Affect of food provisioning on survival and reproductive success of the olive fruit fly parasitoid, Psyttalia lounsburyi, in the field

Conservation biological control offers approaches that can be integrated into classical biological control programs to enhance pest suppression. Food subsidies, such as nectar and honeydew, can increase a parasitoid’s fecundity either by extension of the reproductive lifespan, increasing the rate of egg maturation, or both. The olive fruit fly, Bactrocera oleae, is a major pest of olives in California, where a classical biological control program is currently underway using an exotic parasitoid, Psyttalia lounsburyi. We conducted a field study where female–male pairs of P. lounsburyi wasps were caged with B. oleae-infested olives, and provisioned either with or without food. Our study showed that adult feeding is crucial to P. lounsburyi survival and fecundity under field-cage conditions. Food provision increased P. lounsburyi survival and several components of the wasp’s reproductive success; nevertheless, parasitism rates and offspring production were relatively low. This was probably due, at least in part, to location of host larvae in enemy-free space ‘beyond the reach’ of the wasp’s ovipositor. Sex ratio of offspring was male-biased, perhaps due to inbreeding in the laboratory colony from which P. lounsburyi was sourced. Female wasps carried ca. 25–35 eggs at their time of death, suggesting that they were time limited rather than egg limited. Integration of conservation biological control (e.g., food provisioning) and classical biological control (release of an exotic natural enemy) have promise to suppress olive fruit fly populations. Evaluation of the effect of food provisioning on P. lounsburyi reproductive success under open field conditions is warranted.