Present study was designed to investigate the role of non-specific esterases, glutathione-S-transferesaes and monooxygenases in insecticide resistance in Bactocera zonat. Flies were collected from Gauva orchids of Ajnala, Sargodha. For biochemical estimation of detoxifying enzymes, flies were exposed to the selected insecticides (i.e. Trichlorofon, Malathion and λ-cyhalothrin) for one hour, and then shifted to clean jars. The activity of insecticide detoxifying enzymes in the survivors and

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... ol were compared. The activity of insecticide detoxifying enzymes was higher in survivors compared to the susceptible flies (control). The activity of beta esterases, glutathione S-transfereases and monooxygenases of Trichlorofon and Malathion treated flies did not differ. However, both groups have higher activities of detoxifying enzymes compared to the control. Higher activities of insecticide detoxifying enzymes in survivors compared to the control groups indicate the involvement of these enzymes in insecticide resistance.