Fitch) in temperate climate viticulture}, volume={22}, ISSN={1322-7130}, url={http://dx.doi.org/10.1111/ajgw.12219}, DOI={10.1111/ajgw.12219}, abstractNote={Background and Aims 
 
Daktulosphaira vitifoliae Fitch (grape phylloxera, Phylloxeridae) is one of the most devastating pests in viticulture, mainly because of their root feeding activity. Up to today fundamental relations between belowground habitat and population dynamics remain unclear. In this 2-year study, we investigated the relations between grape phylloxera population and phenotypic traits of roots and feedings sites. 
 
 
 
Methods and Results 
 
We extracted root and soil samples frequently of two closely related mature rootstocks [Vitis berlandieri × V. riparia (cvs 5C and 125AA)]. We quantified and characterised larval population and crowding and assessed root gall pigmentation, root morphology and soil parameters. We identified and described three stages of seasonal population dynamics: reproduction, overwintering and declining. Further, we demonstrated a significant impact of root gall pigmentation and crowding on population dynamics. 
 
 
 
Conclusions 
 
In temperate climates, grape phylloxera is able to overwinter at high density on roots of American rootstocks. Population dynamics are highly dependent on root gall development and the ability to crowd. 
 
 
 
Significance of the Study 
 
The results of our study are considered to have a significant impact on the development of management strategies for grape phylloxera.}, number={2}, journal={Australian Journal of Grape and Wine Research}, publisher={Wiley}, author={Hoffmann, M. and Ruehl, E.H. and Eisenbeis, G. and Huber, L.}, year={2016}, month={Mar}, pages={271–278} }
 @article{chu_gill_hoffmann_pelz-stelinski_2016, title={Inter-Population Variability of Endosymbiont Densities in the Asian Citrus Psyllid (Diaphorina citri Kuwayama)}, volume={71}, ISSN={0095-3628 1432-184X}, url={http://dx.doi.org/10.1007/s00248-016-0733-9}, DOI={10.1007/s00248-016-0733-9}, abstractNote={The Asian citrus psyllid (Diaphorina citri Kuwayama) is an insect pest capable of transmitting Candidatus Liberibacter asiaticus (CLas), the causal agent of citrus greening in North America. D. citri also harbors three endosymbionts, Wolbachia, Candidatus Carsonella ruddii, and Candidatus Profftella armatura, which may influence D. citri physiology and fitness. Although genomic researches on these bacteria have been conducted, much remains unclear regarding their ecology and inter-population variability in D. citri. The present work examined the densities of each endosymbiont in adult D. citri sampled from different populations using quantitative PCR. Under field conditions, the densities of all three endosymbionts positively correlated with each other, and they are associated with D. citri gender and locality. In addition, the infection density of CLas also varied across populations. Although an analysis pooling D. citri from different populations showed that CLas-infected individuals tended to have lower endosymbiont densities compared to uninfected individuals, the difference was not significant when the population was included as a factor in the analysis, suggesting that other population-specific factors may have stronger effects on endosymbiont densities. To determine whether there is a genetic basis to the density differences, endosymbiont densities between aged CLas-negative females of two D. citri populations reared under standardized laboratory conditions were compared. Results suggested that inter-population variability in Wolbachia infection density is associated with the genotypes of the endosymbiont or the host. Findings from this work could facilitate understanding of D. citri-bacterial associations that may benefit the development of approaches for managing citrus greening, such as prevention of CLas transmission.}, number={4}, journal={Microbial Ecology}, publisher={Springer Nature}, author={Chu, Chia-Ching and Gill, Torrence A. and Hoffmann, Mark and Pelz-Stelinski, Kirsten S.}, year={2016}, month={Feb}, pages={999–1007} }
