Cold storage of Ganaspis kimorum immature stages for optimized classical biological control of Drosophila suzukii

Authors: LISI, FABRIZIO - University Of Catania; BIONDI, ANTONIO - University Of Catania; Hogg, Brian; ROSSI-STACCONI, MARCO VALERIO - Fondazione Edmund Mach; Wang, Xingeng; DAANE, KENT - University Of California Berkeley

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2024
Publication Date: 12/13/2024
Citation: Lisi, F., Biondi, A., Hogg, B.N., Rossi-Stacconi, M., Wang, X., Daane, K.M. 2024. Cold storage of Ganaspis kimorum immature stages for optimized classical biological control of Drosophila suzukii. Journal of Economic Entomology. 2024,1-9. https://doi.org/10.1093/jee/toae286.
DOI: https://doi.org/10.1093/jee/toae286

Interpretive Summary: Spotted wing drosophila (SWD) is an invasive fruit fly that has become a major pest of soft-skinned fruits (raspberries, blueberries, cherries, etc.) in the Americas and Europe. A parasitic wasp from Asia is being released in many countries to help control SWD, and mass rearing and storage techniques must be developed to optimize production of the wasp. We investigated a method for storing immature stages of the wasp (larvae, pupae, nearly developed adults) at two temperatures (10 or 15 °C) for 2, 4, 6 or 8 weeks. Immature wasps developed and emerged as adults at some of these temperatures, indicating that these temperatures were not suitable for storage. We then focused on those temperatures that prevented parasitoid emergence, and the impacts of temperatures on wasp development time (DT) and emergence rate (ER) were then measured. We also examined effects on longevity and parasitism ability of adult wasps that emerged. Results showed that only wasp larvae and pupae were suitable for storage at cold temperatures. Cold exposure significantly delayed the DT of larvae and pupae, while the ER was reduced only for larvae at 10 °C for 6 weeks. The longevity of emerging male and female wasps was significantly reduced when stored at cold temperature as larvae, while no effects were reported for parasitism by emerged females. These findings provide new insights into the cold sensitivity of this parasitic wasp and offer valuable options for mass rearing and releasing the wasp.

Technical Abstract: Programs to mass rear and release Ganaspis kimorum Buffington (Hymenoptera: Figitidae) are ongoing in many countries threatened by its host, the invasive fruit fly Drosophila suzukii (Matsumura) (Diptera: Drosophilidae). To optimize parasitoid production and to synchronize field releases with the pest outbreaks, we investigated a cold storage protocol by exposing three G. kimorum immature stages (larvae, pupae, pharate adults) to two storage temperatures (10 or 15 °C) for 2, 4, 6 or 8 weeks. Immature parasitoids could complete their development and emerge during some of these temperatures and, therefore, we identified and further studied those treatments that prevented parasitoid emergence before the end of each cold exposure, or the cold storage suitability (CSS). The impact of cold storage treatments on G. kimorum emergence time (ET), total development time (TDT) and emergence rate (ER) was then evaluated for treatments with CSS > 60%. We also assessed fitness costs in terms of longevity and parasitism rates of emerging parasitoids. Results showed that only G. kimorum larvae and pupae were suitable for cold storage under this methodology. Cold exposure significantly delayed the ET and TDT of larvae and pupae, while the ER was significantly reduced only for larvae at 10 °C for 6 weeks. The longevity of emerging male and female parasitoids was significantly reduced when cold stored as larvae, while no effects were reported for parasitism rate by emerged females. These findings provide new insights into G. kimorum cold sensitivity and offer valuable options to better schedule mass rearing and wasp releases.