The invasive ACGW Dryocosmus kuriphilus (Hymenoptera: Cynipidae) in Spain: native parasitoid recruitment and association with oak gall inducers in Catalonia

The Asian chestnut gall wasp (ACGW), Dryocosmus kuriphilus (Hymenoptera: Cynipidae), is an invasive pest that affects chestnut trees. The first record of this pest in Spain was in 2012, in Catalonia, and it is now distributed in virtually every chestnut growing area in the country. In this study, we present an overview of parasitoid recruitment by ACGW in Catalonia over a 4-year period (2013–2016) comparing parasitoid communities attacking galls on oak and chestnut trees at the same sites. A total of 22 species of native parasitoids that normally attack oak cynipids emerged from ACGW galls, together with the non-native Torymus sinensis. The most abundant species were Bootanomyia dorsalis, Torymus flavipes, Ormyrus pomaceus and Eupelmus urozonus. The study also found that 20 of the 22 native parasitoids in ACGW galls were also reared from galls of 13 species of oak gall inducer (12 Cynipidae, 1 Cecidomyiidae).