Olfactory cues for host selection in Ganaspis brasiliensis G1
Ganaspis brasiliensis G1 (Hymenoptera: Figitidae) is a classical biological control agent of Drosophila suzukii (Diptera: Drosophilidae – EPPO A2 List). It has been released in Northern Italy and studies have shown it can survive in the areas where released (EPPO RS 2023/023). The G1 lineage only parasitises host larvae that develop in the ripening fresh fruit, on the plant, and not larvae that develop in decaying fruit. To assess the chemical cues that are utilised by G. brasiliensis females to locate (1) the host fruit, (2) suitable larvae and (3) to tell the difference between fresh and decaying fruit, experiments were carried out using a choice olfactometer and blueberry bioassays. The olfactory bioassays presented a choice to G. brasiliensis G1 females and included - D. suzukii infested fruit, healthy fruit, and pure air. Females showed a time dependant attraction to the cues based on the stage of the fruit (healthy versus decaying) where females were attracted to infested fruit during the early stages of infestation. Females were repelled by fruit degraded by larval feeding. The attractiveness of G. brasiliensis G1 females towards fruits infested by young larvae was associated with the detection of VOCs released by the infested blueberries, and the hosts cuticular hydrocarbons. G. brasiliensis G1 females were repelled by a fermentation compound produced by microorganisms likely to be carried inside the fruit by the flies.
Sources
Giorgini M, Rossi-Stacconi MV, Pace R, Tortorici F, Cascone P, Formisano G, Spiezia G, Fellin L, Carlin S, Tavella L, Anfora G, Guerrieri E (2024) Foraging behavior of Ganaspis brasiliensis in response to temporal dynamics of volatile release by the fruit–Drosophila suzukii complex. Biological Control 195, 105562. https://doi.org/10.1016/j.biocontrol.2024.105562