The Pereskia stem-wilter, Catorhintha schaffneri (Coreidae), a new biological control agent for Pereskia aculeata (Cactaceae). Eighteen months since release, where are we now?

The Pereskia stem-wilter, Catorhintha schaffneri (Coreidae), a new biological control agent for Pereskia aculeata (Cactaceae). Eighteen months since release, where are we now?
Pippa MUSKETT, Iain D. Paterson
Biological Control Research Group, Department of Zoology & Entomology, Rhodes University, Grahamstown

Catorhintha schaffneri Brailovsky & Garcia (Coreidae), a biological control agent for the invasive alien plant, Pereskia aculeata Miller (Cactaceae), was first released in South Africa in 2014. The first releases resulted in variable success with establishment at some sites but populations quickly dying out at others. This study aims to determine which factors may impact establishment success so that release efforts can be optimised. Climatic conditions were investigated in an experiment where 30 adults were released at sixteen sites in different climatic zones. Establishment through winter was only recorded at two sites, one in Amanzimtoti and another in Port Alfred. Low establishment rates were likely due to the low release effort at all sites. The fact that the population survived winter in a relatively cold site, such as Port Alfred, indicates that the thermal tolerance of the agent is likely to be suitable for it to survive winter at most sites, given that P. aculeata is most abundant in the warm sub-tropical parts of the country. The importance of release effort was investigated in another experiment where low release effort (30 adults), medium (60 adults), high (120 adults) and multiple releases (30 adults released every week for four consecutive weeks), were tested. Establishment was successful at all the multiple release sites, only 33 % of sites with releases of 60 and 120, and 16 % of sites where 30 adults were released. By conducting multiple small releases at each site the establishment success rate for C. schaffneri will be increased.