A Laboratory Bioassay Method to Assess the Use of Toxic Bait on Anastrepha fraterculus (Weidemann 1830).

The lack of standardization of bioassays for the evaluation of toxic bait toxicity on the South American fruit fly, Anastrepha fraterculus (Weidemann 1830), has led to erroneous interpretations of assay results. The objective of this study was to develop a methodology for the standardization and validation of toxicological tests on A. fraterculus toxic bait using the Success™ 0.02CB formulation (80 mg L-1 of spinosad). Anastrepha fraterculus adults, obtained from larvae reared on an artificial diet, showed higher susceptibility (LT50 = 48.96 h) than adults from larvae reared on cattley guava (LT50 = 53.83 h) and mango fruit (LT50 = 53.55 h). Anastrepha fraterculus adults at the age of five (LT50 = 65.30 h), 15 (LT50 = 59.01 h), and 30 (LT50 = 55.53 h) days presented similar toxicity. The consumption of toxic bait (4.74 mg) increased at 15 days, a fact also observed with insects without food deprivation. In addition, the absence of a food source (artificial diet) with the toxic bait significantly reduced adult mortality time by 7 h (LT50 = 57.42 h). In relation to exposure time, adults exposed to toxic bait for 1 h reduced consumption by 25%; however, they showed the same susceptibility as insects exposed to 2 (LT50 = 55.72 h), 4 (LT50 = 57.64 h), and 8 h (LT50 = 57.76 h). However, with 24 h of food deprivation, they had a higher susceptibility (LT50 = 46.48 h). Five-day-old A. fraterculus adults fed an artificial diet before being deprived of food for 12 or 24 h, then exposed to toxic bait for 4 h in the absence of a food source, are considered optimum conditions to evaluate the toxicity of toxic bait.