[en] Moths of plutella maculipennis curtis and crocidolimia binotalis zell radiosterilized with 30 Krad and 40 Krad of gamma radiation respectively were released into a laboratory-cage of 90 cm x 60 cm x 60 cm, a field-cage of 2 m x 2 m x 2 m and an experimental plot of 10 m x 15 m to study their effect on the reduction of F1-population. The release of 450 irradiated moths in the laboratory-cage containing 50 unirradiated moths can reduce the F1-population of plutella maculipennis and crocidolomia binotalis by 61.1% and 65.3% respectively. While in the field-cage the F1-population of plutella maculipennis and crocidolomia binotalis decreased by 55.6% and 50.55% respectively. The release of about 4.500 irradiated crocidolomia binotalis into an experimental plot containing 500 normal moths can reduce the F1-population by 41.02% in the dry season and 50.55% in the rainy season. The release of about 5.000 irradiated moths of plutella maculipennis into an experimental plot containing about 350 moths of natural population, resulted in a reduction of egg hatch from 85.9% in the unreleased plot to 17.0% in the released plot. (author)