Current status of Drosophila suzukii classical biological control in Italy

For over a decade, the invasive pest Drosophila suzukii (Matsumura) has threatened the soft-skinned fruit production worldwide, causing increased management costs and yield losses. Current integrated pest management (IPM) exploits different control tools but relies mainly on insecticides. The local natural enemy community mostly consists of generalist species, mainly parasitoids attacking the puparia of the fruit fly. These antagonists resulted unable to control the pest efficiently, regardless the adoption of conservative or augmentative approaches. By contrast, in the native area of D. suzukii, sympatric larval parasitoids have co-evolved with the pest and provide a stable control of its population. Foreign explorations and quarantine risk assessment studies for classical biological control programs have identified different species of parasitoids characterized by a variable level of specificity. The Japanese G1 lineage of the larval endoparasitoid Ganaspis brasiliensis (Ihering) has proved to be much more selective and efficient than other larval parasitoids, including Leptopilina japonica Novković & Kimura recently reported in Europe. In this context, a voluntary partnership of Italian researchers imported a colony of the G1 lineage of G. brasiliensis into Italian quarantine facilities and proposed its release in Italian fields. A three-year working program has been set up in several locations of nine Italian regions/provinces. Field releases of laboratory-reared parasitoids have been planned. Pre- and post-release samplings of fresh and fallen fruits around the release points will be undertaken to assess the impact of the exotic G. brasiliensis on D. suzukii and its potential interactions with other non-target insects in the field. The possible establishment of this efficient and specific biological control agent would promote a long-lasting control of this invasive species less dependent on the use of chemicals, reducing the negative effects associated with them.