Determination of toxicity of insecticide combinations to Culex pipiens pallens

Objective To understand the effect of insecticide mixture in killing Culex pipiens pallens of different drug-resistant strains. Methods The standard bioassay recommended by WHO was employed and the effect of insecticide combinations on three resistant strains were determined. Results The combinations of propoxur plus acetophenate, propoxur plus cpermethrin, DDVP plus acetophenate showed relatively synergistic effect on the mosquito strains resistant to propoxur. The combinations of DDVP plus acetophenate, DDVP plus cpermethrin, propoxur plus acetophenate and propoxur plus cpermethrin showed relatively synergistic effect on the strains resistant to DDVP. Cpermethrin plus propoxur, cpermethrin plus DDVP, DDVP plus acetophenate and propoxur plus acetophenate showed relatively synergistic effect on strains resistant to cpermethrin. Conclusion Good mosquito -killing effect can be obtained by combined use of organophoshorous insecticides or carbamate when Culex pipiens pallens is resistant to insecticides.