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

Abstract

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 non-target 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), which will be abbreviated as CR3841, CR4748, AG4135, and ST40B, respectively. Soybean were treated with 5.6 g ae ha-1 of dicamba at V3 and R1. 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 ‘Asgrow AG4135RR2Y’ and ‘Stine 40BA02’. Dicamba application at R1 resulted in the greatest injury to ‘Stine 40BA02’ 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 ‘Credenz 4748LL’, and the greatest in ‘Stine 40BA02’. Varieties with greater injury at senescence generally yielded less than other varieties.

Non‐dicamba‐resistant soybean response to multiple dicamba applications

“…Correlations obtained in this trial were similar to those obtained by Meyeres (2020) and Meyeres et al. (2021). Previous literature has stated that primary yield components, such as seeds m −2 , pods m −2 , and nodes m −2 should be characterized to understand the magnitude of which dicamba exposures on non‐DR soybean impact yield (Robinson et al., 2013).…”

“…No significant differences were observed among site-year, rate, and timing of application for germination, emergence, number of offspring injured, offspring visual injury, and offspring height (data not shown). Injury was not observed in the offspring, which is similar to results reported by Meyeres (2020) and Meyeres et al (2021). Previous literature has observed reduced germination, emergence, and vigor and injury in the offspring of soybean treated with dicamba and that an increase response severity as dicamba rate increased (Auch & Arnold, 1978;Jones et al, 2019;Thompson & Egli, 1973;Wax et al, 1969).…”

“…ha −1 dicamba at V3 and V7. Meyeres (2020) and Meyeres et al (2021) reported no significant effects when soybean were exposed to 5.6 g a.e. ha −1 dicamba at V3 and R1.…”

“…This variety was selected because it is commonly grown in eastern Kansas, is high yielding, and was suspected to exhibit high susceptibility to dicamba in comparison to similar varieties by an industry contact. However, Meyeres (2020) and Meyeres et al (2021) reported no differences in sensitivity when compared to other popular varieties in eastern Kansas and found that timing of dicamba exposure had more influence on soybean response than variety. Soil properties are summarized in Table 1.…”

“…The effect on offspring seems to be variable as Meyeres et al. (2021) observed no negative effects on offspring.…”