VOCs-Mediated Location of Olive Fly Larvae by the Braconid ParasitoidPsyttalia concolor: A Multivariate Comparison among VOC Bouquets from Three Olive Cultivars

Abstract

Herbivorous activity induces plant indirect defenses, as the emission of herbivorous-induced plant volatiles (HIPVs), which could be used by parasitoids for host location.Psyttalia concoloris a larval pupal endoparasitoid, attacking a number of tephritid flies includingB. oleae.In this research, we investigated the olfactory cues routing host location behavior ofP. concolortowardsB. oleaelarvae infesting three different olive cultivars. VOCs from infested and healthy fruits were identified using GC-MS analyses. In two-choice behavioral assays,P. concolorfemales preferred infested olive cues, which also evoked ovipositional probing by female wasps. GC-MS analysis showed qualitative and quantitative differences among volatiles emitted by infested and healthy olives. Volatile emissions were peculiar for each cultivar analyzed. Two putative HIPVs were detected in infested fruits, regardless of the cultivar, the monoterpene (E)-β-ocimene, and the sesquiterpene (E-E)-α-farnesene. Our study adds basic knowledge to the behavioral ecology ofP. concolor. From an applied point of view, the field application of the above-mentioned VOCs may help to enhance effectiveness of biological control programs and parasitoid mass-rearing techniques.