Reducing insecticide runoff in urban waterways from perimeter ant treatments

Outdoor applications of insecticide barriers to control ants around urban structures are commonplace. Insecticides such as fipronil, bifenthrin, cyfluthrin and cypermethrin are regularly sampled from urban waterways. The presence of these insecticides has been attributed to perimeter sprays applied to control ants. Urban residences were treated with fipronil and bifenthrin to control ants and the amount of insecticide in the water runoff was determined. Various perimeter treatments of bifenthrin produced water samples with levels toxic to water fleas Daphnia. Similar treatments with fipronil did not result in water samples lethal to water fleas. The amount of insecticide runoff was significantly reduced by applying targeted applications around the structure. Granular applications also reduced the amount of bifenthrin in the water runoff.