@article{freund_kerns_butler_ahmed_gannon_2024, title={Effect of mowing timing and clipping collection practices on azoxystrobin distribution, persistence, and efficacy}, volume={9}, ISSN={["1435-0653"]}, DOI={10.1002/csc2.21365}, abstractNote={Abstract Previous research suggests mowing practices following azoxystrobin application alter pest control and residue fate. Azoxystrobin, an acropetal penetrant quinone outside inhibitor fungicide, is commonly applied in turfgrass and other agricultural settings, protecting desired plants from fungal pathogens by inhibiting fungal growth. Field research was initiated in Raleigh, NC, and repeated in time to assess the effect of post‐application mowing timing and clipping collection practices on azoxystrobin residue persistence in tall fescue ( Schedonorus arundinaceus Schreb.). At trial initiation, azoxystrobin was applied at the maximum single application rate (0.61 kg ai ha −1 ) to tall fescue plots. To determine the effect of initial mowing timing, plots were mowed (9.5 cm) at 0, 1, 2, 3, 7, or 14 days after application (DAA). To determine the effect of clipping removal, plots were mowed at 3, 10, and 17 DAA and clippings were either returned to the canopy or bagged and removed. Concurrently, soil cores (92 cm 2 ) were collected at 3, 7, 14, and 21 DAA and then segmented into remaining aboveground vegetation and soil (0.0‐ to 2.5‐cm depth) for residue analyses. Mowing timing affected azoxystrobin residue in the vegetation and in soil. When clippings were returned to the canopy, 5% more azoxystrobin was detected in the vegetation at 7 and 14 DAA. At 3 and 7 DAA, in the soil, returning clippings resulted in >3% more of the applied azoxystrobin compared to removing clippings. Data from this research may allow for extended fungicide intervals for brown patch suppression and demonstrate the importance of returning clipping to turf systems to retain azoxystrobin residues.}, journal={CROP SCIENCE}, author={Freund, Daniel R. and Kerns, James P. and Butler, E. Lee and Ahmed, Khalied A. and Gannon, Travis W.}, year={2024}, month={Sep} }
 @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{haug_ahmed_gannon_richardson_2021, title={Absorption and translocation of florpyrauxifen-benzyl in ten aquatic plant species}, volume={69}, ISSN={["1550-2759"]}, DOI={10.1017/wsc.2021.38}, abstractNote={AbstractAdditional active ingredients are needed for use in aquatic systems to respond to new threats or treatment scenarios, enhance selectivity, reduce use rates, and mitigate the risk of herbicide resistance. Florpyrauxifen-benzyl is a new synthetic auxin developed for use as an aquatic herbicide. A study was conducted at North Carolina State University in which 10 µg L−1 of 25% radiolabeled florpyrauxifen-benzyl was applied to the isolated shoot tissue of 10 different aquatic plant species to elucidate absorption and translocation patterns in these species. Extremely high levels of shoot absorption were observed for all species, and uptake was rapid. Highest shoot absorptions were observed for crested floatingheart [Nymphoides cristata (Roxb.) Kuntze] (A192 = 20 µg g−1), dioecious hydrilla [Hydrilla verticillata (L. f.) Royle] (A192 = 25.3 µg g−1), variable watermilfoil (Myriophyllum heterophyllum Michx.) (A192 = 40.1 µg g−1), and Eurasian watermilfoil (Myriophyllum spicatum L.) (A192 = 25.3 µg g−1). Evidence of translocation was observed in all rooted species tested, with the greatest translocation observed in N. cristata (1.28 µg g−1 at 192 h after treatment). The results of this study add to the growing body of knowledge surrounding the behavior of this newly registered herbicide within aquatic plants.}, number={6}, journal={WEED SCIENCE}, author={Haug, Erika J. and Ahmed, Khalied A. and Gannon, Travis W. and Richardson, Rob J.}, year={2021}, month={Nov}, pages={624–630} }
