Toxicity of malathion and spinosad to Bactrocera zonata and Ceratitis capitata (Diptera: Tephritidae)

Recently, an outbreak of the peach fruit fly, Bactrocera zonata (Saunders) (Diptera: Tephritidae), in the metropolitan area of Tel Aviv in central Israel was reported. The default action taken in response was the intensive use of the male attractant methyl eugenol applied together with the organophosphate insecticide malathion, which is toxic to a wide range of insects. In agricultural groves, the spinosad bait formulation GF-120 (TM) is routinely used to control the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). In this study, we evaluated the toxicity of malathion and spinosad to B. zonata and C. capitata in Israel following both contact exposure (tactile) and feeding (insecticides mixed with bait). Whereas doses of 1,000 and 2,000 ppm of malathion were highly toxic to C. capitata both upon contact and when eaten with bait, a dose of 10,000 ppm (1%) caused only 10 to 35% mortality of B. zonata. This insensitivity to the toxicant cannot be explained by feeding avoidance. On the other hand, the toxicity of spinosad to B. zonata was high with LC80, LC90, and LC99 values of 12.28, 17.67, and 33.62 ppm, respectively. This result suggests that the spinosadbased control measures routinely taken against C. capitata in Israel could be effective against B. zonata.