Competitiveness of Gamma-Sterilized Males of the Mediterranean Fruit Fly1

Male Ceratitis capitala (Weidemann) given gamma doses of 1–17 krad 2 days before adult eclosion were confined with untreated males and females in ratios of 5:1:1, 9:1:1, and 19:1:1. With the first 2 ratios, the egg hatch of treatments using 5-, 7-, 9-, or 11-krad-treated males was not significantly different despite an increase in male sterility from approximately 89 to more than 99%. In the 19:1:1 ratio experiment, the 7-krad treatment gave the lowest egg hatch, and it was significantly lower than that for the 11-krad treatment. Males irradiated with greater than 3 krad were less competitive than untreated males based on a comparison of observed and expected egg hatch. When the competitiveness of the irradiated males was quantified, it was clear that as the dose increased male competitiveness decreased.