Malathion Bait Consumption and Mortality of Anastrepha suspensa (Diptera: Tephritidae)

We examined the consumption and oral toxicity of malathion bait to Anastrepha suspensa (Loew) (Diptera: Tephritidae) in a laboratory setting. Based on the malathion concentration in the bait and quantity of bait consumed, the malathion dose increased as bait malathion content increased. Mortality was about the same comparing 100 and 200,000 ppm malathion, but percentage of feeding was up to 7 times less for 200,000 ppm malathion. Approximately 10% of males and females survived in these tests, suggesting that the laboratory population of A. suspensa contains individuals resistant to malathion and malathion manufacture by-products. Solid phase microextraction collection and gas chromatography-mass spectrometry of volatile compounds suggest that malathion formulation contaminants were responsible for the mortality of flies that had no demonstrable contact with the malathion bait.