Induced sterility by gamma radiation in Callosobruchus maculatus (Col.: Bruchidae) and sterile insect release ratio to a normal population

Effects of gamma radiation doses on Callosobruchus maculatus (F.) were studied. In this study different doses including 0, 20, 35, 50, 60 and 70 Gy were used in the pupal stage and emerged adults were separated before mating and crossed in treatments including: normal male  normal female, normal male  irradiated female, irradiated male  normal female and irradiated male  irradiated female. Comparing means (Duncan,s test, 0.05) showed that in 20 Gy, all treatments had significant difference, except normal male  normal female and normal male  irradiated female. In 35 Gy, all treatments had significant difference. The most sterility was observed in irradiated male  irradiated female and it was not significantly different with irradiated male  normal female. In 50 Gy, treatments which contained irradiated males or irradiated females had significant difference with treatments containing normal males and females. In 60 and 70 Gy, hatchability percentage in the next generation, both for sterile males and sterile females, reduced population significantly. Therefore, 60 to 70 Gy induce sterility in this insect. Sterile insect release to a normal population was studied in three cases including: sterile male, sterile female and sterile male and female releases. Results indicated that sterile female release had no effect on reducing population in the next generation. Sterile male release and sterile male and female release had identical effects. As a regard to the fact that separating males and females is difficult and time consuming, therefore, it seems that sterile male and female release in the ratio of 10:10:1:1 (irradiated male  irradiated female  normal male  normal female) cause the best result in population reduction in the next generation.