Controlling Cabomba caroliniana with different flumioxazin application strategies

Abstract

Cabomba caroliniana, a fully submerged aquatic plant originating from South America, has become highly invasive outside of its native range. It impacts native aquatic ecosystems, reduces biodiversity, affects public safety and economy. Flumioxazin is an efficient herbicide for managing cabomba while being environmentally safe. However, a single application is often insufficient to completely control cabomba. Consequently, follow-up applications become necessary to completely remove cabomba. We carried out a mesocosm study, replicated in winter and summer, to find the optimum dose and frequency of flumioxazin applications for effectively controlling cabomba. Single, or multiple low doses of flumioxazin spaced over time, were injected directly into outdoor mesocosms with a high density of cabomba. In the winter trial, the control efficacy of four application strategies (50 + 50 ppb, 50 + 50 + 50 ppb, 100 + 100 ppb and 200 ppb) on cabomba biomass reduction ranged from 86.3% to 95.5%. Meanwhile, in the summer trial, the biomass reduction of cabomba caused by the four strategies ranged from 98.1% to 100%. However, the differences between the four strategies were not significant both in summer and in winter. In conclusion, all four application strategies of flumioxazin have high efficacies on cabomba biomass reduction. A single high application (200 ppb) of flumioxazin can achieve a rapid biomass reduction of cabomba. The strategy of split applications of low dose can be used when there are other flumioxazin-sensitive native aquatic plants, which can achieve the same efficacy of flumioxazin with much less non-target damage. Further research will now investigate the efficacy of flumioxazin application strategies in the field.