I think I can remember that I saw a presentation during my studies about the relevance of generalists in hindering insect pest mass gradations. The think explanation was that generalists are not dependent of the population dynamic of the pest insects. So there is a base abundance of the generalists compared to specialized parasitoids, which are not able to end the mass gradation, because their population dynamic is delayed in relation to the host population dynamic. Would be nice to have reference for that issue. Thanks for answering.