Host plants of the herbivorous insect Mythimna separata (Lepidoptera: Noctuidae) affect its susceptibility to parasitism by the larval parasitoid Cotesia kariyai (Hymenoptera: Braconidae)

Previous studies have shown that the food plant species consumed by herbivorous insects affect their parasitism by parasitoid wasps or flies, but this phenomenon has only been observed in a limited number of systems. Here, we investigate how feeding on different plant species affects the survival of the rice armyworm Mythimna separata (Walker) (Lepidoptera: Noctuidae) and its successful parasitism by the larval endoparasitoid Cotesia kariyai (Watanabe) (Hymenoptera: Braconidae). Survival rate and pupal weight of unparasitised M. separata fed with daikon Raphanus sativus L. var. longipinnatus was lower than with maize Zea mays L. In addition, caterpillars fed with daikon were less susceptible to parasitism by C. kariyai than those fed with maize, and parasitised M. separata larvae fed with daikon had higher survival rates than those fed with maize. These results indicate that while daikon is not an optimal food for unparasitised caterpillars, it may protect the larvae from death by C. kariyai parasitism.