Tests were conducted to compare the effectiveness of methoprene (Altosid SR-10) as a water solution with an experimental wettable powder, ZPA-1019 containing 10% Altosid, against Culex quinquefasciatus Say in septic ditches. Both formulations were evaluated at rates of 0.011, 0.022, and 0.038 kg AI/ha rates were too low for both formulations to effectively control Cx. quinquefasciatus in septic ditches. Mortality of larvae exposed to ZPA-1019 at 0.038 kg AI/ha was 63% after 8 days. This decreased to 37% on the 10th day. Mortality of larvae exposed to Altosid SR-10 at 0.038 kg AI/ha ranged from 100-89.5% up to 12 days after treatment.