304 - Storm water catch basins: The bane of mosquito control districts

Abstract: Catch basins, crucial for urban drainage, collect and convey storm water runoff, preventing flooding and maintaining water quality. These systems can be classified as either Municipal Separate Storm Sewer Systems (MS4s), which discharge directly into water bodies without treatment, or combined sewer systems, which direct runoff to sanitary sewers for treatment.

However, catch basins can become significant breeding sites for Culex mosquitoes, vectors of diseases like West Nile virus. Stagnant water, high organic matter, and warmer temperatures in these basins promote mosquito breeding. Additionally, debris and poor maintenance exacerbate mosquito production.

Controlling mosquitoes in storm water catch basins is time-consuming, labor-intensive, and costly. Urban areas may have 50,000 to 200,000 catch basins, while rural areas have fewer but more dispersed basins. Most mosquito control districts use one of four products: S-Methoprene, Spinosad, Bti, or Bacillus sphaericus. Increased research into larvicide resistance is revealing more about the challenges of effective mosquito control.