Interactions between an ectoparasitoid and a nucleopolyhedrovirus when simultaneously attacking Spodoptera exigua (Lepidoptera: Noctuidae)

Insect pathogenic viruses and parasitoids represent distinct biological entities that exploit a shared host resource and have similar effects in suppressing host populations. This study explores the interactions between the ectoparasitoid Euplectrus plathypenae (Hymenoptera: Eulophidae) and the Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) in larvae of S.exigua (Lepidoptera: Noctuidae). Parasitoid progeny failed to complete development in hosts that had been infected prior to parasitism. However, infection of S.exigua fourth instars at 48 h post-parasitism had no significant effects on the survival of parasitoid progeny. Larval and pupal development times of E.plathypenae that survived on virus-infected S.exigua did not differ significantly from that of parasitoids on healthy hosts. Virus-induced mortality and the production of occlusion bodies were very similar in parasitized and non-parasitized S.exigua. The virus was genetically stable over three passages in parasitized and unparasitized hosts. These results suggest that applications of SeMNPV-based insecticides are unlikely to disrupt pest control exerted by the parasitoid E.plathypenae in biological pest control programs as long as virus applications are timed not to coincide with parasitoid releases.