Characterization of native parasitoid community associated with the invasive pest Dryocosmus kuriphilus (Hymenoptera: Cynipidae) in Cantabria (northern Spain)

Abstract

A survey of the native parasitoid community was conducted to characterize its possible use as biological control for Asian Chestnut Gall Wasp (ACGW) at two sampling sites in northern Spain. To this end, 500 ACGW galls were collected over five sampling dates between May and July 2017; 250 of them were dissected to estimate the parasitism rates and the remaining 250 galls were placed in emerging rearing boxes to collect adult parasitoids. Seven native parasitoid species belonging to six families (i.e. Eupelmidae, Eurytomidae, Ormyridae, Megastigmidae, Pteromalidae and Torymidae) were identified by morphological traits. All sampled species are considered as native parasitoids of gallers-oaks (Quercus spp.). The most abundant species were Sycophila variegata (Curtis), Torymus auratus (Müller) and Sycophila biguttata (Swederus), representing 70% of the identified parasitoids. In addition, the presence of these native parasitoids was associated with high parasitism rates, especially at the site that was surrounded by oak trees. Our findings highlight the important contribution of native parasitoids to pest regulation throughout the period of ACGW gall development.