Granulovirus-infected larvae of Pseudaletia separata (Lepidoptera: Noctuidae) produce factor(s) toxic to an endoparasitoid, Cotesia kariyai (Hymenoptera: Braconidae)

Abstract

Interactions between the Hawaiian strain of a granulovirus of Pseudaletia unipuncta (PuGVH) and a gregarious braconid endoparasitoid, Cotesia kariyai, in Pseudaletia separata larvae were examined. The results showed that infection of larvae with PuGVH was deleterious to the development and survival of C. kariyai. No parasitoid larvae emerged from PuGVH-infected hosts when the second and third instars were infected with PuGVH and then parasitized at the fourth stadium. Further, no parasitoid larvae also emerged from PuGVH-infected hosts when the fourth instars of P. separata were simultaneously parasitized and infected with PuGVH. Virion-free plasma from PuGVH-infected P. separata larvae was toxic to the parasitoid larvae even up to a dilution level of 256 when it was injected intrahemocoelically into parasitized host larvae. Toxicity of the virion-free plasma was maintained for at least 4 d after its injection into host larvae. Addition of the virion-free plasma was also toxic to the in vitro-cultured parasitoid larvae, even up to a dilution level of 625. The cuticles of dead parasitoid larvae were separated from the somatic tissues.