What Can You Put Into Water to Kill Mosquitoes?

Updated April 17, 2017

Mosquitoes are a common pest, especially during the spring and summer months. To prevent pesky bug bites and the possibility of mosquito-borne illness, it is most effective to kill mosquito larvae at their youngest. The best method of prevention is to limit the amount of water pools available to egg-laying mosquitoes in your backyard by emptying old buckets, tires and plant holders. For small ponds and other ever-present bodies of water, treatment of the water may be your next best option.

Bacillus Thurigiensis Israelensis (Bti)

Bacillus thuringiensis israelensis, or Bti, is a compound found in most mosquito dunks products, which come in doughnut form and are sold at most hardware and garden centres. Bti is also in some mosquito granule products, which can be scattered throughout a small body of water. This compound is safe to other wildlife and ecology and is a natural bacteria that infects and kills mosquito larvae within a water source. The dosages are as follows:

Dunks: 1 dunk/100 sq ft of water; Lasts 30 days or more.

Granules: 1 tsp per 25 sq. ft. or 1 tbsp per 75 sq. ft. Every two weeks.


Methoprene can be found in granule form and is a juvenile growth hormone. Rather than a kill larvae, methoprene causes larvae to remain in an arrested state of juvenalia, thus preventing them from growing into mosquitoes. Methoprene is also used in small doses in certain foods to help control the possibility of bug infestation, and it is used in flea and tick medication.

Mosquito fish

Mosquito fish are the most natural way to alleviate mosquito infestations in small collections of water. Originally introduced in California in 1922, these fish have become a popular method for controlling waterborne bug infestations along the eastern and southern parts of the United States. The fish can eat mosquito larvae as quickly as they are produced, and also give live birth to their fish brood, after which these younger fish may also begin feeding. These fish are to be used only in contained bodies of water, rather than in natural habitats, because they have been shown to possibly destroy the eggs of amphibians in natural bodies of water such as lakes and ponds.

Natural household remedies

Olive oil has a suffocating effect on larvae in small bodies of water, and once added, will float to the surface of the water. By pouring enough oil to coat the surface of the water body, the larvae will no longer be able to have access to air and will therefore stop growing. This technique may be preferable for small water containment.

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About the Author

Emily Stokes graduated from Dickinson College with a B.A. in English and is pursuing graduate studies in writing at Sarah Lawrence College. Stokes has worked as a writing tutor at the Eberly Writing Center in Carlisle, Pa., and as a subcontracting writer for SKY University, LLC.