Evaluating Injury Risk Caused by Potential Drift of Florpyrauxifen‐Benzyl or Quinclorac in Corn

Abstract

Of relevance to the off‐target movement of herbicides in Arkansas is the drift of rice herbicides in the state’s agricultural landscape, where aerial application of herbicides is common, raising the prima facie question of the risk of damage to other sensitive crops. The aim of this study was to evaluate the response of corn to postemergence applications of florpyrauxifen‐benzyl or quinclorac, which were applied directly to the crop at low rates (0.78 or 1.56 to 12.5% of the normal use rate for labeled crops). This was investigated through three site‐year field experiments conducted in Fayetteville (2020 and 2021) and Tillar (2020), Arkansas. Injury and yield response varied among site‐years. No corn injury was visible at the Tillar site. At the Fayetteville site in 2020, florpyrauxifen‐benzyl rates caused an average injury of 5% and 6% 2 and 4 wk after application (WAA), respectively. The 12.5% rate in 2021 caused a greater injury (7% injury) compared to other lower rates 2 WAA and such a response departed from linearity to stochasticity 4 WAA. Compared to the nontreated control, the 6.25% rate caused nearly 20% yield reduction at the Fayetteville site in 2020, and the 12.5% rate caused a 10% yield reduction at the Tillar site. The quinclorac rate of 12.5% at the Fayetteville site in 2020 caused an average of 7% injury‐2 WAA and <5% injury when averaged across the other rates, or 4 WAA. The injury was more differentiated in 2021, particularly with the 12.5% rate (>20% injury) from the average injury of 5% with the other lower rates 2 WAA; the injury remained similar or slightly recovered 4 WAA. Compared to the nontreated control, quinclorac rates caused an average yield reduction of <5% at the Fayetteville site in 2020, whereas the 12.5% rate caused nearly 20% and 10% yield reductions at the Fayetteville site in 2021 and at the Tillar site, respectively.