Mosquito dunks float on water and will keep on working for 30 days or longer under typical environmental conditions. While floating; they slowly release a long-term; biological mosquito larvicide at the water's surface. This larvicide gradually settles in the water where it is eaten by mosquito larvae growing there. Mosquito Dunks may be used in all types of standing water sites where mosquito larvae grow. Alternate wetting and drying will not reduce their effectiveness. Directions Use one Mosquito Dunk for up to 100 square feet of water surface; regardless of depth. They can be used whole or broken into portions and applied to containerized standing water found near the home such as animal watering troughs; bird baths; flower pots; roof gutters; and water gardens. To prevent them from being washed away; the Dunks can be anchored using a string tied through the center hole; or they can be staked in place. Warning: Hazards to Humans: Avoid contact with eyes or open wounds. Environmental Hazards: Do not apply directly to treated; finished drinking water reservoirs or drinking water receptacles when the water is intended for human consumption.