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Browsing by Author "Singh, Vijay"

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    2021 Field Crops PMG
    Balota, Maria; Besancon, Thierry E.; Cahoon, Charles W.; Chandra, Rakesh; Currin, John F.; Day, Eric R.; Flessner, Michael; Frame, William Hunter, 1985-; Frank, Daniel; Hines, Tommy; Herbert, D. Ames Jr.; Johnson, Charles S.; Johnson, Quintin; Jordan, David; Koehler, Alyssa; Langston, David B.; Lamb, Curt; Lingenfelter, Dwight; McCoy, Tim; Singh, Vijay; Taylor, Sally V.; VanGessel, Mark; Vollmer, Kurt; Wallace, John M.; Wilson, James (Virginia Cooperative Extension, 2021-02-12)
    The Virginia Pest Management Guide (PMG) series lists options for management of major pests: diseases, insects, nematodes, and weeds. These guides are produced by Virginia Cooperative Extension and each guide is revised annually. PMG recommendations are based on research conducted by the Research and Extension Division of Virginia Tech, in cooperation with other land-grant universities, the USDA, and the pest management industry. Commercial products are named in this publication for informational purposes only. Virginia Cooperative Extension does not endorse these products and does not intend discrimination against other products that also may be suitable.
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    2021 Field Crops PMG - Weed Control
    Flessner, Michael; Singh, Vijay; Besan'on, Theirry E.; Chandran, Rakesh; Hines, Tommy; Johnson, Quintin; Lingenfelter, Dwight; VanGessel, Mark; Vollmer, Kurt Matthew; Wallace, John (Virginia Cooperative Extension, 2021-02-12)
    This is a chapter of the 2021 Field Crops PMG. The Virginia Pest Management Guide (PMG) series lists options for management of major pests: diseases, insects, nematodes, and weeds. These guides are produced by Virginia Cooperative Extension and each guide is revised annually. PMG recommendations are based on research conducted by the Research and Extension Division of Virginia Tech, in cooperation with other land-grant universities, the USDA, and the pest management industry. Commercial products are named in this publication for informational purposes only. Virginia Cooperative Extension does not endorse these products and does not intend discrimination against other products that also may be suitable.
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    2021 Home Grounds and Animals PMG - Index
    Balota, Maria; Besancon, Thierry E.; Cahoon, Charles W.; Chandran, Rakesh; Currin, John F.; Day, Eric R.; Flessner, Michael; Frame, William Hunter; Frank, Daniel; Hines, Tommy; Herbert, Ames Jr.; Johnson, Charles S.; Johnson, Quintin; Jordan, David; Koehler, Alyssa; Langston, David B.; Laub, Curt; Lingenfelter, Dwight; McCoy, Tim; Singh, Vijay; Taylor, Sally V.; VanGessel, Mark; Vollmer, Kurt; Wallace, John M.; Wilson, James (Virginia Cooperative Extension, 2021-02-12)
    This is a chapter of the 2021 Field Crops PMG. The Virginia Pest Management Guide (PMG) series lists options for management of major pests: diseases, insects, nematodes, and weeds. These guides are produced by Virginia Cooperative Extension and each guide is revised annually. PMG recommendations are based on research conducted by the Research and Extension Division of Virginia Tech, in cooperation with other land-grant universities, the USDA, and the pest management industry. Commercial products are named in this publication for informational purposes only. Virginia Cooperative Extension does not endorse these products and does not intend discrimination against other products that also may be suitable.
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    2021 Virtual Eastern Shore Agricultural Conference and Trade Show
    Pittman, Theresa; Deitch, Ursula T.; Reiter, Mark S.; Singh, Vijay; Mason, John; Duerksen, Keren; Haymaker, Joseph; Doughty, Helene; Holshouser, David Lee, 1963-; Langston, David B.; Flessner, Michael; Rideout, Steven L.; Thomason, Wade E.; McCullough, Chris T.; Sutton, Kemper L.; Bekelja, Kyle; Kuhar, Thomas P.; Richardson, Bruce; Harper, Robert; Richardson, Brett; Shockley, Bill (Virginia Cooperative Extension, 2021-03-12)
    Join us for the 2021 virtual Eastern Shore Agricultural Conference and Trade Show! Hear updates and continuing education presentations that are pertinent to Eastern Shore of Virginia growers.
