Selective toxicity of insecticides between Aphis citricola and Coccinella septempunctala

The selective toxicity of 15 insecticides between Aphis citricola von der Goot and Coccinella septempunctala L.was investigated with a topical application method recommended by FAO.The results show that the selective toxicity of imidacloprid is the highest among 15 insecticides tested, and its selective toxicity ratio(STR, ladybird LD₅₀/aphid LD₅₀)is 135.56. Other insecticides with higher selective toxicity are cyfluthrin, cypermethrin and malathion, of which STRs are 114.00, 62.86 and 45.43, respectivly. Therefore these insectivides,such as imidacloprid, cyfluthrin and malathion, show a higher toxicity to the aphid but safe for the natural enemay ladybird. They coulud be selected as a relatively idael alternative for integrated chemcial and biological control of aphids in the field.