Trials to Establish Quality Control Method of Mass-Reared and Irradiated Flies in the Field

Abstract

To establish quality control method of the mass-reared and irradiated melon flies, Dacus cucurbitae, in the field, two preliminary tests have been done with mark-release-recapture method. The survival rate, dispersal and orientation ability to the places where wild flies were located, of the mass-reared and irradiated flies were examined in summer, 1985. Thirty Steiner type traps (Steiner 1957) baited with cue-lure and naled were distributed within a radius of 1200 m. The recapture rate and the total abundance of the males irradiated with a dose of 70 Gy at −3 days adult, which were the dose and the day of irradiation used in our eradication project, were fewer than those of the males irradiated with a dose of 70 Gy at −2 days adult and those of males untreated. Total abundance of the males irradiated with a dose of 70 Gy at −3 days adult in the two tests were almost same. The dispersal pattern and the decline of survival rate of the flies in Test 1 were different from those in Test 2. It did not always follow that the catches of released males depend on the distance of the trap from the release site within the same annulus, although the average catches of annulus decreased as the distance between the trap and the release site increased. The tendencies that more released males were caught in the traps which graded high in wild catches than that graded low, were observed within the same annulus.