Four insecticides and 2 insect growth regulators (diflubenzuron and methoprene) were applied to anaerobic swine waste lagoons for the control of the mosquito Culex quinquefasciatus (Say). Chlorpyrifos at 0.4 Ib/acre (448 g/hectare) or more gave excellent mosquito control for 3-5 weeks. Malathion at 1.0 Ib/A (1.12 kg/ha.) did not give satisfactory control. Temephos at 0.5 Ib/A (560 g/ha) gave control for only 3-4 days. Flit MLO at 7 gal/A (65 liters/ha) gave satisfactory control for 3-4 days and was not effective at lower rates. Diflubenzuron at 0.1 Ib/A (112g/ha) gave satisfactory control for 1-2 weeks. Methoprene did not give satisfactory control at 0.4 Ib/A (448g/ha). A granular formulation of diflubenzuron was about equally effective as the wettable powder.