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    2022-2023 Mid-Atlantic Commercial Vegetable Production Recommendations
    Reiter, Mark S.; Samtani, Jayesh; Torres Quezada, Emmanuel; Singh, Vijay; Doughty, H.; Kuhar, Thomas P.; Sutton, Kemper; Wilson, James; Langston, David B.; Rideout, Steven; Parkhurst, James; Strawn, Laura K. (Virginia Cooperative Extension, 2022-11-30)
    This copy of the 2022/2023 Mid-Atlantic Commercial Vegetable Production Recommendations replaces all previous editions of the Commercial Vegetable Production Recommendations published individually for Delaware, Maryland, New Jersey, Pennsylvania, Virginia, and West Virginia. Information presented in this publication is based on research results from the University of Delaware, the University of Maryland, Rutgers - The State University of New Jersey, The Pennsylvania State University, Virginia Polytechnic Institute and State University, West Virginia University, and the U.S. Department of Agriculture, combined with industry and grower knowledge and experience. This publication will be revised biennially. In January 2023, a Critical Update with important updates for this publication will be communicated through local Extension Agents and Vegetable Specialists. The editors welcome constructive criticism and suggestions from growers and industry personnel who may wish to help improve future editions of this publication. These recommendations are intended for the commercial vegetable grower who has to make numerous managerial decisions. Although the proper choices of variety, pesticides, equipment, irrigation, fertilizer, and cultural practices are the individual vegetable grower’s responsibility, it is intended that these recommendations will facilitate decision-making. Recommended planting dates will vary across the six-state region. Local weather conditions, grower experience, and variety may facilitate successful harvest on crops planted outside the planting dates listed in this guide. This can be evaluated in consultation with the local agents and state specialists. Government agencies and other organizations administrating crop insurance programs or other support programs should contact local Extension agents and/or vegetable specialists for guidance. Not to be used by home gardeners.
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    Assessing Spray Deposition and Weed Control Efficacy from Aerial and Ground Equipment in Managed Turfgrass Systems
    Koo, Daewon (Virginia Tech, 2024-05-24)
    There is a growing interest in agricultural spray drone (ASD) use for herbicide application in managed turfgrass systems, which historically has precluded aerial application. Considering pesticide deposition accuracy is of utmost importance in managed turfgrass systems, a thorough examination of factors that influence ASD spray deposition patterns is needed. A python-based spray deposition pattern analysis tool, SprayDAT, was developed to estimate spray quality utilizing a cost-effective continuous sampling technique involving digital soand spectrophotometric analysis of blue colorant stains on white Kraft paper. This technique cost 0.2 cents per USD spent on traditional water-sensitive paper (WSP) allowing for continuous sampling necessary for the highly variable deposition patterns delivered by an ASD. SprayDAT conserved droplet densities and more accurately detected stain objects compared to a commonly utilized software, DepositScan, which overestimated stain sizes. However, droplet density exhibited an upper asymptote at 22% stain cover when relating volume median diameter (VMD) due to increasing overlap of stain objects. Spread factor of blue colorant stains was fit to a 2-parameter power equation when compared across six discrete droplet sizes between 112 and 315 µm when droplets were captured in a biphasic solution of polydimethylsiloxane of 100 cSt over 12,500 cSt viscosities. Cumulative digitally assessed stain objects underestimated application volume 270% when compared to the predicted output based on flow rate, coverage, and speed. SprayDAT incorporates a standard curve based on colorant extraction and spectrophotometric analysis to correct this error such that total stain area accurately estimates application volume to within 9%. This relationship between extracted colorant and total stain area, however, is dependent on droplet size spectra. SprayDAT allows users to customize standard curves to address this issue. Using these analysis techniques, continuous sampling of a 29.3-m transect perpendicular to an ASD or ground sprayer spray swath resolved that increasing ASD operational height increases drift and effective swath width while effective application rate, total deposition, and smooth crabgrass control by quinclorac herbicide decreases. Deposition under the ASD was heterogeneous as the coefficient of variation (CV) within the targeted swath exceeded 30% regardless of operational height. At higher operational heights, relative uniformity of spray