Quality Control of the Oriental Fruit Fly Dacus dorsalis in Sterile Insect Technique Programme

Abstract

Control or eradication of the oriental fruit fly, Dacus dorsalis Hendel, by the use of the sterile insect technique requires rearing, sterilizing and releasing large numbers of flies. Precautions must be taken that the rearing and handling procedures result in the efficent production of effective flies for this technique to be successt. This study was conducted to reveal the quality of mass-produced insects and some radiation effects of sterilizing dose on mating propensity and flight ability of flies. Oriental fruit flies were irradiated with 80 grays of gamma radiation from a cobalt-60 source as pupae 2 days before eclosion and irradiated pupae were marked with signal green dye. The mating propensity test was conducted in a 30 x 30 x 40 cm. plastic cage. Samples of unirradiated and sterile flies were sexed within a week after emergence and maintained seperately until they reached sexual maturity. During the 10th-14th days, twenty five pairs of the different groups (unirradiated males + unirradiated females, irradiated males + irradiated fermales, irradiated males + unirradiated females and irradiated femles + unirradiated males) were released into plastic cages. Mating pairs were removed and recorded at 10-min intervals. The total period of the test was in one hour and the number of pairs fromed at each interval was multiplied by a weighing factor. This gives a mean mating index which shows how fast the flies mated. The result indicated that there were no significantly different (P = 0.05) in mating propensity between both sexes of unirradiated flies andirradiated flies, unirrradiated males and irradiated males, and unirradiated females and irradiated females. In addition, the mating propensity increased with age of both unirradiated and irradiated flies. The fight ability test was conducted by placing 100 pupae in a 13x13 cm. cylindrical plastic container for emergence. Then, 1-day-old flies were released from plastic container. The result showed that there were not significantly different (P-0.05) in flight ability between unirradiated and irradiated flies.