This project explores complex interactions between cruciferous plants, one of their most important herbivores, the diamondback moth, Plutella xylostella, and its major parasitoid, Diadegma insulare. The diamondback moth is a major, world-wide pest of crucifer crops. The work examines the role of variable sex ratios in parasitoids and their herbivorous hosts in population regulation and dynamics of 3-trophic level systems. It concentrates on direct and indirect effects of plants on interactions between herbivbores and parasitoids and tests the hypothesis that interactions between sex-ratio variation and plant preferences of the moths and wasps provide a mechanism for density-dependent regulation of herbivore populations over several generations. The project will provide detailed estimated of the effects of plants on both herbivore and comprehensive dynamic models. The work is relevant to questions of stability of parasitoid-host dynamics and to biological control in an economically important system.
