First detection of the samurai wasp, Trissolcus japonicus (Ashmead) (Hymenoptera, Scelionidae), in Canada

Abstract

We report the first detection of Trissolcus japonicus, an exotic Asian egg parasitoid and the primary candidate for classical biological control of the invasive brown marmorated stink bug, Halyomorpha halys, in Canada. Twenty-eight Trissolcus japonicus emerged from an H. halys egg mass from a site heavily infested by H. halys in Chilliwack, British Columbia, in 2018. This egg mass was deployed and retrieved as part of ongoing sentinel egg mass surveys for natural enemies of H. halys from 2017–2018 in coastal and interior British Columbia (total of 1,496 egg clusters at 16 sites). The identification of T. japonicus was based on biology (high levels of successful emergence from H. halys eggs), morphology, and mitochondrial DNA sequences. Trissolcus japonicus was not detected at any other survey sites in 2017–2018; however, three species of indigenous egg parasitoids were found attending or emerging from H. halys egg masses at low levels (<4%) at several sites. The origin of the detected T. japonicus, the extent of its establishment in British Columbia, and its ultimate impact on H. halys populations remain to be determined. Nonetheless, the detection of this exotic biological control agent in Canada concurrently with regulatory review of its intentional importation and release is emblematic of the current uncertainty around regulatory control on the movement of biological control agents across borders.