Kill mosquitoes before they are old enough to bite! Mosquito Dunks® are made of a biological insecticide (BTI) that is toxic to all species of mosquito larvae including of mosquitoes that may transmit West Nile Virus Zika Virus and Dengue Fever. The only sustained release product with BTI Dunks kill mosquito larvae for 30 days. Place a Dunk in standing water where mosquitoes breed. Each Dunk treats 100 square feet of surface water regardless of depth. For less water Dunks can be broken into halves or quarters. Labeled for organic gardening by the USEPA. Highly effective low impact product. Non-toxic to all other wildlife pets fish and humans.