pattern was improved but droplet density at 11.7 m away from the intended swath edge was up to four times greater and total spray deposited was up to 60% reduced at the highest heights. For each 1-m increase in ASD operational height, 6% of the deposited spray solution, 11% of the effective application rate within the targeted swath, and 7% of smooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.] population reduction declined. Subsequent studies suggested that total deposition loss with increasing operational height of ASD were likely due to droplet evaporation. Discrete-sized droplets subjected to a 5-m fall in a windless environment exhibited a sigmoidal relationship where 98% volume of 135-µm droplets and approximately 67% volume of 177 – 283 µm diameter droplets evaporated. Addition of drift reduction agents (DRAs) or choosing different nozzle types altered the initial droplet density generated by a flat-fan nozzle. Regardless of DRA additions or nozzle replacement, the distance required to lose 50% of small droplets (< 150 µm diameter) was 6.6 m. Air induction nozzles and DRA admixtures also conserved smooth crabgrass control across 2- and 6-m operational heights, where control was reduced at the 6-m height with a flat fan nozzle without DRA. Spray deposition pattern analysis for multipass ASD and ground applications was conducted by utilizing nighttime UV-fluorescence aerial photography and weed infestation counts in a digitally overlaid grid. Results show that under-application across all devices was consistent and averaged 12%, whereas at least 14% more over-application on the targeted area was observed for ASD, regardless of equipped nozzle types, compared to a ride-on sprayer. Drift also occurred at least 3 times more for ASD application than for a ride-on sprayer and a spray gun sprayer. Using smooth crabgrass infestation annotated from aerial images could not consistently resolve the spatial variability evident in UV-fluorescent imagery presumably due to the innate variability in weed populations. Analysis using SprayDAT revealed insights into factors affecting ASD spray deposition, such as operational height impacting drift, effective swath width, and herbicide efficacy, highlighting the tool's utility in optimizing aerial herbicide applications in turfgrass management. Data suggest that the lowest ASD operational height should be employed to partially mitigate drift and droplet evaporation while improving weed control. Lower operational heights, however, reduce effective swath width and increase heterogeneity of the deposition pattern. Future research should evaluate possible engineering controls for these problems.
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    Cover crop termination options and application of remote sensing for evaluating termination efficiency
    Kumar, Vipin; Singh, Vijay; Flessner, Michael L.; Haymaker, Joseph; Reiter, Mark S.; Mirsky, Steven B. (Public Library of Science, 2023-04-20)
    Efficient termination of cover crops is an important component of cover crop management. Information on termination efficiency can help in devising management plans but estimating herbicide efficacy is a tedious task and potential remote sensing technologies and vegetative indices (VIs) have not been explored for this purpose. This study was designed to evaluate potential herbicide options for the termination of wheat (Triticum aestivum L.), cereal rye (Secale cereale L.), hairy vetch (Vicia villosa Roth.), and rapeseed (Brassica napus L.), and to correlate different VIs with visible termination efficiency. Nine herbicides and one roller-crimping treatment were applied to each cover crop. Among different herbicides used, glyphosate, glyphosate + glufosinate, paraquat, and paraquat + metribuzin provided more than 95% termination for both wheat and cereal rye 28 days after treatment (DAT). For hairy vetch, 2,4-D + glufosinate and glyphosate + glufosinate, resulted in 99 and 98% termination efficiency, respectively, followed by 2,4-D + glyphosate and paraquat with 92% termination efficiency 28 DAT. No herbicide provided more than 90% termination of rapeseed and highest control was provided by paraquat (86%), 2,4-D + glufosinate (85%), and 2,4-D + glyphosate (85%). Roller-crimping (without herbicide application) did not provide effective termination of any cover crop with 41, 61, 49, and 43% termination for wheat, cereal rye, hairy vetch, and rapeseed, respectively. Among the VIs, Green Leaf Index had the highest Pearson correlation coefficient for wheat (r = -0.786, p = <0.0001) and cereal rye (r = -0.804, p = <0.0001) with visible termination efficiency rating. Whereas for rapeseed, the Normalized Difference Vegetation Index (NDVI) had the highest correlation coefficient (r = -0.655, p = <0.0001). The study highlighted the need for tankmixing 2,4-D or glufosinate with glyphosate for termination instead of blanket application of glyphosate alone for all crops including rapeseed and other broadleaf cover crops.
