Silicon dioxide damages the protective waxy layer of insect body and insects die due to desiccation. But, it is slow acting insecticide and effective at high dose, so it is used in combination with different insecticides.The under taken project focuses on the laboratory bioassay of Twenty different ratios between insecticide and silicon dioxide ranging from 1:0.0025 to 1:3 against adult female and ovisac stage.The mortality at adult female and egg sac stage, as well as quantity of wax removed was recorded.Intensity of synergistic effect on the toxicity of insecticides against mealybug's stages increased with increasing concentrations of silicon dioxide.The treatments, having silicon dioxide admixed with insecticides, removed many fold wax from the body of adult female than the treatments having only insecticides.Percentage mortality was found higher in the adult female as well as at ovisac stage at higher ratio and maximum at 1:3 (insecticide: silicon dioxide). The findings of the endeavour persuaded the coadministration of silicon dioxide with insecticides to synergize their toxicity as well as for the knockdown control of cotton mealybug at adult female and ovisac stage.