Preliminary evidence of Drosophila suzukii parasitism in Southeast England.

Controlling the invasive fruit pest, Drosophila suzukii, relies on a range of complimentary pest management approaches. However, increasing external costs (e.g., labour, exclusion mesh and fuel), are limiting the ability to control the pest via non-chemical means. Extant UK parasitoids could be exploited for the suppression of D. suzukii populations, but there is currently a lack of knowledge of the UK species utilising D. suzukii as a host or their lifecycle requirements. Between 2017 and 2020, we identified parasitoids developing in D. suzukii, in Southeast England.Sentinel traps, containing laboratory reared D. suzukii larvae/pupae in fruit, were deployed within the vicinity of commercial crops and semi-natural areas. Six generalist parasitoid species were recovered from D. suzukii sentinel traps. These included two species of larval parasitoids (Leptopilina heterotoma Thomson (Hymenoptera: Figitidae) and Asobara tabida (Nees) (Hymenoptera: Braconidae) and four pupal parasitoids (Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae), Spalangia erythromera (Forster) (Hymenoptera: Pteromalidae), Trichopria modesta (Ratzeburg, 1848) and T. prema Nixon (both Hymenoptera: Diapriidae)).The performance of the first four species as D. suzukii parasitoids was further tested in the laboratory and then in the field to assess rates of parasitism. Pachycrepoideus vindemiae was the most abundant species recovered from field collections and had in increasing rate of population rate in the laboratory. Other species were not successful at parasitising D. suzukii. In the field, adult D. suzukii emergence from sentinel traps was reduced by ~ 21% where parasitoids could access D. suzukii larvae and pupae.Parasitoids of D. suzukii are understudied in the UK, and this research indicates where future efforts could be made in understanding the interaction between host and parasitoid and the opportunities to exploit extant parasitoids for the control of D. suzukii. We also evaluate the prospects for classical and augmented control and discuss how they may fit with current regional integrated pest management options.