Control of emergent invasive aquatic plants with the herbicide florpyrauxifen-benzyl (ProcellaCOR FX) in Australia

Abstract

Invasive alien aquatic plants (IAAPs) cause major ecological and socio-economic impacts, yet management in Australia is constrained by the limited number of herbicides registered for aquatic use. Florpyrauxifen-benzyl (ProcellaCOR FX, 300 g a.i. L-1), registered in Australia in 2025, was evaluated in outdoor mesocosms using foliar application at 15 and 30 g a.i. ha−1 and liquid injection at 25 and 50 ppb. The control efficacy of florpyrauxifen-benzyl was tested on four emergent invasive macrophytes: Rotala rotundifolia (Buch.-Ham. ex Roxb.) Koehne (rotala), Myriophyllum aquaticum (Vell.) Verdc. (parrot’s feather), Heteranthera reniformis Ruiz & Pav. (kidney-leaved mudplantain) and Bacopa lanigera (Cham. & Schltdl.) Wettst. (hairy water hyssop, bacopa). All species responded rapidly with a steady decline in plant health over time. M. aquaticum and H. reniformis were the most sensitive, with complete biomass control across all treatments. B. lanigera and R. rotundifolia were also highly susceptible, although control efficacy was more variable and slightly reduced for the lower foliar and injection rates. Biomass reductions at 42 d after treatment was 99-100% cross all species with liquid injection, thus providing the most consistent control. These results indicate that florpyrauxifen-benzyl will provide an excellent tool for managing the tested emergent species. The most appropriate application method and application rate will depend on specific site conditions, target species and economic considerations.