Adult mosquitoes cannot be killed with bleach. However, mosquito larvae can be killed by bleach. It is not recommended to spray bleach at adult mosquitoes.
Bleach is legally considered a pesticide. The U.S. Environmental Protection Agency states that any bleach with a minimum of 5.25 percent sodium hypochlorite that kills bacteria and kills fungi is a pesticide. Mosquitoes need standing water to breed. The best protection is to drain standing water or to turn the objects upside down to prevent water collection. If there is standing water, 1 tablespoon of bleach for every 50 gallons should suffice for killing mosquito larvae. Once a week, a bleach and water solution can be used to spray down the items on which standing water collects.