Response of non-dicamba-resistant soybean (Glycine max) varieties to dicamba

Introduction and rapid adoption of dicamba-resistant (DR) soybean led to an increase of post-emergent applications of dicamba. This resulted in a widespread increase in nontarget dicamba injury to non-DR soybean in 2017. Field studies were conducted in Manhattan, KS, in 2018 and 2019 and in Ottawa, KS, in 2019 to investigate the injury and yield response of soybean varieties with varying herbicide-resistance traits and maturity groups when exposed to dicamba. Four varieties were tested: 'Credenz 3841LL' (glufosinate resistant), 'Credenz 4748LL' (glufosinate resistant), 'Asgrow AG4135RR2Y' (glyphosate resistant), and 'Stine 40BA02' (glyphosate and isoxaflutole resistant), abbreviated as CR3841, CR4748, AG4135, and ST40B, respectively. Soybeans were treated with 5.6 g ae ha(-1) of dicamba at V3 and R1 stages. Percent soybean injury, soybean height, soybean yield and yield components, and injury to offspring were evaluated. Four weeks after treatment (WAT) at V3, the greatest injury was observed in AG4135 and ST4OB. Dicamba application at R1 resulted in the greatest injury to ST4OB both 4 WAT and at senescence. Minimal injury was observed in all varieties treated at V3 at senescence and yield loss was 5% or less. Dicamba application at R1 resulted in 19 to 34% yield loss, with the least yield loss in CR4748, and the greatest in ST4OB. Varieties with greater injury at senescence generally yielded less than other varieties.