Epsilon Archive for Student Projects

Abstract

Baculoviruses manipulate insect larval behaviour by inducing increased activity and by
enhancing the movement to the top of the host plant. The Spodoptera littoralis
nucleopolyhedrovirus (SpliNPV) may have a large impact on larval populations and is
currently used as a control method. Dispersal of NPVs is fairly limited since foliage or
infected larvae need to be ingested for transmission. S. littoralis is cannibalistic under high
population densities or low food availability conditions. We hypothesized that healthy larvae
recognize and are attracted to virus-infected cadavers. Dual choice experiments in petri dish
arenas, involving infected and uninfected larval cadaver suspensions revealed no significant
differences in neonate larval attraction. In contrast, fourth instar larvae fed significantly more
on infected larval cadavers than on cadavers of uninfected larvae. Although mortality of
larvae that fed on infected cadavers was increased, high mortality in both groups suggests
vertical transmission of the virus in this species. Our results show that that virus-killed
cadavers increase attraction and feeding by healthy larvae. Consumption of conspecific
cadavers increases viral dissemination. Our results suggest that larvae killed by NPV infection
emit chemical cues, which make them more attractive to conspecific larvae, thereby
promoting in viral transmission.