Mosquito Dunks® are an effective way to reduce mosquito larvae in your outdoor spaces. This 2-pack of Mosquito Dunks® slowly dissolves, releasing a bacterium that is toxic to all species of mosquito larvae. Each dunk covers up to 100 square feet of water, for up to 30 days, and is approved for use in organic production. Fight mosquitoes in any standing water, including rain barrels, bird baths, and more.