Kills mosquitoes before they're old enough to bite. The Mosquito Dunks are America's best selling home owner mosquito control product. The only product with BTI, a bacteria toxic only to mosquito larvae, that lasts 30 days and treats 100 square feet of surface water. Non-toxic to all other wildlife , pets, fish, and humans. Simply apply Mosquito Dunks to any standing water, or water garden. Kills within hours lasts for 30 days or more. Labeled For Organic Gardening by the USEPA. Highly effective low impact product.