Detection and distribution of Leptopilina japonica Novkovic & Kimura, 2011 (Hymenoptera: Figitidae) in the Netherlands

Abstract Background : Leptopilina japonica Novković & Kimura (Hymenoptera: Figitidae), a parasitoid native to East Asia, has become an adventive species in Europe and North America, where it attacks the invasive spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), a major pest of soft fruits. Although L. japonica has been reported in several neighbouring European countries, its presence in the Netherlands had not been documented. Methods : In summer 2025, fruit samples were collected from 36 locations across seven Dutch provinces. Samples from non-agricultural habitats were incubated, and emerging insects were identified morphologically. Results : Parasitoids were recovered from 27 locations, with L. japonica accounting for >99% of the 1606 individuals recorded. The parasitoid was reared from multiple host plants of D. suzukii , including Rubus spp., Sambucus spp., and Prunus serrulata . D. suzukii was present at all sampled locations, and very few other drosophilid species were reared, confirming L. japonica ’s strong associations with the exotic fruit fly. The widespread detection of L. japonica at sites separated by up to 192 km indicates that viable populations are broadly established in the Netherlands. The host use and habitat preferences observed in this survey closely match those reported from both the native and other introduced ranges, suggesting that the species has similarly re-established its ecological associations in the Netherlands. Conclusions : These findings confirm that the ongoing spread of this parasitoid in Europe now includes the Netherlands and highlight its potential as a selective and effective biological control agent against D. suzukii .