Evippe Moth Biocontrol Agent Application: Update

5 April 2024

Conservation

The Ascension Island Government’s Conservation and Fisheries Directorate (AIGCFD), with support from the Darwin Plus-funded project, DPLUS134: Repelling the invader: turning the tide on Ascension’s Mexican thorn, submitted an application to the Governor to approve the release of the Evippe moth as a biocontrol agent.

This initiative is part of a strategic approach to manage the invasive Mexican thorn, which poses a threat to the island's biodiversity such as our green turtle and seabird nesting habitats, strongholds for the Ascension Island spurge, and endemic cricket population. The submission followed consultations with the public and Island Council in 2023, followed by extensive testing and risk assessment conducted by the Centre for Agriculture and Bioscience International (CABI) in the UK and AIGCFD to ensure the moth would specifically target Mexican thorn, and have no significant direct negative impacts on native, endemic, or introduced plant or animal species.

The Evippe moth has been successfully used for this purpose in Australia and South Africa, demonstrating a significant reduction in the growth and spread of the Mexican thorn. As a result, Mexican thorn plants in Australia where Evippe has become established rarely produce much foliage. Repeated defoliation has contributed to the very low seed production and growth rates observed since 2000. If this can be repeated on Ascension, long-term control of Mexican thorn may be possible. This would reduce the need for costly and time-consuming cutting and spraying efforts to protect Ascension’s native or endemic plants and animals, as well as the island’s infrastructure.

The testing phase included rigorous assessments of an extensive range of plants that have been tested for susceptibility to the Evippe moth during biological control programmes conducted in Australia and South Africa. In addition, plant species endemic or native to Ascension Island, plus a selection of species, including lettuce cultivated horticulturally or for ornamental purposes on Ascension Island have been tested as part of the DPLUS134 project to ensure negligible impact on other plant species. This step was a part of AIG’s focus on sustainable environmental management and the protection of Ascension’s unique biodiversity. The successful results paved the way for AIGCFD to seek the Governor’s approval to proceed with the release. The Governor gave his approval on 22 February 2024.

The next stage of the project is to transport the cultured moths from the UK to Ascension to a culture facility already established in One Boat. Moths will be released at suitable sites around Donkey Plain and a monitoring program will begin to measure the impact of the moth along transects from the release sites. A Monitoring and Evaluation Plan has been drafted and will be published on the AIG website when finalised.

Due to the high level of public interest in this subject, the Government Response to Consultation document has been published and the full Evippe Risk Assessment is also being published. Public Notices and social media posts will be distributed regularly. For further details, please contact the Mexican thorn Control Project Officer, Chrisna Visser on 66403 or email chrisna.visser@ascension.gov.ac