Combined effects of biological control agents on host populations of Drosophila suzukii
Drosophila suzukii (Diptera: Drosophilidae – EPPO A2 List) is a frugivorous fly native to East Asia. It has spread to many regions worldwide, including other parts of Asia, the Americas, Africa and the EPPO region. Hymenoptera parasitoids are important biological control agents that can parasitise D. suzukii larvae and pupae though there is little research that has been conducted in combining both for the management of D. suzukii. This was evaluated using the larval parasitoid Leptopilina japonica (Hymenoptera: Figitidae) and 2 pupal parasitoids, Trichopria drosophilae (Hymenoptera: Diapriidae) and Pachycrepoideus vindemmiae (Hymenoptera: Pteromalidae). Experiments were conducted using blueberries as the host to raise D. suzukii where individual berries were infested with 5, 10, 15, 20, 25 or 30 eggs. Following the development of the larvae to the second instar, or to the pupae, a single mated female parasitoid (either L. japonica, T. drosophilae, or P. vindemmiae) was introduced. Experiments were also conducted where all three parasitoids were released, over time into a cage containing developing D. suzukii larvae. For both experiments, measurements were taken including the number of offspring produced, host stinging without oviposition-induced mortality, and total host mortality caused by the parasitoids. Individually, all three parasitoids showed increased efficiency with increased host density though L. japonica showed higher mortality at high densities (≥20 hosts) compared to the pupal parasitoids. Population suppression experiments found that the combined release of L. japonica and T. drosophilae achieved the optimal control, reducing the number of D. suzukii adults after 45 days. Using biological control agents in combination can have increased impact on the host population, however other studies have shown that combined effects of biological control agents can have reduced effectiveness (EPPO RS 2025/132).
Sources
Bin SY, You Q, Bai QR, Zhang Y, Sun JW, Zang LS (2026) Individual and combined effects of larval and pupal parasitoids in the control of Drosophila suzukii (Diptera: Drosophilidae): implications for biological control. Journal of Economic Entomology. 119(2), 831–839. https://doi.org/10.1093/jee/toaf340