This research project will investigate the influence of mass releases of natural enemies on local natural enemies via resource competition in egg parasitoids. The project will study whether replacement is dependent on the abundance and species composition of non-target hosts naturally occurring in the proximity of the release sites.
The inundative release of large numbers of beneficial insects could possibly not only effect populations of the targeted pest insect, but might also effect populations of other insects in that area (non-target effects). While effects on non-target hosts (e.g. local butterfly populations) are usually considered, effects on local parasitic wasp populations (intraguild-competition) have rarely been studied.
A thorough risk-assessment strategy and subsequent monitoring of the released organisms are key components of modern and environmentally safe biological control procedures. Therefore, in this project, we will monitor genetic variation in natural populations of Trichogramma species, tiny parasitoids of butterfly eggs, in cabbage fields across Germany. Monitoring will take place before and after Trichogramma brassicae has been released for biocontrol purpose. Laboratory studies on fitness effects of non-target hosts are included. In addition, genetic markers for this wasp will be developed together with ESR1 at Wageningen University. These will allow us to study wasp persistence at the release site and thus, to optimise commercially used Trichogramma lines.