ABSTRACT
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.
Subject(s)
Biological Assay , Insecticides , Macrolides , Tephritidae , Toxicity Tests/standards , Animals , Drug Combinations , Insect Control , Larva , Time FactorsABSTRACT
The development of appropriate methodologies for bioassays is of paramount importance to study the methodological factors that may interfere in the experimental design. Thus, laboratory bioassays have become increasingly important for the determination of data that are realistic and replicable. The objective of the study was to develop a bioassay methodology with the ready-to-use toxic bait Success™ 0.02CB, 96 mg L-1 of spinosad, in adults of Ceratitis capitata (Wiedemann) as a study model. The insect origin (laboratory population, LT50 = 11.16 h), time of toxic bait supply (4 h, LT50 = 16.85 h), food deprivation (12 h, LT50 = 15.55 h), and the adult age (5 days, LT50 = 35.31 h) of C. capitata showed higher susceptibility and a shorter LT50 lethal time to the Success™ 0.02CB toxic bait. However, the absence or presence of a food source (LT50 ≈ 31.17 h) during the bioassay did not affect the susceptibility of C. capitata. Further, adults of C. capitata who were deprived and in the absence of a food source (artificial diet) had higher consumption of toxic baits (mg) during treatment exposure. The use of a 12-h deprivation period, toxic baits offered for 4 h, and absence of an artificial diet for adults of C. capitata at 5 days of age during the bioassay are considered adequate for evaluating formulations of toxic baits under laboratory conditions.
