Interactions between parasitoids of Drosophila suzukii
Drosophila suzukii (Diptera: Drosophilidae – EPPO A2 List) is a pest originating from East Asia that differs from other vinegar flies in its ability to oviposit in healthy and ripening fruits. Ganaspis kimorum (Hymenoptera: Figitidae), formerly G. brasiliensis G1, is a larval parasitoid classical biological control agent that has recently been introduced into the EPPO region and the USA as a classical biological control agent against D. suzukii. The performance of G. kimorum may be affected by other parasitoids. For example, Pachycrepoideus vindemiae (Hymenoptera: Pteromalidae) and Trichopria drosophilae (Hymenoptera: Diapriidae – Appendix 1 PM 6/3) are two cosmopolitan generalist pupal parasitoids that attack D. suzukii and both have been extensively evaluated as biological control agents for conservation and augmentative control strategies against D. suzukii. A study consisting of no-choice and choice tests was conducted to determine the parasitoids preference to attack unparasitized or parasitised puparia. No-choice tests demonstrated that both pupal parasitoids could parasitise puparia previously parasitised by G. kimorum but only P. vindemiae successfully developed from multi-parasitised puparia. In choice tests, both pupal parasitoids preferred unparasitized over parasitised puparia, no differences in the progeny sex-ratio were observed. Integrating these cosmopolitan parasitoids for the control of D. suzukii should be assessed at an early stage of a biocontrol programme as they have the potential to reduce the effectiveness of the classical biological control agent. Even with a preference for unparasitized hosts, both pupal parasitoids demonstrated the potential to undermine the effectiveness of classical biological control with G. kimorum.
Sources
Lisi F, Rogers DV, Henry EE, Hogg BN, Biondi A, Wang X, Daane KM (2025) Potential interactions of larval and pupal drosophila parasitoids and their implications for biological control of Drosophila suzukii. Biological Control 204, 105756. https://doi.org/10.1016/j.biocontrol.2025.105756