Abstract: 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 μg 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 μg a.i. L⁻¹ 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 μg a.i. L⁻¹) 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 μg a.i. L⁻¹ (4 hr exposure) and 9 μg a.i. L⁻¹ (1 hr exposure). These small-scale trials demonstrate florpyrauxifen-benzyl’s potential to selectively manage invasive species.