Sterilization of the Mediterranean Fruit Fly with Gamma Radiation: Effect on Male Competitiveness and Change in Fertility of Females Alternately Mated with Irradiated and Untreated Males1

Competitiveness of males of Ceratitis capitata (Wiedemann), irradiated in the late pupal stage with 5 to 11-krad gamma radiation was evaluated from the egg hatch resulting when irradiated males were confined in various ratios with untreated pairs of insects. Competitiveness decreased with increased close. This factor counteracted the increased degree of sterility induced by increased dose, so doses of 5–11 krad led to similar reductions in egg hatch. With increased replication it was possible to distinguish between the degree of control given by 5-, 7-, or 9-krad-treated males and 9 krad gave the poorest control. Although 7 krad allowed a slightly higher level of fertility in males than did 9 krad (5% vs. 1–2%, respectively) the data indicate that use of 7 krad rather than 9 krad should be seriously considered in eradication, and especially suppression, programs for this species. Evidence was obtained that the presence of sterile females neither augmented nor detracted from the degree of control given by irradiated males. The egg hatch of females confined with irradiated males after an initial mating with untreated males was lowered, but to a smaller extent, as the dose given to males was increased from 5 to 11 krad. With the reverse mating sequence the increase in egg hatch was greater as the irradiation dose was increased.