Melon Flies: Dosage-Response and Sexual Competitiveness After Treatment with Gamma Irradiation in a Nitrogen Atmosphere12

Abstract

Doses of 18–19 had of gamma-irradiation were needed to produce a level of sterility of 99.5% or higher in ♂ Dacus cucurbitae Coquillett treated in nitrogen as pupae 2 days before eclosion or as 2- or 5-day-old adults. The same level of sterility was obtained with 6–8 krad when pupae or 2-day-old adults were irradiated in air. Males irradiated in nitrogen either as pupae or as 2-day-old adults were fully competitive with normal ♂, but ♂ treated in nitrogen as 5-day-old adults and ♂ irradiated in air as 2-day-old adults or as pupae were only 40–60% as competitive as normal males. Recovery of fertility with time occurred in ♂ treated in nitrogen as 2-day-old adults, although not in ♂ treated in nitrogen in the late pupal stage. However, mortality in ♂ treated in nitrogen in the pupal stage at 6 wk was about twice that of the former groups.