Use of plastic formulations of chlorpyrifos and sumithion as mosquito larvicides and their delayed effects on the basal follicle numbers developed by female survivors

Tests were conducted to evaluate the larvicidal effectiveness of three controlled-release plastic formulations of both chlorpyrifos and sumithion against mosquito larvae ofCulex pipiens. Excellent control with 90–100% larval mortality was achieved for 85, 77, 73, and 64, 54, 48 days posttreatment by using the non-expanded, expanded and foamed formulations of chlorpyrifos and sumithion, respectively. Apart from lethal action, larval treatments with the above formulations led to an increase in the mean number of basal follicles developed by mosquito females which survived from these treatments. The increase in this mean per female was in respect 23.4, 30.0, 18.7% in case of chlorpyrifos formulations, and 21.8, 17.2, 26.8% in case of sumithion formulations.