Efficacy of Florpyrauxifen-Benzyl on Dioecious Hydrilla and Hybrid Water Milfoil - Concentration and Exposure Time Requirements

This study conducted small-scale trials under various concentration and exposure time (CET) scenarios to determine florpyrauxifen-benzyl activity on dioecious hydrilla and hybrid watermilfoil and determine impact on water stargrass and elodea. Hydrilla treated with 12, 24, or 36 microgram active ingredient (a.i.) L-1 florpyrauxifen-benzyl and exposed for 12, 24, or 48 hr under outdoor mesocosm conditions was reduced in biomass by 30%-75% at 8 weeks after treatment (WAT). An additional hydrilla trial at the same herbicide concentrations, but under longer exposures (24, 72, or 168 hr), resulted in 33-85% plant control. Under indoor conditions, hybrid watermilfoil dry weight decreased 98-100% with subsurface applications of florpyrauxifen-benzyl under CET scenarios of 3-12 microgram a.i. L at 3-24 hr exposure times in a growth chamber trial. Under shorter exposure periods (0.5-4 hr) in a follow-up trial, low doses (3-9 g a.i. L) achieved 50-100% control of hybrid watermilfoil. In the same trial, the nontarget species water stargrass and elodea proved relatively tolerant to the florpyrauxifen-benzyl at doses up to 6 microgram a.i. L-1 (4 hr exposure) and 9 microgram a.i. L-1 (1 hr exposure). These small-scale trials demonstrate florpyrauxifen-benzyls potential to selectively manage invasive species.