Abstract
Resistance of housefly to insecticides is considered among the serious prolems facing the workers in insect control. This phenomenon results due to frequent use of pesticides. This experiment was conducted to evaluate the selective pressure of azamethiphos and permethrin in changing resistance in housefly. Results showed that the resistance was developed faster in housefly strain when exposed to permethrin as compared to azamethiphos.The results also indicated that values of LD50 ratio was increased as the generation advanced.The values of LD50 of parent generations were 0.75 and 0.05 mu g / female as compared to sensitive strain which values were 0.03 and 0.008 mu g / female. In 10th generation, the LD50 was 2.81 and 1.44 mu g / female then increased to 6.14 and 4.46 mu g / female in 22nd generation.The resistance ratio was increased as generation advanced, the values were 25 and 6 in parent generations and increased to 93 and 180 folds in 10th generation to 204 and 557 folds in 22nd generation for azamethiphos and permethrin, respectively. In conclusion, the increase in resistance ratio varied according to the chemical group of pesticide.The importance of the tests related to insect resistance help in insects management in public health as transmitter for vectors to human and animals.