Effect of age, sex and time exposure of Anastrepha fraterculus (Wied.) to toxicity of fenthion was evaluated. The age of the flies was important to the appearance of the first intoxication symptoms; males and females of reproductive ages (30 and 60 days-old, respectively) were less susceptible to insecticide than flies in the remainder ages (four and 120 days-old). The effect of body weight on insect intoxication was not detected. LT 50 biossay with fenthion (varying from 3-7 minutes) showed a lower susceptibility of males than females at all ages. Adults of both sexes and 30 days-old submitted to continuous and discontinuous exposure to fenthion did not show toxic cumulative effect of the insecticide. The statistical analysis suggests a possible general detoxification mechanism (quantitative and/or qualitative) to fenthion sex-, age- and time-related. Once the species is highly mobile in nature we suggest that in fruit fly toxicological bioassays, these biological traits need to be observed in order to obtain more realistic data.
Insecta; fruit-fly; insecticide; toxicity
