Droplet size impact on lactofen and acifluorfen efficacy for Palmer amaranth (Amaranthus palmeri) control

Abstract

Herbicide applications performed with pulse width modulation (PWM) sprayers to deliver specific spray droplet sizes could maintain product efficacy, minimize potential off-target movement, and increase flexibility in field operations. Given the continuous expansion of herbicide-resistant Palmer amaranth populations across the southern and midwestern United States, efficacious and cost-effective means of application are needed to maximize Palmer amaranth control. Experiments were conducted in two locations in Mississippi (2016, 2017, and 2018) and one location in Nebraska (2016 and 2017) for a total of 7 site-years. The objective of this study was to evaluate the influence of a range of spray droplet sizes [150 (Fine) to 900 μm (Ultra Coarse)] on lactofen and acifluorfen efficacy for Palmer amaranth control. The results of this research indicated that spray droplet size did not influence lactofen efficacy on Palmer amaranth. Palmer amaranth control and percent dry-biomass reduction remained consistent with lactofen applied within the aforementioned droplet size range. Therefore, larger spray droplets should be used as part of a drift mitigation approach. In contrast, acifluorfen application with 300-μm (Medium) spray droplets provided the greatest Palmer amaranth control. Although percent biomass reduction was numerically greater with 300-μm (Medium) droplets, results did not differ with respect to spray droplet size, possibly as a result of initial plant injury, causing weight loss, followed by regrowth. Overall, 900-μm (Ultra Coarse) droplets could be used effectively without compromising lactofen efficacy on Palmer amaranth, and 300-μm (Medium) droplets should be used to achieve maximum Palmer amaranth control with acifluorfen.

Nozzle Selection and Adjuvant Impact on the Efficacy of Glyphosate and PPO-Inhibiting Herbicide Tank-Mixtures

“…Smaller droplets from non-air inclusion nozzles for POST herbicide applications at a constant volume have been reported to be more effective than larger droplets [24]. In contrast, many studies have reported no differences in weed control regarding droplet size when PPO-inhibiting herbicides [11,25,26,28,35] were applied to several weed species. Conflicting results found in the literature shows that herbicide efficacy is not solely dependent on droplet size.…”

Effect of single or sequential POST herbicide applications on seed production and viability of glyphosate-resistant Palmer amaranth (Amaranthus palmeri) in dicamba- and glyphosate-resistant soybean

“…Mayo et al (1995) reported a similar decline in Palmer amaranth control from 35% to 18% and 99% to 56% when acifluorfen and lactofen were applied at 14 and 28 d after soybean planting, respectively. Furthermore, Franca et al (2020) reported 52%-67% control of Palmer amaranth with lactofen or acifluorfen when plants were 15 cm tall at the time of application. Similarly, Gizotti de Moraes (2018) reported 40% and 54% control of Palmer amaranth with fomesafen and lactofen, respectively, when plants were at flowering stage (15-58 cm tall).…”

Cotton (Gossypium hirsutum) Response to Plant Protection Products using Different Spray Nozzles

“…Spray droplet size can affect coverage of weeds and subsequent control. However, efficacy of herbicides is not always affected and can be variable depending upon a range of factors [7][8][9][10][11][12][13][14][15]. Efficacy of dicamba, glufosinate, and glyphosate was not affected by droplet size [8,11,12].…”