Competitiveness of Irradiated Adults of the Indian Meal Moth1

Abstract

When unmated 24-h-old males of Plodia interpunctella (H�bner) were irradiated with 25 or 35 krad and confined with normal females, 80.2 and 96.5% of the eggs, respectively, did not hatch compared with 11.4% infertility of the control eggs. Increasing the dose to 50 or 75 krad induced complete sterility in the irradiated (I) males. Untreated (U) females mated with I males (25 krad) produced only 8.1 adults/100 eggs.When males treated with 25, 35 or 50 krad were confined with U males and U females (1:1:1 ratio), infertility of eggs was 41.2, 50.4, and 63.9, respectively. Thus, males treated with substerilizing doses (25 and 35 krad) competed favorably with U males, and males treated with the sterilizing dose (50 krad) were also fully competitive with U males, but 75 krad reduced ? competitiveness (30.8% egg infertility).Males and females both treated with a sterilizing dose (50 krad) and confined with U males and U females at a I ?:I ?:U ?:U ? ratio caused 67.85% infertility in the resulting eggs. When the ratio of sterile males and females was increased to 5:5:1:1, 10:10:1:1 or 15:15:1:1 (I ?:I ?:U ?:U ?), the percentage infertility reached 91.05, 97.65, and 99.75, respectively. The percentage of Actual infertility was less than the expected infertility for the ratios 1:1:1:1, 5:5:1:1, and 10:10:1:1, but it was exceeded with the highest ratio used (15:15:1:1). The competitiveness value for this flooding ratio was 1.00 (i.e., the sterile adults were fully competitive with the normal ones). These results indicated that irradiation with 50 krad, a sterilizing dose, did not decrease sexual competitiveness of adults. Also, the release of I males only or of I females together with I males could give good results in controlling a population of the Indian meal moth in an autocidal control program; and, therefore, separation of the sexes prior to release is probably unnecessary.