First records of adventive populations of the parasitoids Ganaspis brasiliensis and Leptopilina japonica in the United States

Abstract

We report the first known incidence of two parasitoid species of the invasive pest, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), in the United States (US). The discovery of Ganaspis brasiliensis (Ihering) (Hymenoptera: Figitidae) and Leptopilina japonica (Novkovic & Kimura) (Hymenoptera: Figitidae) in northwestern Washington State (US) was made shortly after their discovery in nearby southwestern British Columbia (Canada), indicating that contiguous populations of these species are established in both countries. The first specimen of L. japonica from Washington was collected in the fall of 2020, when it was found in a rice wine/orange juice trap deployed to survey for Vespa mandarinia Smith (Hymenoptera: Vespidae). Subsequent examination of trap contents from the 2020 2021 seasons indicated the presence of both L. japonica and G. brasiliensis. In September of 2021, live collections of both G. brasiliensis and L. japonica were made, reared from D. suzukii-infested Himalayan blackberry in Whatcom County, WA. Adult parasitoid identifications were based on morphology and COI DNA barcodes. All sequenced specimens to date from Washington and British Columbia belong to the G1 group of G. brasiliensis, the only group approved for release as a classical biological control agent in the US. This study provides an example of how even small changes in the geographic range of a natural enemy, now extending across an international border, may have significant consequences for the future of a biological control program.