Species-Specific Toxicity of Certain Insecticides to Tephritids in Hawaii Suggested by Unusual Susceptibility Relationships Among Oriental Fruit Flies, Melon Flies, and Mediterranean Fruit Flies13

Abstract

For the past 17 years almost all insecticides evaluated at Honolulu, Hawaii, against the oriental fruit fly, Dacus dorsalis Hendel; the melon fly, D. cucurbitae Coquillett; and the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), showed interspecies toxicity relationships similar to those observed with malathion, the standard of comparison. This report notes 13 exceptions. Bay 22408 ( O,O -diethyl phosphorothioate O-ester with N hydroxynaphthalimide) was equal to malathion in toxicity to Mediterranean fruit fly, but was much less toxic than malathion to oriental fruit fly and melon fly. Conversely, Bay 19596 (ethyl (mercaptoacetyl) carbamate S -ester with O,O -diethyl phosphorodithioate), and Pyrolan® (3-methyl-1-phenyl-pyrazol-5-yl dimethylcarbamate), were equal to malathion in toxicity to oriental fruit fly and melon fly but were much less toxic than malathion to Mediterranean fruit fly. The closely related insecticides methyl parathion, dicapthon, and Chlorthion® ( O -(3-chloro-4-nitrophenyl) O,O -dimethyl phosphorothioate) were progressively less and less toxic, respectively, to all 3 species of fruit flies. However, melon fly showed an increasingly greater degree of resistance to these insecticides, in the order listed, than did the other 2 species.