Evaluation of Effectiveness and Environmental Fate of Methoprene for West Nile Virus Management

The occurrence of vector-borne West Nile virus in North America has prompted the use of chemical larvicides such as methoprene for widespread urban mosquito control. Since 2003, municipalities in southern Ontario have applied methoprene pellets or ingots to storm water catch basins over the summer. Ryerson University studied the fate and transport of methoprene from a storm sewer system to its receiving water by conducting three years of field monitoring study. It was found that the residual concentrations of methoprene in the studied catch basins could fall below the required level for larvae control after rainfalls. On the other hand, the concentrations of methoprene at the sewer outfall were below the toxic level that could cause ecosystem damage.