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    Critical updates for the 2020-2021 Mid-Atlantic Commercial Vegetable Recommendations
    Kuhar, Thomas P.; Rieter, Mark S. |deout, Steven Lewis; RSingh, Vijaye L.; Singh, Vijay (Virginia Cooperative Extension, 2021-03-01)
    Updates to the 2020-2021 Mid-Atlantic Commercial Vegetable Recommendations
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    Detection of Italian Ryegrass in Wheat and Prediction of Competitive Interactions Using Remote-Sensing and Machine-Learning Techniques
    Sapkota, Bishwa; Singh, Vijay; Neely, Clark; Rajan, Nithya; Bagavathiannan, Muthukumar V. (MDPI, 2020-09-13)
    Italian ryegrass (Lolium perenne ssp. multiflorum (Lam) Husnot) is a troublesome weed species in wheat (Triticum aestivum) production in the United States, severely affecting grain yields. Spatial mapping of ryegrass infestation in wheat fields and early prediction of its impact on yield can assist management decision making. In this study, unmanned aerial systems (UAS)-based red, green and blue (RGB) imageries acquired at an early wheat growth stage in two different experimental sites were used for developing predictive models. Deep neural networks (DNNs) coupled with an extensive feature selection method were used to detect ryegrass in wheat and estimate ryegrass canopy coverage. Predictive models were developed by regressing early-season ryegrass canopy coverage (%) with end-of-season (at wheat maturity) biomass and seed yield of ryegrass, as well as biomass and grain yield reduction (%) of wheat. Italian ryegrass was detected with high accuracy (precision = 95.44 ± 4.27%, recall = 95.48 ± 5.05%, F-score = 95.56 ± 4.11%) using the best model which included four features: hue, saturation, excess green index, and visible atmospheric resistant index. End-of-season ryegrass biomass was predicted with high accuracy (R2 = 0.87), whereas the other variables had moderate to high accuracy levels (R2 values of 0.74 for ryegrass seed yield, 0.73 for wheat biomass reduction, and 0.69 for wheat grain yield reduction). The methodology demonstrated in the current study shows great potential for mapping and quantifying ryegrass infestation and predicting its competitive response in wheat, allowing for timely management decisions.
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    Evaluation Of Current Policies on the use of Unmanned Aerial Vehicles in Indian Agriculture
    Singh, Vijay; Bagavathiannan, Muthukumar V.; Chauhan, Bhagirath Singh; Singh, Samar (Current Science Association, 2019-07-10)
    Unmanned aerial vehicles (UAVs), commonly called ‘drones’, have enormous potential for technological advances in many sectors including agriculture. The recent revision in UAV policy by the Directorate General of Civil Aviation (DGCA), India, can impact the pace of research and development in machine vision capabilities in the country. Several other countries that have framed UAV policy previously, are continuously bringing changes to the existing framework to make it more user friendly. India can learn from those changes and bring out a comprehensive update to foster a broader application of these tools in agriculture. This policy review provides suggestions and solutions for increasing licensing centres, limiting UAV speed and weight for safer flights and including aerial pesticide applications in UAV permits to revolutionize the multibillion-dollar agriculture industry. This article has also examines the current UAV regulations in four other countries.
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    Evaluation of the quantity and composition of sugars and lipid in the juice and bagasse of lipid producing sugarcane
    Huang, Haibo; Moreau, Robert A.; Powell, Michael J.; Wang, Zhaoqin; Kannan, Baskaran; Altpeter, Fredy; Grennan, Aleel K.; Longe, Stephen P.; Singh, Vijay (2017-04)
    Biodiesel production in the U.S. from vegetable oils has increased substantially during the past decade. However, its further increase is limited by the low amounts of oil produced per hectare from temperate oilseed crops. Recently novel transgenic sugarcane has been developed to accumulate both sugars and lipids in stems, making it a promising dual-purpose feedstock to produce both ethanol and biodiesel. In this study, two lines of the transgenic lipid producing sugarcane (lipid-cane) and the non-transformed sugarcane were characterized and processed. The total lipid concentrations were 0.7%, 0.9% and 1.3% for the non-transformed sugarcane and lipid-cane lines19B and 25 C, respectively. Lipid composition analysis showed that about 31-33% of the total lipids were triacylglycerols, main feedstock for biodiesel production, for the lipid-cane samples, while this value was only 5% for the non-transformed sugarcane. By processing the sugarcane stems with a juicer, about 90% of the sugars and 60% of the lipids were extracted with juice. The extracted sugars in juice were fermented to ethanol and the lipids were later recovered from the fermented juice using organic solvents. The recovered lipids from the fermented juice were 0.3, 0.5 and 0.8 g/100 g dry stem for the non-transformed sugarcane and lipid-cane lines 19B and 25 C, respectively. This study proved the concept of the lipid and sugar coproduction from the novel lipid-cane, which have a potential to make a large-scale replacement of fossil derived fuel without unrealistic demands on land area.
