Abstract: The effect on development of resistance in the housefly Musca domestica vieina Macquart on deltamethrin alone and mixtures of deltamethrin and phoxim by continuous selection was studied in the laboratory. All mixtures markedly lowered the level of resistance than deltamethrin or phoxin applied alone and no notable changes in sensitivity were observed even after selection for 18 generations. The suppressive effect was due to reduction of selection pressure of each insecticide in the comb ination on respective generations and synergistic action between deltamethrin and phoxim in the mixture. The most effective combination of deltamethrin and phoxim was found to be l:l(w/w) for deltamethrin resistance strain and l:1000(w/w) for phoxim resistance strain. All strains of the housefly selected by the mixture displayed almost no resistance to the initial single insecticide, either deltamethrin or phoxim. The metabolic mechanism of selected strains of house fly was investigated through testing the activities of detoxification enzyme and ACHE.

Key words: Musca domestica vicina. Macquart, insecticide mixture, insecticide, resistance