It has been about one year since the first releases of Selitrichodes neseri, biological control agent for Leptocybe invasa. This minute parasitic wasp was first released in the Zululand region in July 2012 after about two years of intensive research at the quarantine facilities of the FABI Biocontrol Centre, University of Pretoria, which led to approval from the Department of Agriculture, Forestry and Fisheries (DAFF) for its release. Now, one year later, S. neseri has been released at over 300 sites across the most highly infested areas in the KwaZulu-Natal, Mpumulanga and Limpopo provinces. This translates to the release of over 6 000 female wasps. It is not known how long it will take before there is noticeable impact on the populations of L. invasa, but results from post-release studies are very positive. Selitrichodes neseri has been recaptured from all the release sites included in the post-release study, and parasitism levels of up to 9% have been obtained at some sites just five months after the original release. Expectations are that, in time, parasitism rates will increase to over 70%, as obtained in contained release sites in Pretoria.
Efforts are underway to investigate the establishment of S. neseri at a larger number of release sites and so determine whether further releases are required in those areas. FABI PhD student Kwabena Baffoe is also investigating factors that could possibly influence parasitism of S. neseri, including the interaction between biological control and host resistance strategies.
Thank you to Ryan Nadel (ICFR) for providing the attached map showing the release sites as of July 2013.
by Brett Hurley