Yorkshire Water is stepping up the fight against one of the UK’s most invasive non-native aquatic weeds by working with scientists from the Centre for Agriculture and Bioscience International (CABI) to release an army of mites to suppress the weeds. Approval has been given for the release of a novel biological control agent – the mite, Aculus crassulae – at Gouthwaite reservoir in Nidderdale to assess its ability to suppress the Australian swamp stonecrop (Crassula helmsii) weed. The trial follows carefully controlled laboratory testing to ensure the safe, controlled release of the mite in the UK.

The weed was introduced to the UK in the early 1900s as a decorative garden pond plant, but is no longer considered attractive due to its impact on native biodiversity. The plant can form dense mats in still and slow moving water bodies, dominating sensitive aquatic environments and threatening native plants and invertebrates. It can also exacerbate flood risk as well as clogging pipes and intakes. It is hoped that the release of the mites, as part of research commissioned by the Department for the Environment Food and Rural Affairs (Defra), will help to reduce the spread of Crassula helmsii in water bodies and areas of high conservation status. Click here to read more