The acute toxicity of some inseticides to Scaptotrigona tubiba (Smith) was studied and the applicability of contact tests by topical application route and sprayed paper was discussed. Worker bees were captured in the beehive's entrance and divided by groups of four replies with five bees each one and kept in plates of Petri covered with filter paper for 48h, with food ad libtum. The inseticides were diluted with distilled water with increasing concentrations of active ingredients. In the test of sprayed paper, delthamethrin, trichlorfon and malathion showed a LC50 of 0,70; 0,26 and 0,015 ppm, respectively. B. thuringiensis had a LC50 higher than 336 ppm. For the topical application, delthamethrin, B. thuringiensis and trichlorfon showed the respective LD50 of 0,73; 115,29 and 0,08 mg/bee. A LD50 higher than 0,04 mg/bee was inferred for malathion. The importance of the sprayed paper method as a preliminary test for determining doses was evidenced, moreover to avoid the unnecessary bee contention and to reduce the experiment time. All the inseticides were considered highly toxic by topical application route except B. thuringiensis that was relatively nontoxic.
Insecta; stingless bees; acute toxicity; deltamethrin; organophosphorus insecticides; Bacillus thuringiensis
