Advancing Heterospecific Sterile Insect Technique Against Drosophila suzukii: selection of the optimal irradiation dose for D. melanogaster males

The spotted-wing drosophila (Drosophila suzukii), a highly invasive agricultural pest, poses significant challenges to fruit production worldwide. Traditional chemical control methods are costly and raise concerns about resistance and environmental sustainability. The Heterospecific Sterile Insect Technique (h-SIT) has emerged as a promising alternative, using sterile heterospecific males (Drosophila melanogaster) to suppress D. suzukii populations through reproductive interference. However, optimizing irradiation doses is critical to balancing male sterility, maintaining biological quality and mating performances. This study aimed to determine the optimal irradiation dose for D. melanogaster males by assessing their sterility, longevity, and courtship behavior following exposure to gamma-ray doses ranging from 80 to 180 Gy. Results showed a significant reduction in fertility across all irradiation doses, with near-complete sterility at 180 Gy. However, longevity decreased with increasing doses, with males irradiated at 160-180 Gy showing a lifespan reduction of up to 50 days compared to controls. Behavioral trials revealed that irradiated D. melanogaster males retained their courtship ability toward D. suzukii females, although males exposed to 160 Gy exhibited reduced courtship activity. These findings highlight that, among the tested doses, 80 Gy emerged as the most effective, preserving male longevity and mating performance while significantly reducing fertility. While 180 Gy achieved the highest sterility, the potential lifespan and courtship behavior trade-offs warrant further evaluation. Future studies should evaluate field performance to refine the balance between sterility, longevity, and mating performances for effective D. suzukii population suppression.