 @article{stephens_kerns_ahmed_gannon_2021, title={Influence of post-application irrigation and mowing timing on fungicide fate on a United States Golf Association golf course putting green}, volume={6}, ISSN={["1537-2537"]}, DOI={10.1002/jeq2.20249}, abstractNote={AbstractFungicides are routinely applied to golf course putting greens throughout the growing season. Gaining a better understanding of fungicide fate can improve fungicide use and stewardship. Therefore, optimizing fungicide applications with post‐application management practices may enhance fungicide movement and limit potential off‐target effects. Two field studies were initiated on a golf course putting green to evaluate the influence of post‐fungicide application irrigation and mowing timing on fungicide movement into the soil profile and removal in turfgrass clippings. Plots were treated with a single application of either pyraclostrobin, triadimefon, or penthiopyrad and received 0.64 cm post‐application irrigation immediately or 6 h after application or received no post‐application irrigation. Clippings were collected 0, 1, and 3 d after treatment (DAT). Cores were harvested 0, 1, 3, 5, 7, and 14 DAT and dissected into the remaining aboveground vegetation (RAV; verdure/thatch; 0‐to‐2.5‐, 2.5‐to‐5.1‐, and 5.1‐to‐7.6‐cm soil subsections). A small amount of fungicide (<3.6%) was removed with clippings regardless of mowing and irrigation treatment. Post‐application irrigation treatment influenced fungicide movement; however, >50% of fungicide remained restricted to the RAV for the first 3 DAT. Less fungicide remained restricted to the RAV, and more fungicide was detected in deeper soil depths when plots were irrigated immediately after application. Fungicide was only detected at the 5.1‐to‐7.6‐cm depth when plots were irrigated immediately. Applying post‐application irrigation immediately may result in more fungicide moving down to soilborne targets. Irrigating 6 h after application facilitated moderate fungicide movement compared with irrigating immediately but was better than no post‐application irrigation.}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Stephens, Cameron M. and Kerns, James P. and Ahmed, Khalied A. and Gannon, Travis W.}, year={2021}, month={Jun} }
 @article{jeffries_gannon_brosnan_ahmed_breeden_2016, title={Factors Influencing Dislodgeable 2, 4-D Plant Residues from Hybrid Bermudagrass (Cynodon dactylon L. x C. transvaalensis) Athletic Fields}, volume={11}, ISSN={["1932-6203"]}, DOI={10.1371/journal.pone.0148992}, abstractNote={Research to date has confirmed 2,4-D residues may dislodge from turfgrass; however, experiments have not been conducted on hybrid bermudagrass (Cynodon dactylon L. x C. transvaalensis), the most common athletic field turfgrass in subtropical climates. More specifically, previous research has not investigated the effect of post-application irrigation on dislodgeable 2,4-D residues from hybrid bermudagrass and across turfgrass species, research has been nondescript regarding sample time within a d (TWD) or conducted in the afternoon when the turfgrass canopy is dry, possibly underestimating potential for dislodgement. The effect of irrigation and TWD on 2,4-D dislodgeability was investigated. Dislodgeable 2,4-D amine was reduced > 300% following irrigation. From 2 to 7 d after treatment (DAT), ≤ 0.5% of applied 2,4-D was dislodged from irrigated turfgrass, while ≤ 2.3% of applied 2,4-D was dislodged when not irrigated. 2,4-D dislodgeability decreased as TWD increased. Dislodgeable 2,4-D residues declined to < 0.1% of the applied at 1 DAT– 13:00, and increased to 1 to 3% of the applied 2 DAT– 5:00, suggesting 2,4-D re-suspended on treated turfgrass vegetation overnight. In conclusion, irrigating treated turfgrass reduced dislodgeable 2,4-D. 2,4-D dislodgeability increased as TWD decreased, which was attributed to non-precipitation climatic conditions favoring turfgrass canopy wetness. This research will improve turfgrass management practices and research designed to minimize human 2,4-D exposure.}, number={2}, journal={PLOS ONE}, author={Jeffries, Matthew D. and Gannon, Travis W. and Brosnan, James T. and Ahmed, Khalied A. and Breeden, Gregory K.}, year={2016}, month={Feb} }
