Historical context ‒ the USA biocontrol program for Cape ivy
Cape ivy has been the target of a biocontrol program in the USA, with comprehensive natural enemy surveys performed over several years in the native range of South Africa. Initial risk assessments performed by the USDA on several potential insect agents identified the shoot tip-galling fly Parafreutreta regalis and the leaf and stem-boring moth Digitivalva delaireae as the most promising candidate agents for Cape ivy.
Parafreutreta regalis is a gall-forming member of the fruit fly family. In its native range in South Africa, it has only been observed on Cape ivy. It was introduced to California as a biocontrol agent for Cape ivy in 2017 by the USDA. Studies conducted prior to this release confirmed that P. regalis is highly host-specific to Cape ivy (within the USA context). Pre-release efficacy studies showed that even low levels of P. regalis attack significantly reduced the height and biomass of Cape ivy. Vines with galls were visibly stunted compared to ungalled stems, which were longer and had more nodes and larger leaves than galled stems. See additional information here:
Digitivalva delaireae is a leaf and stem-mining moth. Under laboratory conditions, it has been shown to significantly reduce Cape ivy stem growth and invasion potential. Results from host-specificity tests have demonstrated that it is sufficiently host specific to Cape ivy for introduction into the USA. An application to release the moth into western USA is currently being assessed by regulators. Further information about the release program can be found here:
The key activities of the current research are to:
- Nominate Cape ivy as a target for biological control.
- Review previous research conducted as part of the USA biological control program for this weed.
- Undertake risk assessment of at least one agent for the Australian context.
- If deemed safe, preparing applications for their release into Australia.