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.

The use of light spectrum blocking films to reduce populations of Drosophila suzukii Matsumura in fruit crops.

Spotted wing drosophila, Drosophila suzukii, is a serious invasive pest impacting the production of multiple fruit crops, including soft and stone fruits such as strawberries, raspberries and cherries. Effective control is challenging and reliant on integrated pest management which includes the use of an ever decreasing number of approved insecticides. New means to reduce the impact of this pest that can be integrated into control strategies are urgently required. In many production regions, including the UK, soft fruit are typically grown inside tunnels clad with polyethylene based materials. These can be modified to filter specific wavebands of light. We investigated whether targeted spectral modifications to cladding materials that disrupt insect vision could reduce the incidence of D. suzukii. We present a novel approach that starts from a neuroscientific investigation of insect sensory systems and ends with infield testing of new cladding materials inspired by the biological data. We show D. suzukii are predominantly sensitive to wavelengths below 405 nm (ultraviolet) and above 565 nm (orange & red) and that targeted blocking of lower wavebands (up to 430 nm) using light restricting materials reduces pest populations up to 73% in field trials.

Insecticide Control of Drosophila suzukii in Commercial Sweet Cherry Crops under Cladding.

Drosophila suzukii Matsumura is a damaging invasive pest of sweet cherry. Using a series of laboratory leaf contact assays, semi-field, and orchard spray programs we aimed to determine the impact of insecticide programs on D. suzukii adult mortality and oviposition in cladding-protected sweet cherry crops. Tests included assessing adult D. suzukii mortality after contact with leaves sprayed either one or two weeks previously and emergence of adults from fruits. Spinosad, lambda-cyhalothrin, acetamiprid, lime, pyrethrin, deltamethrin, and cyantraniliprole all reduced fruit damage up to day 7 after application. Of these active ingredients, only spinosad, lambda-cyhalothrin, and cyantraniliprole gave satisfactory control up to 14 days. There was no significant difference in D. suzukii mortality when exposed to leaves treated either one or two weeks previously with an application of either spinosad, cyantraniliprole, or lambda-cyhalothrin; however, mortality was significantly higher than D. suzukii in contact with untreated leaves. In eight commercial orchards, fortnightly spray applications including spinosad, cyantraniliprole, and lambda-cyhalothrin gave effective control of D. suzukii until harvest with very few damaged fruits. These experiments demonstrate that currently approved plant protection products, applied to sweet cherry under protection, give at least two weeks protection from D. suzukii.