Evaluation of optimal droplet size for control of Palmer amaranth (Amaranthus palmeri) with acifluorfen

Abstract

Acifluorfen is a nonsystemic PPO-inhibiting herbicide commonly used for POST Palmer amaranth control in soybean, peanut, and rice across the southern United States. Concerns have been raised regarding herbicide selection pressure and particle drift, increasing the need for application practices that optimize herbicide efficacy while mitigating spray drift. Field research was conducted in 2016, 2017, and 2018 in Mississippi and Nebraska to evaluate the influence of a range of spray droplet sizes [150 μm (Fine) to 900 μm (Ultra Coarse)], using acifluorfen to create a novel Palmer amaranth management recommendation using pulse width modulation (PWM) technology. A pooled site-year generalized additive model (GAM) analysis suggested that 150-μm (Fine) droplets should be used to obtain the greatest Palmer amaranth control and dry biomass reduction. Nevertheless, GAM models indicated that only 7.2% of the variability observed in Palmer amaranth control was due to differences in spray droplet size. Therefore, location-specific GAM analyses were performed to account for geographical differences to increase the accuracy of prediction models. GAM models suggested that 250-μm (Medium) droplets optimize acifluorfen efficacy on Palmer amaranth in Dundee, MS, and 310-μm (Medium) droplets could sustain 90% of maximum weed control. Specific models for Beaver City, NE, indicated that 150-μm (Fine) droplets provide maximum Palmer amaranth control, and 340-μm (Medium) droplets could maintain 90% of greatest weed control. For Robinsonville, MS, optimal Palmer amaranth control could be obtained with 370-μm (Coarse) droplets, and 90% maximum control could be sustained with 680 μm (Ultra Coarse) droplets. Differences in optimal droplet size across location could be a result of convoluted interactions between droplet size, weather conditions, population density, plant morphology, and soil fertility levels. Future research should adopt a holistic approach to identify and investigate the influence of environmental and application parameters to optimize droplet size recommendations.

Utility of roller wiper applications of dicamba for Palmer amaranth control in soybean

“…The comparative broadcast treatment was made as a salvage treatment when Palmer amaranth reached a 20‐ to 30‐cm height, and a sequential application was made 14 days after final treatment (DAFT). At time of the initial postemergence application, ten Palmer amaranth plants were measured and marked with paint at the base of the plant to aid identification and location of targeted plants at a later date 26–28 . In the case where there were not ten Palmer amaranth plants in the plot, all Palmer amaranth in the plot were measured and marked.…”

Study on Environmental Conditions of Seed Germination and Seedling Growth of Invasive Plant <i>Amaranthus palmeri</i> S. Watson

“…There is a correlation between the viability of Amaranthus palmeri seeds and vigor during artificial aging. After 3 years of naturally existing in soils in Nebraska, vigor of Amaranthus palmeri seeds was found to be less than 10% [19,57]; after 5 months of waterflooding, their vigor was found to be 86% [18]. Therefore, Amaranthus palmeri seeds exhibit a certain tolerance to short-term high temperatures and high humid environments [58,59].…”

“…Its diffusion rate has a tendency to accelerate. Due to its strong adaptability and high genetic variability [16], Amaranthus palmeri can grow on farmlands [17], abandoned lands, in deserts [8], river beds [18], garbage dumps and on roadsides [19]. Invasion risk evaluations have shown that Amaranthus palmeri has a high risk of invasion in North China and Central China [10,20,21], which is the main grain producing area of China.…”

“…Amaranthus palmeri is strongly adaptable to water environments, and its seeds are strongly resistant to water logging. In areas where precipitation is between 130 mm and 730 mm [31], Amaranthus palmeri seeds can still maintain a germination rate of 86% after 5 months of water logging [18]. Amaranthus palmeri can grow normally when soil moisture levels reach 100% of soil field capacity.…”

On-Farm Evaluation of Nozzle Types for Peanut Pest Management Using Commercial Sprayers

“…Typically, smaller droplets produced by non-AI nozzles (XR and XRC) should provide better efficacy for non-systemic pesticides due to increased coverage (Ennis andWilliamson, 1963, McKinlay et al, 1972); however, previous research on effect of nozzle type on pest control (specifically weed control) has reported varying results on correlation between droplet size and the pesticide efficacy (Shaw et al, 2000, Sikkema et al, 2008, Berger et al, 2014. These contrasting results could be attributed to interactions among pesticide efficacy and other factors such as weed species and density, tillage, and soil type (Franca et al, 2020).…”