Post-release evaluation of non-target effects of Torymus sinensis, the biological control agent of Dryocosmus kuriphilus in Italy

A post-release study was performed to assess the impact of Torymus sinensis (Hymenoptera: Torymidae), the biological control agent of Dryocosmus kuriphilus (Hymenoptera: Cynipidae), on native cynipid gall inducers in Italy. In total, 14,512 non-target galls were collected, corresponding to seven genera: Andricus , Aphelonyx , Biorhiza , Cynips , Diplolepis , Neuroterus , and Synophrus , and 8708 chalcid parasitoids were recorded. The Torymidae family accounted for about 30%, and Bootanomyia (= Megastigmus ) dorsalis , Torymus affinis and T. flavipes were the most represented species. A total of 116 T. sinensis emerged from 15 different oak galls, mainly Andricus curvator and A. inflator . In controlled conditions, oviposition was recorded on A. cydoniae , A . grossulariae and A. lucidus , while no mating with native congeneric species occurred. This paper confirms the realised host-range expansion by T. sinensis . Even if it were extremely difficult to evaluate its magnitude, the impact appears minimal, and an occasional feeding with no changes in the distribution or abundance of non-target hosts is expected.