The domestic mosquito Culex pipiens (Diptera: Culicidae) is one of the most important public health pests spread in Egypt. So the aim of this research was to study toxicological effect of some organic and bio-pesticides on adult instar of the domestic mosquito that collected from different location of Cairo Governorate in Egypt, during the period of 2020-2022 in Toxicology Enviromental Research Unit, Faculty of   Agriculture, Ain Shams University. We use three organic Insecticides (Chlorpyrifos, Lambda-cyhalothrin , Imidaclopride) and two bio-Insecticide (Emamectin benzoate, Spinosad) at different concentrations (0.01, 0.1 and 1ppm) were applied on mosquito adult. It was recorded the value of LC_50,  toxicity and the resistance rate to different pesticides on the field and Susceptible strains after 24 hours of treatment. The result showed the highest effect on the East strain then the North strain to Chlorpyrifos. In the case of the Lambda - cyhalothrin had the highest resistance in the South strain. In Imidacloprid was the resistance rate high  in the South strain, and Emanating benzoate has higher in the resistance in the East strain, while, Spinosad recorded higher resistance in the South strain compared to The Susceptible  strain. The relative Potency of Spinosad was higher in all strains on adult of culex pipiens. Spinosad was higher in toxicity index to the adult mosquitoes compared to other pesticides.
Keywords: Culex pipiens, Chlorpyrifos, Lambda-cyhalothrin, Imidacloprid, Emamactin benzoate and Spinosad.