Food-deprived host-feeding parasitoids kill more pest insects

Abstract

Some parasitoids not only parasitize their hosts but also destructively feed on them which could result in host mortality. We hypothesized that host-feeding parasitoids that are food-deprived before being released for biological control would destructively feed on more hosts, and an optimal duration of food deprivation of parasitoids would enhance host feeding without negatively affecting parasitism. We investigated the effects of food-deprivation durations (0, 3, 6, 10, 24 h and 20% honey solution offered), before being released, on the host mortality and parasitism by a destructive host-feeding parasitoid of whitefly nymphs, Encarsia sophia (Girault & Dodd) (Hymenoptera: Aphelinidae). In another experiment, we compared host feeding, parasitization and longevity throughout the lifespan between food-deprived and non-food-deprived parasitoids. Using fourth-instar Bemisia tabaci B biotype as the host, the responses of E. sophia differed significantly with the durations of food deprivation before they were exposed to their hosts. E. sophia adults food-deprived for 6 h killed more hosts through feeding than those that were food-deprived for 0, 3, 10 and 24 h or those that were fed with honey solution. Moreover, parasitoids that were food-deprived for 6 h parasitized more hosts than those held for other durations of food deprivation. Similar results on host-feeding were found when third-instar whitefly nymphs were used. We confirmed that E. sophia food-deprived for 6 h not only killed more whiteflies through host feeding, but also lived significantly longer and parasitized more hosts than the non-food-deprived ones throughout their lifespan. Our results could be extended to improve the effectiveness of augmentative biological control of pests through improved host feeding and parasitizing capacity by starving the parasitoids for a certain period of time before they will be used.