Large-scale evaluation of 2,4-D choline off-target movement and injury in 2,4-D-susceptible soybean

Rodrigo Werle,Sarah Striegel,Ahmadreza Mobli,Nicholas Arneson,Ryan Dewerff,Maxwel Oliveira,Ashli Brown

doi:10.1017/wet.2021.62

Abstract

AbstractEnlist E3TM soybean cultivars permit over-the-top application of labeled glyphosate, glufosinate, and 2,4-D choline products. Increased Enlist E3TM trait adoption and use of 2,4-D choline postemergence across U.S. soybean production systems raise concerns regarding potential for 2,4-D off-target movement (OTM). A large-scale drift experiment was established near Sun Prairie, WI, and Arlington, WI, in 2019 and 2020, respectively. A 2,4-D-resistant soybean cultivar was planted in the center of the field (∼3 ha), while the surrounding area was planted with a 2,4-D-susceptible cultivar. An application of 785 ae ha−1 2,4-D choline plus 834 g ae ha−1 glyphosate was completed within the center block at R2 and V6 growth stages on August 1, 2019, and July 3, 2020, respectively. Filter papers were placed in-swath and outside of the treated area in one upwind transect and three downwind transects to estimate particle deposition. Low-volume air samplers ran for the 0.5-h to 48-h period following application to estimate 2,4-D air concentration. Injury to 2,4-D-susceptible soybean was assessed 21 d after treatment (0% to 100% injury). The 2,4-D deposition in-swath was 9,966 and 5,727 ng cm−2 in 2019 and 2020, respectively. Three-parameter log-logistic models estimated the distance to 90% reduction in 2,4-D deposition (D90) to be 0.63 m and 0.90 m in 2019 and 2020, respectively. In 2020, the 2,4-D air concentration detected was lower for the upwind (0.395 ng m−3) than the downwind direction (1.34 ng m−3), although both were lower than the amount detected in-swath (4.01 ng m−3). No soybean injury was observed in the downwind or upwind directions. Our results suggest that 2,4-D choline applications following label recommendations pose little risk to 2,4-D-susceptible soybean cultivars; however, further work is needed to understand 2,4-D choline OTM under different environmental conditions and the presence of other susceptible crops.

Highlights

Since the 1940s, 2,4-dichlorophenoxyacetic-acid (2,4-D) has been used as an active ingredient in more than 1,500 commercial herbicide products worldwide (Islam et al 2018)
Growers may select a formulation based on weed species present and the potential for off-target movement (OTM) toward neighboring susceptible crops (Aquino et al 2007; Nice et al 2004)
The treated area (3.0 and 2.9 ha at the Sun Prairie and Arlington locations, respectively) was planted with a 2,4-D-resistant soybean cultivar and the area bordering the treated area was planted with a 2,4-D-susceptible soybean cultivar (Table 1)

Summary

Introduction

Since the 1940s, 2,4-dichlorophenoxyacetic-acid (2,4-D) has been used as an active ingredient in more than 1,500 commercial herbicide products worldwide (Islam et al 2018). While the labels of 2,4-D choline products contain detailed application requirements to mitigate particle drift, including carrier volume range (94 to 140 L ha−1), spray nozzles that produce coarse to ultra-coarse droplets (>326 μm), low wind speed conditions (

Results

Conclusion