General information

Frequently Asked Questions about Larval Mosquito Control

How much water do mosquitoes need to breed?

Even very small amounts of water can provide enough space for mosquito larvae. Some mosquito species need as little as a bottle cap full of water to reproduce!

How long does it take for mosquitoes to breed?

Under the right conditions, it can take as little as a week for mosquito larvae to emerge as adults. In general, warmer weather means faster development.

What are mosquito fish?

Mosquito fish are small fish related to guppies. They are used for mosquito control in ornamental ponds, livestock troughs, and other manmade water sources. Mosquito fish cannot be used in natural water sources.

How do I take care of my mosquito fish?

Once stocked in an appropriately-prepared pond, mosquito fish don’t need much care. You can learn how to keep your mosquito fish healthy here.

What can I do if I suspect my neighbor is breeding mosquitoes?

First, talk to your neighbor. They may not be aware that the standing water on their property is a problem. If you don’t feel comfortable approaching your neighbor, or if you notice a problem with an unoccupied property, please give us a call at (650) 344-8592.

Are larvicidal treatments safe for my mosquito fish?

Yes. Larvicides are effective only against mosquito larvae.

Is it safe for animals to drink water treated with larvicides?

Yes. Larvicides are effective only against mosquito larvae.

What kind of water sources do mosquitoes breed in?

Different mosquito species prefer different kinds of standing water, but in general, mosquitoes will breed wherever there is standing water. Common sources include containers and plant saucers, birdbaths, neglected swimming pools, stagnant ditches and creeks, and marshes.

If you control mosquito larvae why do you still have to control adult mosquitoes?

The District is very effective at eliminating mosquito breeding sites, but it is impossible to find and treat ALL the standing water in the entire county. For example, some standing water might be under buildings where we can’t see it, or in someone’s locked backyard.

Usually it’s sufficient to reduce the mosquito population by treating all the standing water we do have access to, but if we discover that there are adult mosquitoes infected with a disease that can be transmitted to humans, it’s important to quickly eliminate them before anyone gets sick. When that happens, we may conduct an adult mosquito control treatment.

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