Berry skin resistance explains oviposition preferences of Drosophila suzukii at the level of grape cultivars and single berries

Drosophila suzukii (Matsumura) is an invasive species, which is able to attack intact ripening fruit and has become a serious pest in the Americas and Europe. However, susceptibility toward D. suzukii varies strongly within and between grapevine cultivars. The aim of our study was to differentiate between berry parameters influencing oviposition of D. suzukii in grapevine with two complementary approaches. We investigated the influence of berry skin resistance, total soluble solids (a sugar related parameter), acidity and volatile acidity on grape susceptibility; in the first approach at the cultivar level in a field survey, and in the second approach at the single berry level in a laboratory choice experiment. Both approaches revealed that berry skin resistance explained oviposition decidedly better than chemical composition of the berries did: Soft skinned cultivars and berries received significantly more eggs than hard skinned cultivars and berries. These findings suggest a major role of berry skin resistance in the susceptibility of grapevine toward D. suzukii. The cultivar approach identified the cultivars Dornfelder, Trollinger (=Vernatsch, Schiava), Portugieser, Roter Elbling and Cabernet Dorsa to be susceptible, whereas Dakapo, Lemberger (=Blauer Limberger) and Riesling showed no oviposition by D. suzukii. Nevertheless, parameters like previous damage, climate, environment and plant protection may have an additional impact.