Seasonal flight activity of Drosophila suzukii and first data on its population genetics and parasitoid occurrence on Mount Etna (Italy)

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is a serious invasive crop pest native to Asia and currently widespread in many parts of the globe. However, little information is available on its seasonal abundance in southern Italian fruit crops, including Mount Etna (Sicily, Italy). Here, we aimed at investigating i) the pest seasonal flight activity, ii) its population genetics, and iii) the potential occurrence of associated parasitoids. To this end, traps were deployed in five locations of strawberry and cherry districts of East and North-West sides of the Mount Etna for one year. In addition, host-parasitoid interactions with wasp species sampled by sentinel fruit trapping were investigated under laboratory conditions. The East locations were warmer than the North-West ones, and flies were captured all year except in August. In the North-West locations no flies were caught during the winter. Fly captures peaked in late spring and autumn in all locations. Sequencing of a portion of the mithocondrial cytochrome oxidase I (COI) from individuals of D. suzukii indicated a population genetic identity suggesting a single source of invasion. The field trapping revealed the occurrence of one larval parasitoid, Leptopilina boulardi (Barbotin, Carton and Kelner-Pillault) (Hymenoptera: Figitidae), and two pupal parasitoids, Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae) and Trichopria drosophilae Perkins (Hymenoptera: Diapriidae). Nevertheless, only the pupal parasitoids were able to successfully develop on D. suzukii in laboratory bioassays. While obtained results indicate that climatic conditions strongly affect the local f ly population and represent the bases for developing sustainable D. suzukii management programs, native parasitoid impact on pest population dynamic should be further investigated in this region-specific context.