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 is mostly composed by generalist species, such as parasitoids attacking fruit fly puparia, unable to control the pest efficiently, in both conservative and augmentative strategies. 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 programmes have identified different species of parasitoids showing variable levels 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 coordinated by the Italian National Plant Protection service 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 will go along with pre- and post-release sampling of fresh and fallen fruit around the release area, in order to assess the G. brasiliensis impact on D. suzukii and the potential interactions with other non-target insects. The potential establishment of such an efficient biological control agent would promote the permanent sustainable control of this invasive species thus making IPM less dependent on the use of chemicals, reducing the issues associated with it.