Three toxicological bioassays were performed in two F1 south Brazilian field populations of Anastrepha fraterculus (Wied.). Lethal doses of fenthion (50% and 90%) were estimated in two bioassays, with oral administration, and with residual contact bioassay. Results of topical bioassays using fenthion diluted in alcohol, acetone or water were inconsistent. Samples treated with acetone or alcohol diluents presented high mortality (>10%), while the samples treated with water diluent showed a non linear response between dose and mortality. The residual contact bioassay was significatively more toxic when compared to a feeding bioassay, occurring equal slopes in males and females in the populations analysed. Additional test showed that insects did not discriminate between diets with and without fenthion.
Insecta; South American fruit fly; insecticide; toxicity
