Managing Cabomba caroliniana: prospects for integrating biological control and chemical control

Abstract

Cabomba caroliniana Gray, a submerged macrophyte, has become invasive in Australian waterways and is recognized as an invasive alien species globally. Despite the availability of various control methods such as herbicides, mechanical removal and biological control, their application can be significantly constrained by management objectives and site-specific conditions. For instance, in waterbodies used for recreational purposes where immediate removal of C. caroliniana is essential, biological control may not be suitable. Similarly, the use of herbicides in reservoirs that serve as drinking water sources is restricted due to contamination concerns. Recently, two novel approaches have been developed for managing C. caroliniana in Australia. The aquatic weevil, Hydrotimetes natans Kolbe, has been identified as a potential biological control agent. There is ongoing research to mass rear this weevil, in addition to ongoing releases of them in cabomba-infested ecosystems. Additionally, the contact herbicide flumioxazin, which inhibits protoporphyrinogen oxidase (PPO), has been evaluated for its efficacy and subsequently approved for treatment of C. caroliniana in Australia. To explore integrated control strategies, we conducted laboratory trials investigating the direct interaction between flumioxazin and H. natans. Our studies focused on assessing the herbicide's impact on the biology and behaviour of H. natans, including any changes in the expression of functional genes. The results indicate minimal to negligible detrimental effects of the herbicide on H. natans. In this talk, we highlight our results and discuss prospects for integrating biological control and chemical control to contribute to the catchment-level management of C. caroliniana.