Kills mosquitoes before they're old enough to bite The only product with bti, bacteria toxic only to mosquito larvae Lasts for 30 days and treats 100 square feet of surface water Non-toxic to all other wildlife , pets, fish, and humans Labeled for organic gardening by the usepa Use Mosquito Dunks in any standing water including rain barrels, bird baths, tree holes, elevator shafts, planter reservoirs, rain gutters, etc