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) l arvae was determined by dipping cowpea, Vigna sinensis (Stickm), plant s infested with early 2nd instars. Mortality was assessed at pupal dev elopment. Toxicity of abamectin and MK-0244 to adults was determined b y allowing adults to feed for 24 h on a toxicant-10% sugar solution. M ortality was evaluated 24, 48, and 72 h after exposure. For larvae, th e LC(50) value for abamectin was 0.053 ppm, which was 2.5 and 5.9 time s 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. Larv ae were more sensitive to avermectins than adults. Similar slopes were observed among avermectins in both larval and adult bioassays, implyi ng quantitative differences in activity among avermectins. The potenti al use of the adult technique for resistance monitoring is discussed.