Conservation Evidence strives to be as useful to conservationists as possible. Please take our survey to help the team improve our resource.

Providing evidence to improve practice

Action: Crassula helmsii: Decontamination to prevent further spread Control of Freshwater Invasive Species

Key messages

Read our guidance on Key messages before continuing


Supporting evidence from individual studies


A replicated, controlled container experiment in 2013-1014 in the UK (Anderson et al. 2015) found that exposure to hot water led to higher mortality of C. helmsii fragments compared to drying treatment or a control. Submerging C. helmsii in hot water caused 90% mortality 1 h after treatment, and all plants were dead after 1 day. Hot water followed by drying did not result in additional mortality (80% mortality after 1 h). Drying treatment only led to partial mortality (20% after 8 days and 50% after 16 days), and all fragments in the control group survived for 16 days. Two hundred and forty 60 mm plant fragments were placed in mesh bags and submerged in 14 °C water for 1 h to simulate an angling trip. Hot water samples were then submerged in 45°C water for 15 min. Samples in the drying treatment were put on plastic trays in a room with circulating air. Control samples were placed in unsealed plastic bags to hinder drying. Mortality was assessed after 1 h and 1, 2, 4, 8 and 16 days using a FluorPen.


Referenced papers

Please cite as:

Aldridge, D., Ockendon, N., Rocha, R., Smith, R.K. & Sutherland, W.J. (2019) Some aspects of control of freshwater invasive species. Pages 569-602 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.