Species specificity among oriental fruit flies, melon flies, and Mediterranean fruit flies in susceptibility to insecticides at several loci.

Abstract

DDT, methoxychlor, and malathion were applied topically in Honolulu in 1957 and again in 1967 to the thoracic mesonotum and mesosternum, the abdominal mid-dorsum and mid-venter, and the verto-occiputal and oral regions of adult oriental fruit flies, Dacus dorsalis Hendel; melon flies, D. cucurbitae Conquillett; and Mediterranean fruit flies, Ceratitis capitata (Wiedemann). Species-specific differences in susceptibility to the same insecticides on identical loci were noted. The thoracic mesonotum of oriental and melon flies was the least susceptible of the 6 application regions to DDT or methoxychlor, while the thoracic mesonotum of Mediterranean fruit flies was the most susceptible. With melon flies, application of methoxychlor to the oral region was at least 200 limes more effective than application to the thoracic mesonotum. However, With Mediterranean fruit flies, application of methoxychlor to the oral region was 2 times less effective than application to the thoracic mesonotum. Locus-specific differences in susceptibility to different insecticides by the same species were noted also. DDT and methoxychlor were least effective when applied to the thoracic mesonotum of oriental and melon flies, as compared with the other 5 application regions. Malathion, however, was most effective when applied to the thoracic mesonotum of oriental or melon flies.