Beneficials such as predators and parasitoids, which are used for biological pest control, can also harm non-target organisms. To be able to assess the environmental risks before the release of such beneficials, it is important to know the physiological and behavioural factors constituting the host- or prey spectrum.
Although a high level of specificity is commonly regarded as one of the advantages of biological pest control, the full potential host or prey spectrum for a given beneficial is seldom known. For this reason, the risk of non-target species being attacked by a new beneficial must be assessed prior to the latter's release.
We investigate which physiological factors and types of behaviour in hosts and parasitoids increase the likelihood of host switching. The host switching of parasitoids which might possibly parasitise the invasive Drosophila suzukii in addition to native fruitfly species serves as a model system for our investigations. The native parasitoid species Bracon variator, which has a particularly wide host spectrum (caterpillars, weevil larvae) and may perform a seasonal host switch, serves as a second model system.