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Mosquito Larvae 

- The most effective way to avoid bites is to control larvae -

Summary: Controlling mosquito larvae is the best way to reduce mosquito bites and the diseases that mosquitoes spread. Standing water sources, where larvae develop, should be drained or treated.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)

Drain standing water

Sounds simple but it is true -- the best way to eliminate biting mosquitoes is to eliminate mosquito larvae (right). Mosquito larvae develop in standing water and even a small volume of water can support large numbers of larvae.

Landscape planters, fountains and ponds should be checked regularly for mosquito larvae. Larvae will appear as small wriggling "worms" attached to the surface (right) or swimming near the bottom. Small containers should be drained or at least flushed and refilled about once a week during warm summer months. Eliminating sources of standing water, including rain gutters, will significantly reduce the number of biting mosquitoes and the chances of getting a disease like West Nile virus.

yellow fever mosquito larvae

Yellow fever mosquito larvae suspended, head down, from water surface by siphon tubes.


Treat standing water

You can treat standing water to control mosquito larvae with a bacterial insecticide called Bti (shorthand for Bacillus thurengiensis israeliensis). This bacterium is highly specific for mosquito and black fly larvae and won't harm plants, fish or other animals that drink the water.

Treat only permanent bodies of water that can't be drained or flushed such as ponds or large fountains. Bti should be applied to water as granules (callled "bits") or pressed cakes (called "dunks") which dissolve releasing the mosquito-attacking bacterium. If dunks are used in horse troughs they should be sunk with a weight to keep them out of reach of animals.

Bti bits and dunks, as well as other mosquito control products, can be found here: Mosquito Control (DoMyOwnPestControl).


What about adult mosquitoes?

First of all don't use black light "bug zappers" for mosquitoes (see Related Articles below). These traps may actually make matters worse because they draw mosquitoes into the area. Black light traps also indiscriminately kill beneficial insect species. New propane-powered carbon dioxide traps are one way to capture and kill adult mosquitoes without using insecticides but they are not effective in every situation.  These traps do not impact beneficial insects the way bug zapper traps do (see Using Propane Mosquito Traps).

The best way to protect yourself from adult mosquitoes and other biting flies is to use insect repellent. There are now effective long-lasting alternatives to DEET (see Using Insect Repellents). Finally, contact your county board of health, or equivalent governmental body, and talk to them about setting up a regional vector control district in your area.

Related Articles

What are Mosquitoes?

Are Black Light Traps Effective?

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Jack DeAngelis, PhD,  , email:  [email protected]

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