 @article{hoffmann_ruehl_eisenbeis_huber_2015, title={Indications for rootstock related ecological preferences of grape phylloxera (Daktulosphaira vitifoliae Fitch)}, volume={54}, journal={Vitis}, author={Hoffmann, M. and Ruehl, E.H. and Eisenbeis, G. and Huber, L.}, year={2015}, pages={137–142} }
 @article{coy_hoffmann_kingdom gibbard_kuhns_pelz-stelinski_stelinski_2014, title={Nested-quantitative PCR approach with improved sensitivity for the detection of low titer levels of Candidatus Liberibacter asiaticus in the Asian citrus psyllid, Diaphorina citri Kuwayama}, volume={102}, ISSN={0167-7012}, url={http://dx.doi.org/10.1016/j.mimet.2014.04.007}, DOI={10.1016/j.mimet.2014.04.007}, abstractNote={Candidatus Liberibacter asiaticus (CLas) is a phloem-limited bacterium transmitted by the Asian citrus psyllid, Diaphorina citri, and the presumptive causal agent of citrus greening disease. The current method of detection for CLas within plant and insect samples is by a presence/absence qPCR assay using the CLas 16S rDNA gene target. Although qPCR is highly sensitive, low bacterial titers or suboptimal qPCR conditions can result in false-negatives. Using a nested qPCR assay, we determined the false-negative rate of the 16S presence/absence qPCR assay was greater than 50%. Studies to determine the performance parameters of the qPCR assays for CLas 16S and Wingless (Wg), the D. citri endogenous gene, using plasmid and psyllid DNA, revealed suboptimal and variable performance of the 16S assay in psyllid samples. Average efficiencies and sensitivity limits of the plasmid assays were 99.0% and 2.7 copies of template for Wg, respectively, and 98.5% and 2.2-22.1 copies for 16S, respectively. Variability in efficiency was significantly greater in psyllid samples for both gene targets compared to the corresponding plasmid assays, and efficiencies as low as 76% were obtained for 16S. A secondary structure analysis revealed the formation of two stem-loop structures that block the forward and probe binding sites in the 16S template, which could hinder amplification. In summary, our results suggest that suboptimal qPCR efficiency is not uncommon for the 16S presence/absence qPCR assay, which combined with lowCLas titers in some samples, could contribute significantly to the under-reporting of CLas infection in psyllid and plant samples.}, journal={Journal of Microbiological Methods}, publisher={Elsevier BV}, author={Coy, M.R. and Hoffmann, M. and Kingdom Gibbard, H.N. and Kuhns, E.H. and Pelz-Stelinski, K.S. and Stelinski, L.L.}, year={2014}, month={Jul}, pages={15–22} }
 @article{hoffmann_coy_gibbard_pelz-stelinski_2014, title={Wolbachia Infection Density in Populations of the Asian Citrus Psyllid (Hemiptera: Liviidae)}, volume={43}, ISSN={0046-225X 1938-2936}, url={http://dx.doi.org/10.1603/en14193}, DOI={10.1603/en14193}, abstractNote={ABSTRACT 
 The symbiotic relationships between bacteria of the genus Wolbachia (order Rickettsiales) and their arthropod hosts are diverse and can range from mutualism to parasitism. Whereas effects of Wolbachia on host biology are well investigated, little is known about diversity and abundance of Wolbachia in their natural hosts. The phloem-feeding Asian citrus psyllid, Diaphorina citri (Kuwayama) (Hemiptera: Liviidae), is naturally infected with Wolbachia (wDi). In the current study, we calculated the within-host density of Wolbachia in Florida D. citri populations using quantitative polymerase chain reaction for detection of the Wolbachia outer surface protein gene, wsp. Gene quantities were normalized to the D. citri wingless gene (Wg) to estimate Wolbachia abundance in individual D. citri. Using this method, significant geographic differences in Wolbachia densities were detected among Florida D. citri populations, with higher infection levels occurring in male versus female hosts.}, number={5}, journal={Environmental Entomology}, publisher={Oxford University Press (OUP)}, author={Hoffmann, M. and Coy, M. R. and Gibbard, H. N. Kingdom and Pelz-Stelinski, K. S.}, year={2014}, month={Oct}, pages={1215–1222} }
