The sterile insect technique (SIT) is used in area-wide pest management programs for establishing low pest prevalence and/or areas free of fruit flies (Diptera: Tephritidae). The aim of this technique is to induce high levels of sterility in the wild population, for this the released insects must have a high sexual competitiveness and field dispersal. However, radiation decreases these biological attributes that do not allow it to compete successfully with wild insects. In this study the sexual competitiveness, field survival and dispersal of Anastrepha obliqua (Macquart; Diptera: Tephritidae) irradiated at 0, 40, 50, 60, 70, and 80 Gy were evaluated in laboratory. A dose of 60 Gy produced 98% sterility, whereas doses of 70 and 80 Gy produced 99% sterility. Sexual competitiveness was assessed in field cages, comparing males irradiated at 0, 50, 60, 70, and 80 Gy against wild males for mating with wild fertile females. Males irradiated at 50 and 60 Gy achieved more matings than those irradiated at 70 and 80 Gy. Wild males were more competitive than mass-reared males, even when these were not irradiated (0 Gy). There was no effect of irradiation on mating latency, yet wild males showed significantly shorter mating latency than mass-reared males. Female remating did not differ among those that mated with wild males and those that mated with males irradiated with different doses. The relative sterility index (RSI) increased from 0.25 at 80 Gy to 0.37 at 60 Gy. The Fried competitiveness index was 0.69 for males irradiated at 70 Gy and 0.57 for those irradiated at 80 Gy, which indicates that a 10 Gy reduction in the irradiation dose produces greater induction of sterility in the wild population. There were no significant differences in field survival and dispersal between flies irradiated at 70 or 80 Gy. Reducing the irradiation dose to 60 or 70 Gy could improve the performance of sterile males and the effectiveness of the SIT. Our results also distinguish between the effects of irradiation and mass-rearing on the performance of sterile males.

Anastrepha obliqua (Macquart) (Diptera: Tephritidae), commonly known as the West Indies fruit fly, is a pest species of mango, plum (both Anacardiaceae), and other commercial crops in various countries in the Neotropics, including Mexico, Central and South America, and the Caribbean islands. Currently, the sterile insect technique (SIT) is used to control this pest. Here, the sexual competitiveness of mass-reared sterile A. obliqua males was evaluated against wild males in field cages. In the first experiment, fertile mass-reared males had similar sexual performance as fertile wild males reared on mango and tropical plum. In the second experiment, sterile mass-reared males had better sexual performance than sterile wild males recovered from mango and tropical plum. In the third experiment, fertile wild males recovered from mango had better sexual performance than sterile mass-reared males. The relative sterility index (RSI) was 0.32, indicating low acceptance of sterile males by wild females. The induced sterility index estimated by Fried's test produced a coefficient of 0.4, indicating that irradiation affected the sexual performance of the mass-reared males, which had reduced sexual performance compared to wild males. We discuss our results in the context of mass-rearing and sterilization as part of the SIT programs used to control A. obliqua.