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    Exploring the potential of chaff lining in Virginia wheat and soybean production.
    Spoth, Matthew Patrick (Virginia Tech, 2023-02-15)
    Harvest weed seed control (HWSC) methods concentrate, remove, or destroy weed seeds captured by the combine during harvest. Furthermore, chaff lining uses a chute fitted on the back of a combine to concentrate chaff and weed seed therein into a narrow line. Since chaff amount increases with crop yield, studies aimed to determine how varying crop yield and the associated chaff amount will affect chaff lining control of select weed species, while also examining subsequent crop performance. Objective 1 of this work focused on wheat chaff lining (WCL), and objective 2 studied soybean chaff lining (SCL). Weed species of interest included wild mustard (Sinapis arvensis L.) and Italian ryegrass (Lolium perenne ssp. multiflorum L. Husnot) in WCL and Palmer amaranth (Amaranthus palmeri S.) and common ragweed (Ambrosia artemisiifolia L.) subject to SCL. Each weed species was evaluated in separate experiments, and the SCL experiment included an additional factor of with and without a cereal rye cover crop treatment. Chaff lines mimicked harvest across a range of wheat and soybean yields, with equal weed seed additions (based on existing fecundity and seed shatter phenology data) to each chaff line. A conventional harvest (control) and an outside-the-chaff-line treatment were included, where total fecundity or weed seed rain occurring prior to harvest based on weed species were broadcast respectively. Inhibition of crop and weed emergence as a function of yield and the associated chaff amount was also investigated in the greenhouse. Crop yield across treatments at the field scale (accounts for both chaff lines and outside-the-chaff-line), was not affected in double-crop soybean following WCL and full-season soybean following SCL. Field scale wheat yield in WCL compared to conventional harvest was not different, increased, or decreased in 8, 3, and 1 site-years, respectively. WCL reduced total weed emergence over the combined double-crop soybean and winter wheat growing seasons by 43-54% at the field scale. SCL reduced common ragweed emergence in cereal rye by 64% and 85% in 2 of 3 locations across the soybean growing season. The cover crop did not reduce common ragweed emergence while it was growing, but residual mulch in soybean reduced emergence by 39%. No differences were observed in Palmer amaranth emergence during cereal rye growth, however cereal rye decreased total emergence by 41%. In 6 of 7 Palmer amaranth location-years, SCL decreased field scale weed emergence in soybean by 81%. These results indicate chaff may create an unfavorable environment for weed seed emergence. In both WCL and SCL, greater amounts of chaff caused larger reductions in weed emergence. Objective 3 focused on quantifying the above-ground biomass breakdown of soybean plants into chaff, straw, and seed fractions as they are processed and dispensed by various harvesters. Depending on HWSC system, chaff and straw residues may also be destroyed, removed, or concentrated. Therefore, chaff and straw nutrient composition was analyzed to evaluate the nutrient and economic consequences of HWSC. Our results show average soybean harvest index is 0.57:1. Furthermore, chaff and straw residues equal 13.4% and 68.5% of the seed weight, respectively. Using 5-year average fertilizer prices (2017 – 2021), replacement of N, P, K and S in chaff, straw, and the combination of both residues costs USD 1.58, USD 5.88, and USD 7.46, respectively.
