Pyrethroids are long-lived, synthetic pesticides that interfere with the function of an organism’s nervous system. They kill a wide variety of insect pests, including ants, cockroaches, and lawn grubs, but also earthworms and beneficial insects such as ladybugs and lacewings. When pyrethroids end up in our waters, they can kill crustaceans, aquatic insects, and fish.
Products containing pyrethroids have active ingredient names typically ending in “-thrin,” including permethrin, bifenthrin, cyfluthrin, beta-cyfluthrin, cypermethrin, deltamethrin, lambda-cyhalothrin, and tralomethrin. An exception is esfenvalerate.