Effects of an azadirachtin-based formulation on the non-target muscoid fly parasitoid Muscidifurax raptor (Hymenoptera: Pteromalidae)

Extracts from the Indian neem tree, Azadirachta indica (Meliaceae), have demonstrated high potential for the control of numerous insect pests. Azadirachtin [AZ], a tetranortriterpenoid compound, is considered the most important active principle contained in neem seed kernels. Although neem-based formulations are generally considered safe to beneficial insect species, adverse effects on hymenopteran parasitoids have been reported. The susceptibility of the muscoid fly pupal parasitoid Muscidifurax raptor to an azadirachtin-based insecticide was determined in laboratory bioassays. Parasitoid adults directly fed a diet containing the insecticide showed a slight reduction in their lifespan (25.1% and 15.7%, males and females, respectively) and reproduction rate (27.5%) at the highest concentration tested (20 μg [AZ]/ml). No significant effects were noticed at lower concentration. Interestingly, M. raptor males (LC50 = 43.0 μg [AZ]/ml) were more susceptible than females (LC50 = 94.7 μg [AZ]/ml). Immature parasitoids were able to develop and emerge successfully from house flies pre-treated at concentration levels that almost completely inhibited fly emergence (30 μg [AZ]/g). At this concentration level, longevity of emerging parasitoids was significantly reduced (20.6% and 17.6%, male and female, respectively), as was F1 progeny rate (35.9%), in comparison to the control.