Improved mating performance of male Anastrepha ludens (Diptera: Tephritidae) irradiated at low doses for release in sterile insect technique programmes

In this study, laboratory and field cage experiments were conducted to assess the performance of sterile mass-reared Mexican fruit fly Anastrepha ludens (Loew) irradiated at various doses. In small laboratory cages, the radiation dose was found to have no effect on adult emergence, flying adults or survival at 25 days. In field cages, non-irradiated males and males irradiated at 20 and 40 Gy were found to exhibit greater mating propensity than males irradiated at 60 and 80 Gy. In large field cages in competition with wild males, cohorts of flies (male and female) irradiated at the low dose of 40 Gy and wild non-irradiated flies mated randomly, while flies irradiated at the high standard dose of 80 Gy mated assortatively. Irrespective of the radiation dose, laboratory flies courted and attempted copulation significantly earlier in the day than wild flies. In large field cages, cohorts of flies irradiated at low doses, e. g. 40 Gy, tended to induce greater sterility into a cohort of wild flies than those irradiated at 80 Gy, but the difference was not significant. Our results suggest that lowering the radiation dose currently applied to mass-reared flies in the Mexican fruit fly eradication campaign would substantially improve male mating performance. This could result in greater sterility induction without posing a risk in areas where target pest populations naturally prevail and are under suppression during the early stages of eradication programmes.