Invasive alien plants have serious economic and ecological impacts, for example, by displacing native plants and invertebrates, and their management is often costly and ineffective in the long term. Classical biological control (biocontrol) is advocated as an alternative to conventional invasive species management that has the potential for long term, self-perpetuating and effective control, especially in more sensitive environments such as protected areas or riparian habitats.
A Natural England stakeholder workshop in 2022, which aimed to prioritise species for biological control, identified Carpobrotus edulis as a priority species given its impacts upon sensitive coastal habitats. This mat-forming succulent is a transformer species which is challenging to control across its coastal range. A biocontrol feasibility assessment carried out by CABI in 2021-22 flagged several natural enemies of C. edulis with potential to impact upon the plant. Of those species, the scale insect Pulvinariella mesembryanthemi has been recorded outdoors in the UK on the Isles of Scilly, and on the mainland in Cornwall.
The current study aimed to assess C. edulis populations across key regions of the plant’s invasive range in the UK; provide information on the natural enemy pressure on C. edulis by scale insects in GB and associated scale parasitoids and to undertake a further assessment of natural enemies from South Africa for classical biocontrol.
A test plant list for assessment of candidate biocontrol agents for C. edulis in the UK (with consideration of European flora) is also provided, developed in consultation with an expert botanist experienced in biocontrol research.