The story

Across Europe, invasive plants are overrunning delicate ecosystems, including waterbodies. Here, they are particularly difficult to control. Conventional management methods, including chemical herbicides and mechanical removal, are costly. Moreover, they can harm the wider environment and even worsen the spread of invasive plants. Science can provide nature-based, sustainable solutions – a much-needed alternative approach to chemical and manual control. 

CABI scientists have led the development of biocontrol to tackle two of the most damaging aquatic weeds: floating pennywort (Hydrocotyle ranunculoides) and Australian swamp stonecrop (Crassula helmsii). Biocontrol reduces reliance on chemicals. It also lowers costs and restores healthier waterbodies for people and biodiversity. 

After years of research and rigorous testing to ensure only target species are affected, CABI scientists have confirmed two specialist natural enemies, the weevil Listronotus elongatus and the mite Aculus crassulae as effective and safe biocontrol agents for Hydrocotyle Crassula respectively. Reared in controlled facilities and released at carefully selected sites, these tiny organisms affect only their target species, reducing their growth and ability to spread. 

UK field trials have shown the biocontrol agents capable of successfully establishing and dispersing. Moreover, they significantly suppress the growth of invasive Hydrocotyle and Crassula, enabling native vegetation to recover. In 2025, building on this success, CABI supported the first-ever biocontrol releases of these agents in the Netherlands. Following regulatory approval, the organisms were reared in the UK and released in partnership with Dutch research institutes and water authorities. 

Led by our UK centre, newly relocated to Imperial College’s Silwood Park, this cross-border collaboration harnesses shared scientific expertise. By working in partnership, coordinated results can deliver sustainable invasive species management.