When standing water cannot be drained, several low-toxicity products can be used to kill mosquito larvae before they become adults. A bacterial product, based on the microorganism Bacillus thuringiensis , is sold in the form of dunks, granules or doughnuts. These can be placed in ditches, underground catch basins or in other standing water areas where mosquitoes breed.
Products containing methoprene, sold under the trade names of Altosid or “Pre-Strike” are also good, especially for water that will remain for extended periods of time. Both products are safe for fish, birds and pets.