Differential physiological effects of endo- and ecto-parasitoid venoms on the Asian citrus psyllid Diaphorina citri

Two different species of solitary parasitoid wasps have been used as biological control agents for the Asian citrus psyllid Diaphorina citri: the endoparasitoid Diaphorencyrtus aligarhensis and the ectoparasitoid Tamarixia radiata. Since little information was available on the role of the venom of these two parasitoid species in their reproductive success, we set up experiments to compare the effect of natural parasitism, natural envenomation (which was possible for T. radiata) and microinjections of D. aligarhensis and T. radiata venoms on the development and behavior of D. citri nymphs. We found that natural or artificial envenomation by T. radiata rapidly inhibited the crawling behavior of D. citri nymphs and subsequently induced a high nymph mortality rate, mimicking the natural effect of parasitization. In contrast, microinjection of D. aligarhensis venom did not affect nymphal crawling and had no clear effect on nymphal development apart from a slight delay in the days following injection, which may be consistent with the need to keep the host alive during parasitoid larval development. These results demonstrated the differential effects of venom from two types of parasitoid species sharing the same host, improving our understanding of the evolution of Hymenoptera parasitism and highlighting the use of parasitoid’s venom as a potential source of bioinsecticidal molecules.