Row Crop Sensitivity to Low Rates of Foliar-Applied Florpyrauxifen-benzyl

Abstract

In a greenhouse experiment, soybean, cotton, corn, grain sorghum, and sunflower were subjected to 1/10 (3 g ai ha-1), 1/100 (0.3 g ai ha-1), or 1/500 (0.06 g ai ha-1) of the 1X rate of florpyrauxifen-benzyl. Visible injury 14 days after treatment (DAT) was the greatest with soybean (96%) when exposed to the highest drift rate of 1/10x or 3 g ai/ha-1 of florpyrauxifen-benzyl and was significantly higher than all other crops and drift rates. Cotton and sunflower were also injured 85 and 83%, respectively, by the 1/10x rate but had less injury when a 1/100x or 1/500x rate was applied (injury ranging from 9 to 33%). It was concluded that the negative effects on soybean, cotton, and sunflower primarily resulted from exposure to the highest rate tested (1/10x) and only soybean expressed negative effects even at the lower rate of 1/100x. A field study was also conducted to (1) evaluate the sensitivity of soybean to low concentrations of florpyrauxifen-benzyl during vegetative and reproductive development and (2) compare soybean injury and yield following applications of florpyrauxifen-benzyl and dicamba across various growth stages and concentrations. Soybean plants were treated with 1/10, 1/20, 1/40, 1/80, 1/160, 1/320, or 1/640 of the 1X rate of florpyrauxifen-benzyl (30 g ai/ ha-1) or dicamba (560 g ae ha-1) at the V3 and R1 growth stage. Florpyrauxifen-benzyl applied at a rate of 1/10 to 1/40X caused foliar injury and subsequent height reduction. In comparison, dicamba applied at the same rates caused slightly less injury and growth reductions. As rate of florpyrauxifen-benzyl decreased from 1/10 to 1/640X, the level of soybean injury dissipated rather quickly. However, this was not the case with dicamba, as substantial injury was observed with rates as low as 1/640X.