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    Field Crops: 2022 Pest Management Guide
    Besancon, Thierry E.; Cahoon, Charlie; Chandran, Rakesh; Currin, John F.; Day, Eric R.; Flessner, Michael; Frame, William Hunter; Frank, Daniel; Hines, Tommy; Johnson, Quintin; Jordan, David; Koehler, Alyssa; Langston, David B.; Lingenfelter, Dwight; Reed, T. David; Singh, Vijay; Taylor, Sally V.; VanGessel, Mark; Vollmer, Kurt; Wallace, John M.; Wilson, James M. (2022-02-03)
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    Herbicide options for effective weed management in dry direct-seeded rice under scented rice-wheat rotation of western Indo-Gangetic Plains
    Singh, Vijay; Jat, Mangi L.; Ganie, Zahoor A.; Chauhan, Bhagirath S.; Gupta, Raj K. (Elsevier, 2016-03-01)
    Farmers' participatory field trials were conducted at Madhuban, and Taraori, the two participatory experimental sites/locations of the Cereal Systems Initiative for South Asia (CSISA), a collaborative project of IRRI and CIMMYT in Karnal district of Haryana, India, during Kharif (wet season) 2010 and 2011. This research aimed to evaluate preemergence (PRE) and postemergence (POST) herbicides for providing feasible and economically viable weed management options to farmers for predominant scented rice varieties. Treatments with pendimethalin PRE fb bispyribac-sodium + azimsulfuron POST had lower weed biomass at 45 days after sowing (DAS). At Madhuban, highest grain yield of scented basmati rice (3.43 t ha(-1)) was recorded with the sequential application of pendimethalin PRE fb bispyribac-sodium + azimsulfuron POST. However, at Taraori, yields were similar with pendimethalin or oxadiargyl PRE fb bispyribac-sodium and/or azimsulfuron POST. Applying oxadiargyl by mixing with sand onto flooded field was less effective than spray applications in non-flooded field. The benefit-cost ratio of rice crop was higher with herbicide treatments at both sites as compared with the non-treated weed-free check except single PRE and POST applications and sequential application of oxadiargyl PRE fb oxadiargyl PRE. In a separate experiment conducted at Nagla and Taraori sites, scented rice cultivars' ('CSR 30' and 'Pusa 1121') tolerance to three rates of azimsulfuron (15, 25, and 35 g ai ha(-1)) was evaluated over two years (2010 and 2011). CSR 30 (superfine, scented) was more sensitive to higher rates (35 g ai ha(-1)) of azimsulfuron as compared to Pusa 1121 (fine, scented). Crop injuries were 8 and 28% in case of CSR 30; 5 and 15% in Pusa 1121 when applied with azimsulfuron 25 and 35 g ai ha(-1), respectively. Azimsulfuron applied at 35 g ai ha(-1) reduced yield in both cultivars but in CSR 30 yield reduction was twofold (11.5%) as that of Pusa 1121 (5.2%).
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    Impact of Futuristic Climate Variables on Weed Biology and Herbicidal Efficacy: A Review
    Kumar, Vipin; Kumari, Annu; Price, Andrew J.; Bana, Ram Swaroop; Singh, Vijay; Bamboriya, Shanti Devi (MDPI, 2023-02-15)
    Our changing climate will likely have serious implications on agriculture production through its effects on food and feed crop yield and quality, forage and livestock production, and pest dynamics, including troublesome weed control. With regards to weeds, climatic variables control many plant physiology functions that impact flowering, fruiting, and seed dormancy; therefore, an altered climate can result in a weed species composition shift within agro-ecosystems. Weed species will likely adapt to a changing climate due to their high phenotypic plasticity and vast genetic diversity. Higher temperatures and CO2 concentrations, and altered moisture conditions, not only affect the growth of weeds, but also impact the effectiveness of herbicides in controlling weeds. Therefore, weed biology, growth characteristics, and their management are predicted to be affected greatly by changing climatic conditions. This manuscript attempted to compile the available information on general principles of weed response to changing climatic conditions, including elevated CO2 and temperature under diverse rainfall patterns and drought. Likewise, we have also attempted to highlight the effect of soil moisture dynamics on the efficacy of various herbicides under diverse agro-ecosystems.
