WATER CONSERVATION CAN CREATE MOSQUITO RISK

How to conserve water while preventing mosquitoes

Mosquitofish in this rain-filled wine barrel are a natural defense against mosquitoes.

Due to this year's extreme drought in California, citizens across the state are being asked to reduce water usage by at least 10 percent in many cities.  In some communities, city officials are mandating 20 percent reductions because despite a few storms this winter, there has not been enough rain to erase California's severe water deficit.

Without the option to use sprinklers or garden hoses to wash cars or water lawns and plants, many residents may be looking for a mechanism that allows them to save rainwater such as a rainwater diverter, tarp, or barrel. While these items can be important ways to maintain green foliage or even clean a dirty car, standing water is the number one way to create a risk of mosquito-borne illness. 

Female mosquitoes with the ability to transmit West Nile virus can lay up to 400 eggs at a time in just two tablespoons of standing water. In warm weather, those eggs can take just five days to develop into adult mosquitoes that have the ability to spread disease. The mosquitoes that can transmit dengue fever and yellow fever need even less water and can lay eggs in the tiny amount of water that can collect on a candy wrapper or other pieces of trash that aren't properly stored in a garbage can with a secure lid. If mosquitoes need just a spoonful of water to lay hundreds of eggs, imagine how many mosquitoes could come from a rain-filled ten foot tarp or 50 gallon water barrel.

That is why the Contra Costa Mosquito & Vector Control District is recommending folks take precautions to make sure conservation doesn't create a new risk of mosquitoes. A number of manufactured rainwater collection systems keep mosquito prevention in mind by designing the system to have limited openings that feature screens to prevent insects. These specialized barrels and systems usually feature a spigot that allows water to be drained without opening the container.

For those who don't want to buy something new and opt to use an existing barrel or container that is not especially made for rain collection, then the District recommends the following solutions to prevent mosquitoes:

• When using a bucket or container smaller than 30 gallons of water, use a product containing the biological mosquito larvicide Bacillus thuringiensis subspecies israelensis (B.t.i.) such has Mosquito Dunks® or Mosquito Bits®. B.t.i. is a naturally occurring bacteria that is deadly to mosquitoes, but is harmless to other living things.
• When using a container of at least 30 gallons of water, for example, a ˝ wine barrel planter, please visit the District to pick up free mosquito-eating fish. Each fish can eat up to 500 mosquito larvae per day. A barrel generally only needs about four fish.
• If the container that holds rainwater does not contain B.t.i. or mosquito fish, install a screen over any opening to prevent mosquitoes from having access to the water

Careful conservation now will allow residents to save rain water for the summer's plants, grass and dirty cars, without increasing the mosquito population along with the risk of mosquito-borne illness later.

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