 @article{gannon_jeffries_ahmed_2017, title={Irrigation and Soil Surfactants Affect Abamectin Distribution in Soil}, volume={57}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2016.05.0320}, abstractNote={Nematodes are microscopic, soil‐dwelling organisms that adversely affect many turfgrass systems, including golf course putting greens. Abamectin controls many nematode species in golf course putting greens; however, high sorption to accumulated organic matter near the soil surface in established turfgrass systems may limit its distribution in soil, thereby limiting its efficacy. Field research was conducted on ‘A1/A4’ creeping bentgrass and ‘Champion’ ultradwarf bermudagrass putting greens to evaluate abamectin distribution in soil following treatment regimens including abamectin application (37 g a.i. ha–1) alone, or tank‐mixed with soil surfactant (Revolution) in tandem with various irrigation timings to promote downward distribution. Laboratory research was also conducted to evaluate 14C‐abamectin soil distribution via treatments comprised of various combinations of simulated irrigation amounts and timings, as well as soil surfactant type (Dispatch or Qualibra) and timing with respect to abamectin application. Abamectin distributed similarly in soil across turfgrass species in field research. At 7 d after treatment (DAT), all irrigation–soil surfactant regimens increased abamectin distribution to the 0‐ to 2.5‐cm soil depth compared with broadcast spray alone; however, no evaluated regimen resulted in >2% of the applied abamectin movement beyond 2.5 cm. In laboratory experiments, 14C‐abamectin soil distribution was affected most by soil surfactant at 3 DAT, with Qualibra increasing distribution (8.2 to 18.4% of applied) to 7.5 cm depth compared with Dispatch or no surfactant. As in field research, irrigation amounts and timings generally affected 14C‐abamectin similarly. This research highlights practices to enhance distribution into the profile, thereby increasing bioavailability and efficacy.}, number={2}, journal={CROP SCIENCE}, author={Gannon, Travis W. and Jeffries, Matthew D. and Ahmed, Khalied A.}, year={2017}, pages={573–580} }
 @article{jeffries_yelverton_ahmed_gannon_2016, title={Persistence in and Release of 2,4-D and Azoxystrobin from Turfgrass Clippings}, volume={45}, ISSN={["1537-2537"]}, DOI={10.2134/jeq2016.03.0081}, abstractNote={Research has shown that pesticide residue in clippings from previously treated turfgrass may become bioavailable as grass decomposes, adversely affecting off‐target organisms. We conducted a field study to quantify 2,4‐D (2,4‐dichlorophenoxyacetic acid) and azoxystrobin (methyl(E)‐2‐{2[6‐(2‐cyanophenoxy)pyrmidin‐4‐yloxy]phenyl}‐3‐methoxyacrylate) residues in turfgrass clippings collected from hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt–Davy], tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire], and zoysiagrass (Zoysia japonica Steud.). A subsequent greenhouse experiment was conducted to measure pesticide release from clippings into water. 2,4‐D (1.6 kg a.i. ha−1) and azoxystrobin (0.6 kg a.i. ha−1) were applied to field plots at 32, 16, 8, 4, 2, 1, or 0 d before collection of the clippings. Clippings were collected from each experimental unit to quantify pesticide release from clippings into water. Both 2,4‐D and azoxystrobin were detected when turfgrass was treated over the 32‐d experimental period, suggesting that clipping management should be implemented for an extended period of time after application. Pesticide residue was detected in all water samples collected, confirming 2,4‐D and azoxystrobin release from turfgrass clippings; however, pesticide release varied between compounds. Two days after clippings were incorporated in water, 39 and 10% of 2,4‐D and azoxystrobin were released from clippings, respectively. Our research supports the currently recommended practice of returning clippings to the turfgrass stand when mowing because removal of 2,4‐D and azoxystrobin in clippings may reduce pest control and cause adverse off‐target impacts.Core Ideas
2,4‐D and azoxystrobin residues were detected in clippings 32 d after treatment.
2,4‐D and azoxystrobin were released from turfgrass clippings into water.
Pesticide release from turfgrass clippings into water varied between compounds.
}, number={6}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Jeffries, Matthew D. and Yelverton, Fred H. and Ahmed, Khalied A. and Gannon, Travis W.}, year={2016}, pages={2030–2037} }