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    Influence of Cover Crop Termination Timing on its Volunteers and Weed Suppression
    Kumar, Vipin (Virginia Tech, 2023-01-19)
    Cover crops are widely planted in the mid-Atlantic region for their environmental and agronomic benefits, but incomplete or delayed termination can lead to cover crops becoming weeds in the subsequent cash crop, known as volunteers. Studies were conducted from 2020-2022 to evaluate the effect of four commonly grown cover crop species, winter wheat (Triticum aestivum L.), cereal rye (Secale cereal L.), hairy vetch (Vicia villosa Roth), and rapeseed (Brassica napus L.), and four termination timings; 28, 14, 5, and 1 days before corn planting (DBP). Results indicated volunteerism was only an issue with rapeseed. Delaying rapeseed termination resulted in 0, 5, 12, and 22 volunteer plants m-2 at 28, 14, 5, and 1 DBP in corn. In order to manage these rapeseed volunteers, herbicide evaluations were conducted and indicated that atrazine, isoxaflutole, metribuzin, and pyroxasulfone resulted in 92-94% control when applied preemergence. Similarly, atrazine and glyphosate provided 99% rapeseed control and glufosinate resulted in 89% control when applied postemergence. Therefore, volunteers can easily be controlled with commonly used herbicides in corn. Studies were also conducted to evaluate the benefits of these cover crops, which have the potential to overcome the aforementioned risks. Results indicate that hairy vetch produced the most biomass and provided greater control of summer annual grasses, small-seeded broadleaf and large-seeded broadleaf weeds than other cover crops. Biomass accumulation and extent of weed control increased with delaying cover crop termination. Corn yield was greatest following hairy vetch and was least in rapeseed plots. Termination of cover crops 14 DBP planting increased corn yield by 12%; whereas termination at 1 DBP decreased corn yield by 15% as compared to no cover crop-no till plots. Effective termination of cover crops is an important management consideration and information on termination efficiency can help in devising management plans. In order to assist managers by evaluating cover crop termination efficiency, studies were conducted to evaluate selective and non-selective herbicides and a roller crimper for correlating vegetative indices with visible termination efficiency. Among vegetative indices, the Green Leaf Index had the highest Pearson correlation coefficient for wheat (r = -0.79, p = <0.0001) and cereal rye (r = -0.80, p = <0.0001) with visible termination efficiency. Whereas, for rapeseed, Normalized Difference Vegetation Index (NDVI) had the highest correlation coefficient (r = -0.66, p = <0.0001). However, for hairy vetch none of the vegetative indices correlated significantly with visible termination efficiency. While further research is necessary, remote sensing technologies may help in devising management plans by increasing crop scouting efficiency.
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    Mapping and Estimating Weeds in Cotton Using Unmanned Aerial Systems-Borne Imagery
    Sapkota, Bishwa; Singh, Vijay; Cope, Dale; Valasek, John; Bagavathiannan, Muthukumar V. (MDPI, 2020-06-16)
    In recent years, Unmanned Aerial Systems (UAS) have emerged as an innovative technology to provide spatio-temporal information about weed species in crop fields. Such information is a critical input for any site-specific weed management program. A multi-rotor UAS (Phantom 4) equipped with an RGB sensor was used to collect imagery in three bands (Red, Green, and Blue; 0.8 cm/pixel resolution) with the objectives of (a) mapping weeds in cotton and (b) determining the relationship between image-based weed coverage and ground-based weed densities. For weed mapping, three different weed density levels (high, medium, and low) were established for a mix of different weed species, with three replications. To determine weed densities through ground truthing, five quadrats (1 m × 1 m) were laid out in each plot. The aerial imageries were preprocessed and subjected to Hough transformation to delineate cotton rows. Following the separation of inter-row vegetation from crop rows, a multi-level classification coupled with machine learning algorithms were used to distinguish intra-row weeds from cotton. Overall, accuracy levels of 89.16%, 85.83%, and 83.33% and kappa values of 0.84, 0.79, and 0.75 were achieved for detecting weed occurrence in high, medium, and low density plots, respectively. Further, ground-truthing based overall weed density values were fairly correlated (r2 = 0.80) with image-based weed coverage assessments. Among the specific weed species evaluated, Palmer amaranth (Amaranthus palmeri S. Watson) showed the highest correlation (r2 = 0.91) followed by red sprangletop (Leptochloa mucronata Michx) (r2 = 0.88). The results highlight the utility of UAS-borne RGB imagery for weed mapping and density estimation in cotton for precision weed management.
