Recruitment of native parasitoids to a new invasive host: first results of Dryocosmus kuriphilus parasitoid assemblage in Croatia

Research on recruitment of native parasitoids on the recently introduced invasive species Dryocosmus kuriphilus has been carried out on four sites in 2011 and 2012 in Croatia. In total 15 species of native parasitoids were reared which belong to 5 of 6 chalcid families attacking native oak cynipid gallwasps (Eupelmidae - 2, Eurytomidae - 4, Ormyridae - 1, Pteromalidae - 4 and Torymidae - 4 species). This research has shown that the time lag between introduction of new host and recruitment of native parasitoids is short. Sex ratios for the most abundant parasitoid species appeared to be female-biased and the parasitoid emergence rate for all sites was relatively low. Torymus flavipes was recorded from D. kuriphilus at all sites and in both years and was the most abundant species exploiting the new host. Among other species, especially Torymus flavipes and Megastigmus dorsalis, which have been reared from D. kuriphilus galls, could provide a good possibility for biological control but further research is needed