Seasonal and regional presence of hymenopteran parasitoids of Drosophila in Switzerland and their ability to parasitize the invasive Drosophila suzukii

Abstract

Since its introduction into Europe the invasive Drosophila suzukii has established and spread widely, thereby entering habitats populated by native Drosophila species and their natural enemies. The highly prolific D. suzukii will likely interact with these species as a competitor, host or prey. To investigate potential interactions of D. suzukii with parasitoids, a field survey was conducted across several fruit-growing regions in Switzerland in two consecutive years. Eight species of hymenopteran parasitoids were collected using D. melanogaster as sentinel hosts in field-traps. Parasitoid capture was much higher in 2015 than in 2014 and varied among regions, time of the growing season, and habitat type. Laboratory no-choice assays with the field-collected species demonstrated that the larval parasitoids Asobara tabida, Leptopilina boulardi, and L. heterotoma could not use D. suzukii for reproduction, although the latter two reduced the number of emerging D. suzukii. In contrast, the pupal parasitoids Pachycrepoideus vindemmiae, Trichopria drosophilae, Vrestovia fidenas and Spalangia erythromera all developed with D. suzukii as hosts. Regional differences between strains were generally not evident, with the exception of two T. drosophilae strains that differed in parasitization rate. Thus, native parasitoids may interact with D. suzukii and should be regarded when implementing pest control measures.

Development of Asian parasitoids in larvae Of Drosophila Suzukii feeding on blueberry and artificial diet

“…These results suggest that L. heterotoma's virulence is not strong enough to resist the immune reaction of D. suzukii. This was also observed in other studies (Chabert et al, 2012;Kacsoh & Schlenke, 2012;Knoll et al, 2017;Poyet et al, 2013;Rossi Stacconi et al, 2017).…”

“…These results suggest that L. heterotoma's virulence is not strong enough to resist the immune reaction of D. suzukii. This was also observed in other studies (Chabert et al, 2012;Kacsoh & Schlenke, 2012;Knoll et al, 2017;Poyet et al, 2013;Rossi Stacconi et al, 2017).However, a single female succeeded to complete its development in this study, and higher rates of successful development were observed when testing various geographic strains of the parasitoid (P. Girod A. japonica and L. japonica that attacked and developed in larvae in both substrates, Ganaspis sp. parasitized many more larvae in blueberries compared to artificial diet.…”

“…Finally, L. heterotoma females may be less adapted to pierce the skin of a fresh blueberry, which requires a stronger penetration force (Burrack et al, 2013) and is also more time-consuming than searching for hosts in decaying fruits or artificial diet. However, a small number of larvae in blueberries were (Chabert et al, 2012;Kacsoh & Schlenke, 2012;Knoll et al, 2017;Poyet et al, 2013;Rossi Stacconi et al, 2017).…”

“…and may provide an area-wide control of fly populations (Carton, Bouletreau, Lenteren, & Alphen, 1986;Fleury, Gibert, Ris, & Allemand, 2009). Two generalist pupal parasitoids, Trichopria drosophilae Perkins (Hymenoptera, Diapriidae) and Pachycrepoideus vindemmiae (Rondani) (Hymenoptera, Pteromalidae), are found attacking D. suzukii worldwide and are being studied as potential biological agents for inundative control in crops; however, their impact on natural populations is low (Gabarra, Riudavets, Rodríguez, Pujade-Villar, & Arnó, 2015;Knoll, Ellenbroek, Romeis, & Collatz, 2017;Rossi Stacconi et al, 2015, 2017. In the invaded regions, larval parasitoids such as Leptopilina heterotoma (Thompson) (Hymenoptera, Figitidae), Leptopilina boulardi Barbotin, Carton & Keiner-Pillault (Hymenoptera, Figitidae) and Asobara tabida (Nees) (Hymenoptera, Braconidae), which are important natural enemies of local Drosophila spp., are rarely able to develop successfully in D. suzukii larvae, partly because of the strong host immune response of the fly larvae (Chabert, Allemand, Poyet, Eslin, & Gibert, 2012;Gabarra et al, 2015;Poyet et al, 2013;Rossi Stacconi et al, 2015).…”

Plant neighbour identity and invasive pathogen infection affect associational resistance to an invasive gall wasp

“…oak galls being more suitable hosts. Some parasitoid species could have indeed avoided ACGW galls and concentrated on native hosts as infecting a new introduced host may incur a fitness cost for native parasitoids (Jones et al 2015;Knoll et al 2017). …”