Drosophila suzukii (Matsumura) a new pest of grape in Veneto Region (north-east Italy)

Abstract: The vinegar fly Drosophila suzukii (Matsumura) (Diptera Drosophilidae), spotted wing drosophila (SWD), is a highly polyphagous invasive pest endemic to Southeast Asia, which has recently invaded Italian regions. Serious economic losses were reported on soft fruits; furthermore damage was expected in late-maturing crops, such as grapevines, which are not protected by insecticides. For this reason the presence, ecology and harmfulness of D. suzukii was monitored in a grape growing area where late-ripening red grape varieties are cultivated (Verona district, Veneto Region). SWD adults were captured in all investigated vineyards, the larger populations were observed in higher hill sites compared with foothills and plain. The adult presence in the vineyards is influenced by the existence of other SWD host plants both cultivated or wild, on the areas surrounding vineyards, especially cherries: infested fruits left on the trees after harvest constituted a source of re-infestation. The larvae infestations occurred only in high hill sites on grapes ripening for the late vintage. At harvest, more than 60% of bunches were infested, with 1-2 infested berries per bunch on the autochthonous varieties Rondinella and Corvina, while on the international varieties Merlot and Cabernet sauvignon less than 30% of bunches were infested, with 0.5 infested berries per bunch. Implications for D. suzukii control on grape are discussed.