Laboratory studies were conducted to determine the mortalities caused by spinosad in Ceratitis capitata (Wied.) and Anastrepha fraterculus (Wied.). Spinosad formulated bait, diluted in water, was compared with baits of malathion, trichlorfon, fenthion and deltamethrin. The lethal time increased for C. capitata (medfly) adults fed in lower concentrations of spinosad. The LT50 values for C. capitata were estimated in 106, 126 and 154 min for 80, 8 and 4 ppm, respectively. No differences at LT50 were observed for different ages, 2-3d, 3-5d and 5-7d old C. capitata exposed to 80 ppm. Both fruit fly species presented similar pattern of survival when treated with spinosad at 80 ppm. In general, fenthion and trichlorfon showed LT50 values lower than spinosad for different ages of medfly. After 180 min from initial exposure to spinosad bait, the mortality rates of 2-3d and 3-5d old C. capitata were similar to that by fenthion. The LT50 for A. fraterculus was estimated in 85.9 min, slightly shorter than for C. capitata when both species were exposed to 8 ppm of spinosad. Medfly adults exposed to concentrations equal or inferior to 0.4 ppm of spinosad showed LT50s longer than 12 h. Leaves treated and kept in the field with baits of spinosad, malathion, fenthion and deltamethrin, caused high mortalities of medfly adults until two days after treatment.
Insecta; fruit fly; insecticide; mortality