 @article{hoffmann_ruehl_presser_2012, title={Ein Leitfaden zur Identifikation von Wurzelschimmel (Roesleria subterranea (Weinm.) Redhead) in Ertragsanlagen = Guidelines to identify grape root rot (Roesleria subterranea (Weinm.) Redhead) in vineyards}, journal={Deutsches Weinmagazin = German Wine Magazine}, author={Hoffmann, M. and Ruehl, E.H. and Presser, C.}, year={2012}, month={Sep}, pages={16–19} }
 @inbook{hoffmann_huber_ruehl_2012, title={Grape root rot (Roesleria subterranea (Weinm.) Redhead – Biology, Distribution and possible causes}, booktitle={Annuals of German Viticulture}, author={Hoffmann, M. and Huber, L. and Ruehl, E.H.}, year={2012} }
 @article{hoffmann_ruehl_huber_eisenbeis_kirchmair_2011, title={A scanner based approach to assess grape root infesting parasites in field.}, volume={904}, ISSN={0567-7572 2406-6168}, url={http://dx.doi.org/10.17660/actahortic.2011.904.14}, DOI={10.17660/actahortic.2011.904.14}, journal={Acta Horticulturae}, publisher={International Society for Horticultural Science (ISHS)}, author={Hoffmann, M. and Ruehl, E.H. and Huber, L. and Eisenbeis, G. and Kirchmair, M.}, year={2011}, month={Aug}, pages={101–109} }
 @inbook{hoffmann_huber_ruehl_eisenbeis_2011, title={Morphologische Wurzelsystemparameter bei Unterlagsreben der Sorte 5C (Vitis riparia x Vitis berlandieri) unter Berücksichtigung der Reblauspopulation (Daktulosphaira vitifoliae Fitch) und der Bodentemperatur}, volume={18}, booktitle={Mitteilungen Agrarwissenschaften}, author={Hoffmann, M. and Huber, L. and Ruehl, E.H. and Eisenbeis, G.}, editor={Merbach, W. and Ruppel, S. and Augustin, J.Editors}, year={2011}, pages={43–51} }
 @article{hoffmann_ruehl_2010, title={Questions regarding the distribution of grape root rot Roesleria subterranea (Weinm.) Redhead}, volume={43}, journal={German Wine Magazine}, author={Hoffmann, M. and Ruehl, E.H.}, year={2010}, pages={16–17} }
 @article{kirchmair_neuhauser_strasser_voloshchuk_hoffmann_huber_2009, title={Biological Control of Grape Phylloxera – a historical review and future prospects}, volume={816}, ISSN={0567-7572 2406-6168}, url={http://dx.doi.org/10.17660/actahortic.2009.816.1}, DOI={10.17660/actahortic.2009.816.1}, journal={Acta Horticulturae}, publisher={International Society for Horticultural Science (ISHS)}, author={Kirchmair, M. and Neuhauser, S. and Strasser, H. and Voloshchuk, N. and Hoffmann, M. and Huber, L.}, year={2009}, month={Mar}, pages={13–18} }
 @article{huber_hoffmann_rühl_kirchmair_2009, title={Disease supressiveness of vineyard soils infested with Grape Phylloxera}, volume={816}, ISSN={0567-7572 2406-6168}, url={http://dx.doi.org/10.17660/actahortic.2009.816.7}, DOI={10.17660/actahortic.2009.816.7}, journal={Acta Horticulturae}, publisher={International Society for Horticultural Science (ISHS)}, author={Huber, L. and Hoffmann, M. and Rühl, E.H. and Kirchmair, M.}, year={2009}, month={Mar}, pages={41–52} }
 @article{huber_eisenbeis_hoffmann_neuhauser_porten_ruehl_2006, title={Absterbeerscheinungen und Kümmerwuchs verursacht durch den Wurzelschimmelerreger Roesleria subterranea (Weinm.) Redhead}, journal={Deutsches Weinmagazin}, author={Huber, L. and Eisenbeis, G. and Hoffmann, M. and Neuhauser, S. and Porten, M. and Ruehl, E.H.}, year={2006}, month={Mar}, pages={25–31} }
 @article{huber_eisenbeis_hoffmann_neuhauser_porten_ruehl_2006, title={Bekämpfung des Wurzelschimmels}, journal={Die Winzer-Zeitschrift}, author={Huber, L. and Eisenbeis, G. and Hoffmann, M. and Neuhauser, S. and Porten, M. and Ruehl, E.H.}, year={2006}, month={May}, pages={35–37} }
 @article{kirchmair_hoffmann_neuhauser_huber_2006, title={Persistence of GranMet®, a Metarhizium anisopliae based product, in grape phylloxera infested vineyards}, volume={30}, number={7}, journal={IOBC wprs Bulletin}, author={Kirchmair, M. and Hoffmann, M. and Neuhauser, S. and Huber, L.}, editor={Enkerli, J.Editor}, year={2006}, pages={137–142} }
 @article{huber_eisenbeis_hoffmann_neuhauser_porten_ruehl_2006, title={Wurzelschimmel - verborgene Gefahr im Untergrund}, journal={Die Winzer-Zeitschrift}, author={Huber, L. and Eisenbeis, G. and Hoffmann, M. and Neuhauser, S. and Porten, M. and Ruehl, E.H.}, year={2006}, month={Apr}, pages={34–35} }