Flood Timing and Flood Loss Impact on Effectiveness of Florpyrauxifen-benzyl Coated on Urea in Rice

Abstract

Florpyrauxifen-benzyl applications generated complaints and concerns around rice injury and off-target movement to soybean after the commercial launch in 2018. A precise application method for florpyrauxifen-benzyl was imperative for its continued use. Experiments were conducted in 2020 and 2021 to evaluate rice weed control as influenced by preflood application interval and flood loss following florpyrauxifen-benzyl at 30 g ai ha-1 applied as a spray or coated on urea. In the preflood application experiment, coating florpyrauxifen-benzyl on urea and applying it the day of flood establishment, 5, and 10 d prior to flooding (DPTF) resulted in lower yellow nutsedge, broadleaf signalgrass, and barnyardgrass control than when the herbicide was spray at 3 and 5 wk after final treatment (WAFT). Coating florpyrauxifen-benzyl on urea only provided 61 to 63% yellow nutsedge control at 3 and 5 WAFT, which was 35 to 37 percentage points lower than when spray applied at 5 or 10 DPTF. Likewise, rice yields following applications of florpyrauxifen-benzyl coated on urea were 1200 kg ha-1 less than yields following spray applications. Florpyrauxifen-benzyl coated on urea and clomazone provided lower levels of weed control than spraying the herbicide, suggesting an explanation for the yield losses. The timing of flood loss experiment suggested that when florpyrauxifen-benzyl coated on urea at 30 g ai ha-1 was applied preflood and flood was relinquished at 2 hours, 24 hours, and 7 d after flood establishment, hemp sesbania and yellow nutsedge control were not affected. However, loss of floodwater 2 hours after flood establishment resulted in lower barnyardgrass control than when the flood was lost 24 hours and 7 d after flooding. Generally, the period between a herbicide application and flooding completion should be minimized to aid in weed control. These results indicate the importance of maintaining a flood for weed control and nutrient management.