Experiments on the control of the olive fly, Dacus oleae (Gmel.), by the combined effect of insecticides and releases of gamma-ray sterilized insects.
The experiments described were carried out in 1973 and 1974 in three olive groves on the Kassandra peninsula in northern Greece. The fly population in this peninsula was smaller than in other parts of northern Greece, and was kept to a low level by a control technique in which bait-sprays of fenthion (Lebaycid) and phosphamidon (Dimecron) were followed by releases of laboratory-reared flies sterilised by treatment with gamma -radiation at a dose of 9.5 krad. Fenthion was used in the first spray, phosphamidon was applied three weeks later, and releases of sterilised flies were begun after a further two weeks and repeated weekly, a technique of ground release being used. In the first year sterilisation was carried out in the adult stage, and in the second in the pupal stage. The releases were begun before the fruits became suitable for oviposition and were continued until cold weather in November stopped fly activity. Good control was achieved by these methods, but the timing of the sprays and releases was critical for success. Trouble was caused in the first year by fungus infection of the fruits resulting from excessive puncturing by the released females. This did not occur in the second year because the insects had been sterilised in the pupal stage and did not produce eggs.