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    Morphophysiological diversity and its association with herbicide resistance in Echinochloa ecotypes
    Liu, Rui; Singh, Vijay; Abugho, Seth; Lin, Hao-Sheng; Zhou, Xin-Gen; Bagavathiannan, Muthukumar V. (Cambridge University Press, 2021-10-01)
    The genus Echinochloa constitutes some of the most prominent weed species found in rice (Oryza sativa L.) production worldwide. The taxonomy of Echinochloa is complex due to its morphological variations. The morphophysiological diversity and taxonomic characteristics of Echinochloa ecotypes infesting rice fields in Texas are unknown. A total of 54 Echinochloa ecotypes collected during late-season field surveys in 2015 and 2016 were characterized in a common garden in 2017. Plants were characterized for 14 morphophysiological traits, including stem angle; stem color; plant height; leaf color; leaf texture; flag leaf length, width, and angle; days to flowering; panicle length; plant biomass; seed shattering; seed yield; and seed dormancy. Principal component analysis indicated that 4 (plant height, flag leaf length, seed shattering, and seed germination) of the 14 phenological traits characterized here had significantly contributed to the overall morphological diversity of Echinochloa spp. Results showed wide interpopulation diversity for the measured traits among the E. colona ecotypes, as well as diverse intrapopulation variability in all three Echinochloa species studied, including barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.], junglerice [Echinochloa colona (L.) Link], and rough barnyardgrass [Echinochloa muricata (P. Beauv.) Fernald]. Taxonomical classification revealed that the collection consisted of three Echinochloa species, with E. colona being the most dominant (96%), followed by E. crus-galli (2%), and E. muricata (2%). Correlation analysis of morphophysiological traits and resistance status to commonly used preemergence (clomazone, quinclorac) and postemergence herbicides (propanil, quinclorac, imazethapyr, and fenoxaprop-ethyl) failed to show any significant association. Findings from this study provided novel insights into the morphophysiological characteristics of Echinochloa ecotypes in rice production in Texas. The morphological diversity currently present in Echinochloa ecotypes could contribute to their adaptation to selection pressure imposed by different management tools, emphasizing the need for a diversified management approach to effectively control this weed species.
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    Occurrence and management of herbicide resistance in annual vegetable production systems in North America
    Boyd, Nathan S.; Moretti, Marcelo L.; Sosnoskie, Lynn M.; Singh, Vijay; Kanissery, Ramdas; Sharpe, Shaun; Besançon, Thierry; Culpepper, Stanley; Nurse, Robert; Hatterman-Valenti, Harlene; Mosqueda, Elizabeth; Robinson, Darren; Cutulle, Matthew; Sandhu, Ravneet (Cambridge University Press, 2022-09-05)
    Herbicide resistance has been studied extensively in agronomic crops across North America but is rarely examined in vegetables. It is widely assumed that the limited number of registered herbicides combined with the adoption of diverse weed management strategies in most vegetable crops effectively inhibits the development of resistance. It is difficult to determine whether resistance is truly less common in vegetable crops or whether the lack of reported cases is due to the lack of resources focused on detection. This review highlights incidences of resistance that are thought to have arisen within vegetable crops. It also includes situations in which herbicide-resistant weeds were likely selected for within agronomic crops but became a problem when vegetables were grown in sequence or in adjacent fields. Occurrence of herbicide resistance can have severe consequences for vegetable growers, and resistance management plans should be adopted to limit selection pressure. This review also highlights resistance management techniques that should slow the development and spread of herbicide resistance in vegetable crops.
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    Prevention and Control of Palmer Amaranth in Cotton
    Flessner, Michael; Singh, Vijay; Frame, William Hunter, 1985-; Greene, Wykle (Virginia Cooperative Extension, 2020-09-22)
    Palmer amaranth (Amaranthus palmeri), a member of the "pigweed" family, is one of the most troublesome weeds in many southern row crops. Seed can germinate all season and plants can grow to over 6 feet in height. Plants have either male flowers that shed pollen or female flowers that can produce up to 600,000 seed per plant. One Palmer amaranth per 30 foot of row can reduce cotton yield by 6 to 12%.