Chiara Elvira Mainardi

Bagrada hilaris (known as painted bug) is a pest native to India, Southeast Asia, and middle and central Africa and was reported as invasive in the southwestern USA, Hawaii, Mexico, South America, and two Mediterranean islands. The feeding activity results in extensive damage to economically important Brassicaceae crops. Among sustainable alternatives to synthetic pesticides, the Sterile Insect Technique (SIT) is considered a promising strategy because it relies on the release of competitive sterile males that can reduce the pest reproduction. In this study, the efficacy of different doses of gamma irradiation (60, 80, and 100 Gy) was evaluated to identify the treatment that would ensure high sterility without compromising the competitiveness of the treated males. Observational tests showed that the doses of 60 Gy and 80 Gy showed no difference in mating times compared to non-irradiated males, in contrast to 100 Gy. Thus, 80 Gy was identified as the most promising dose. For further investigation, tests were conducted under choice and no-choice conditions at 80 Gy for three days. The results showed that irradiated males had a comprehensive higher mating rate than non-irradiated males, and under choice conditions, they were often preferred by females, confirming that SIT has potential as an environment-friendly method for controlling B. 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 population’s 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.