Consequences of Interspeci ® c Competition on the Virulence and Genetic Composition of a Nucleopolyhedrovirus in Spodoptera frugiperda Larvae Parasitized by

Nucleopolyhedroviruse s (Baculoviridae) are virulent insect pathogens that generally show a high degree of host speciWcity and have recognized potential as biologica l insecticides. Whenever viruses are applied for pest control, a proportion of the infected insects will also be parasitized by hymenopteran or dipteran parasitoids and interspeciWc competition for host resources will occur; the severity of such competition is likely to be modulated to a large degree by the virulence of each type of parasite. We examined the impact of parasitism by the solitary egg-larval endoparasitoi d Chelonus insularis (Hymenoptera: Braconidae) on the speed of kill of nucleopolyhedrovirus-infected Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae and the pattern of host growth and virus production in infected and/or parasitized hosts. We also examined the eVect of parasitism on the virulence, infectivity and genetic composition of serially passaged virus. Both parasitism and viral infection resulted in a marked reduction in host growth. When third instar larvae were dually parasitized and virus-infected, the growth rate was even more severely aVected compared to parasitized larvae. There was a signiWcant increase in virus production in larvae infected at later instars. InterspeciWc competition resulted in a substantial decrease in pathogen production in parasitized larvae infected at the fourt