In this paper, we report the use of a new spatially implicit host-parasitoid model to compare different biological control strategies. We demonstrate how this approach could be used as a decision tool for crop protection by testing various strategies for the inoculative release of parasitoids to target a pest in a greenhouse. The results show that a single curative release of parasitoids is more effective than a single preventative release: that is, the best strategy is to release as many parasitoids as possible once the pest has invaded the crop if the parasitoid exhibits a type II functional response, or to do so a few days later for a type III functional response. We also confirm that multiple releases are more effective than single releases, and that the initial distribution of the pests and the functional response of the parasitoids are decisive factors for the effectiveness of the biological control (parasitoids with a type II functional response being more effective than those with a type III response).