TOXICITY OF AVERMECTINS TO LIRIOMYZA-TRIFOLII (DIPTERA, AGROMYZIDAE) LARVAE AND ADULTS

Toxicity of abamectin 0.15 emulsifiable concentrate (EC), abamectin 8,9-oxide 0.15 EC, and MK-0244 0.16 EC to Liriomyza trifolii (Burgess) larvae was determined by dipping cowpea, Vigna sinensis (Stickm), plants infested with early 2nd instars. Mortality was assessed at pupal development. Toxicity of abamectin and MK-0244 to adults was determined by allowing adults to feed for 24 h on a toxicant-10% sugar solution. Mortality was evaluated 24, 48, and 72 h after exposure. For larvae, the LC(50) value for abamectin was 0.053 ppm, which was 2.5 and 5.9 times more toxic than abamectin 8,9-oxide and MK-0244, respectively. Adult mortality was expressed sooner with abamectin than with MK-0244, but at 72 h after exposure, abamectin and MK-0244 were equally toxic. Larvae were more sensitive to avermectins than adults. Similar slopes were observed among avermectins in both larval and adult bioassays, implying quantitative differences in activity among avermectins. The potential use of the adult technique for resistance monitoring is discussed.