Overflooding Ratios in the Sterile Insect Technique: Toward Sustainable Management of Bagrada hilaris

The Sterile Insect Technique (SIT) is an eco-friendly control method that may prove effective against Bagrada hilaris, a pest native to India, Southeast Asia, and Middle and central Africa and reported as invasive in the southwestern USA, Hawaii, Mexico, South America, and two Mediterranean islands. This insect causes significant crop damage due to its intense feeding behavior and is currently managed almost exclusively with synthetic insecticides. In this context, SIT offers a promising alternative for controlling B. hilaris populations, provided that sufficient numbers of sterile males are continuously released. Based on this premise, we conducted a preliminary laboratory study to evaluate the overflooding ratio (OFR)--the proportion of non-irradiated to irradiated males required to suppress the populations fertility. We tested various OFRs (1:1, 1:2, 1:5, and 1:10), monitoring both the number of eggs laid and hatching rates. Our results show a significant decrease in fertility as the percentage of irradiated males increases. Among the ratios examined, 1:5 emerged as the most advantageous in terms of both reducing fertility and ease of application. Although further validation under field conditions is needed, our findings suggest that SIT could effectively contribute to an integrated management strategy for B. hilaris, reducing the reliance on chemical pesticides and supporting a more sustainable approach.