Effect of spinosad on adults of Tribolium castaneum (Col: Tenebrionidae) and Sitophilus oryzae (Col: Curculionidae).

Toxicity of spinosad on adults of Tribolium castaneum Herbst (Col: Tenebrionidae) and Sitophilus oryzae L. (Col: Curculionidae) at different temperatures and exposure intervals was evaluated. A commercial formulation of spinosad, Tracer was used, against 7-14-day-old adults of rice weevil and red flour beetle. Bioassays were conducted at 24, 28 and 32 degrees C and 65+/-5% RH. Mortality was recorded at 24, 48 and 72 h post-treatment. Spinosad was diluted with water for making appropriate dosages. A control group (distilled water) was included in each bioassay. A dose-dependent response was observed in both species. Similar trend was detected between mortality and time intervals. In both species an inverse relationship between LD50 values and temperature was detected. Based on LD50 values and none overlapping of 95% CL, S. oryzae was more susceptible to spinosad than T. castaneum.