Effect of carrier volume and spray quality on glyphosate‐resistant soybean response to sublethal dicamba exposure

Abstract

BACKGROUND Field experiments were conducted across three sites in Mississippi in 2018 to evaluate carrier volume and spray quality effects on glyphosate‐resistant soybean response to dicamba. Treatments consisted of dicamba (5.6 g a.e. ha−1) plus glyphosate (8.7 g a.e. ha−1) applied to soybean at R1 using 140, 105, 70, 35, 14, or 7 L ha−1. Each carrier volume was applied with TT11002 and XR110015 nozzles which resulted in Fine and Coarse spray qualities, respectively. A colorimetric dye was included in spray solutions to quantify spray coverage of each treatment. RESULTS Spray coverage decreased with carrier volume and ranged from 21% to 3%. Conversely, soybean injury increased as carrier volume decreased. Soybean height 14 days after treatment (DAT) was reduced 34% to 37% from carrier volumes of 70 to 140 L ha−1; however, carrier volumes of 14 and 7 L ha−1 resulted in 45% height reductions. By 28 DAT soybean height was similar among volumes of 35 to 140 L ha−1 (39% to 42% reduction); however, volumes of 14 and 7 L ha−1 resulted in 46% and 51% reductions, respectively. Grain yield was reduced 14% from treatment at 140 L ha−1 and reductions increased with decreased carrier volume to 41% loss at 7 L ha−1. Averaged across carrier volumes, Fine and Coarse sprays caused 30% and 26% yield loss, respectively. CONCLUSION These data suggest that carrier volume profoundly affects soybean response to dicamba. Therefore, soybean response to sublethal dicamba doses applied at a constant carrier volume may not reflect physical drift exposure. © 2021 Society of Chemical Industry

Soybean dose–response to 2,4‐D and dicamba at vegetative and reproductive growth stages

“…Moreover, it is important to note that all data were derived from treatments that were applied using a constant application volume. This method results in highly dilute solutions that more reflect tank contamination exposures than spray drift or vapor exposure, which potentially result in exacerbated responses 31,66,67 . Therefore, further investigations into exposure route effects on dose–response of soybean and dicamba are warranted.…”

“…This method results in highly dilute solutions that more reflect tank contamination exposures than spray drift or vapor exposure, which potentially result in exacerbated responses. 31,66,67 Therefore, further investigations into exposure route effects on doseresponse of soybean and dicamba are warranted. Lastly, hormesis effects on plant height of various extents were documented from low-dose dicamba exposure in greenhouse experiments.…”

“…9,19,28 However, visually evaluated injury is considered subjective according to the evaluator and soybean response to dicamba can be variable depending on environmental conditions and exposure type. 21,22,[29][30][31] Soybean injury from dicamba and 2,4-D is often proportionally greater than yield loss as the relationship is not linear. 19,32 Previous research indicated that dicamba doses of 2.3 g ha −1 or greater can cause apical meristem death in soybean, but plants often recover to some extent by producing additional branches.…”

“…Prediction of yield loss after soybean exposure to 2,4‐D or dicamba has been previously attempted with plant height and visually evaluated soybean injury as indicators 9,19,28 . However, visually evaluated injury is considered subjective according to the evaluator and soybean response to dicamba can be variable depending on environmental conditions and exposure type 21,22,29–31 . Soybean injury from dicamba and 2,4‐D is often proportionally greater than yield loss as the relationship is not linear 19,32 .…”

Design of a Novel Hapten and Development of a Sensitive Monoclonal Immunoassay for Dicamba Analysis in Environmental Water Samples

“…Dicambaa chlorinated derivative of o-anisic acidis an efficient, lowcost post-emergence herbicide that was first registered in 1967. Nowadays, the use of this classic pesticide has increased worldwide due to the commercialization of genetically modified dicamba-resistant soybean, corn, and cotton plants by Monsanto as a solution for farmers facing weed resistance to glyphosate (Werle et al, 2018;Singh et al, 2020;Sperry et al, 2021). Dicamba is included in the formulation of different brand names, such as Dianat, Banvel, Diablo, Oracle, and Vanquish, and it is commonly applied on corn and crops of Triticeae sp.…”