Efficacy of flumioxazin effervescent tablet on controlling Cabomba caroliniana : a field study

Abstract

Cabomba caroliniana A. Gray (cabomba) is an invasive aquatic plant that presents significant ecological challenges to freshwater systems in Australia. Flumioxazin effervescent tablet (Clipper), registered since 2021 in Australia, is an effective herbicide for its management. To evaluate the herbicide’s field performance and optimise its practical application, a field experiment was conducted in Kevin Kaeser Lake, Morayfield, Queensland, testing cabomba suppression in relation to water depth and other environmental factors (e.g. light intensity) at the point of application. Ninety-two days after treatment, each herbicide tablet produced a visible clearing in the cabomba canopy averaging 16.6 ± 15.7 m², corresponding to a treated water volume of 27.3 ± 34.1 m³ and a 62.2% reduction in local plant biovolume. The maximum recorded visible impact reached 25.0 ± 24.8 m² in surface area and 34.9 ± 46.3 m³ in water volume, with a 63.0% reduction in biovolume. Notably, the extent of control was not significantly influenced by water depth at the release point. However, phytoplankton (algae) presence at the application sites was observed to delay herbicide activity by affecting underwater light availability, though it did not compromise the ultimate control efficacy. These findings support the use of flumioxazin effervescent tablets as an effective strategy for managing localised cabomba infestations, particularly in waterbodies characterised by diverse aquatic plant communities, where cabomba populations are patchily distributed across various discrete locations.