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

Citation

P.K. Abram, E.J. Talamas, S. Acheampong, P.G. Mason, and T.D. Gariepy (2019). First detection of the samurai wasp, Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) in Canada. Journal of Hymenoptera Research (in press).

Plain language summary

The brown marmorated stink bug (Halyomorpha halys), native to Asia, is a serious invasive alien pest that has caused extensive economic damage and increases in insecticide use in wide range of crops, and it is also a nuisance pest in human dwellings. This pest has recently established in Canada, posing a serious threat to crop production. Its principal natural enemy in Asia, the samurai wasp (Trissolcus japonicus), has been under consideration for importation and release for biological control the brown marmorated stink bug in the USA, Canada, and Europe for several years. However, since 2014, the samurai wasp has been found to have established on its own (adventively) in several areas of the USA and Europe. In this article, we report a detection of the samurai wasp at a site infested by brown marmorated stink bug in Chilliwack, British Columbia, representing the first record of the samurai wasp in Canada. The origin of the detected population, the extent of its establishment in British Columbia, and its ultimate impact on brown marmorated stink bug populations remain to be determined. However, given the relative proximity (<400km) of the closest known established populations in Washington State, it is plausible that this detection is indicative of a range expansion of adventive samurai wasp populations and that they are in the early phases of establishment in British Columbia.

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 at the same time as its intentional importation and release is under regulatory review is emblematic of the current uncertainty around regulatory control on the movement of biological control agents across borders.