The sterile insect technique and transmission of inherited sterility to control the diamondback moth, plutella xylostella (L.), and the cabbage webworm, Crocidolomia binotalis Zell

Two major cabbage insect pests, the diamondback moth (DBM), Plutella xylostella (L.), and the cabbage webworm (CWW), Crocidolomia binotalis Zell., have been studied intensively in relation to the possibility of insect control, either by using the sterile insect technique (SIT) or by transmission of inherited sterility. Four hundred and fifty moths each of P. xylostella and C. binotalis were sterilized with 0.30 and 0.40 kGy of gamma radiation, respectively. The irradiated insects, released into two laboratory cages (90 cm x 60 cm x 60 cm) containing 50 unirradiated moths, reduced the F1 population of P. xylostella and C. binotalis by 61.1 and 65.3%, respectively. In the field cage (2 m x 2 m x 2 m), the F1 population reductions in the respective insect species were 55.6 and 50.5%. Release of about 4500 irradiated C. binotalis into an experimental plot (15 m x 10 m) containing 500 normal moths reduced the F1 population by 41.02% in the dry season and 50.55% in the rainy season. Release of about 5000 irradiated P. xylostella into an experimental plot containing about 350 moths of a natural population resulted in a reduction in egg hatch of 85.9% in the unreleased plot and 17.0% in the released plot. Experiments on the F1 sterility of P. xylostella and C. binotalis were also conducted to explore the possibility of controlling these pests by using inherited sterility. In DBM, a substerilizing dose of 200 Gy resulted in considerable F1 sterility. Release of F1 inherited sterile DBM moths into population laboratory cages caused different levels of population suppression, depending on the irradiation dose. A substerilizing dose of 200 Gy induced inherited F1 sterility, which reduced the population by 22% in DBM. In C. binotalis, a substerilizing dose of 0.275 kGy was sufficient to induce inherited sterility, because the levels of sterility in the parent and in the F1 generation were 65.82 and 84.64%, respectively. (author). 8 refs, 6 tabs