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Mosquitoes can thrive despite drought conditions

Are your water conservation methods producing mosquitoes?

As residents of Marin and Sonoma counties brace themselves for another drought year, officials from the Marin/Sonoma Mosquito and Vector Control District urge residents not to let their guard down when it comes to mosquitoes.

“Mosquito production during drought years does not necessarily decrease,” stated Dr. Kelly Liebman, Scientific Programs Manager for the Marin/Sonoma Mosquito and Vector Control District. “Sources of ponded water still exist during a drought. The organic content in the water tends to increase the longer the water persists. This is an ideal environment for mosquitoes to grow.”

During a typical non-drought year, free flowing creeks generally do not produce mosquitoes. However, when rainfall is minimal the water in creeks ponds and becomes an ideal environment for mosquitoes to propagate. These puddles also serve as water sources for birds, which can carry West Nile virus and infect mosquitoes that bite them. When large populations of birds and mosquitoes congregate, the risk of West Nile virus transmission increases.

Water conservation methods may also contribute to mosquito production in neighborhoods. It is imperative that water storage containers are mosquito-proofed and checked on a regular basis to confirm that there are no leaks or openings where mosquitoes can gain access.

Follow these simple mosquito-proofing tips for water conservation containers:

  • Cover tightly with a lid or fine mesh screen (1/16 inch).
  • Inspect on a regular basis to be sure there are no cracks or leaks and that all seals and fittings remain intact.
  • Cisterns (above and below ground) should be completely enclosed with no openings to the outside environment.
  • Cover all inlets, outlets, and vents with fine mesh screening (1/16 inch).
  • Stock containers (with at least 18 inches of water) with mosquitofish.
  • Ensure that all storage containers are free of organic material such as leaves and debris.
  • Click here to learn more about ways to reduce, reuse, and recycle water responsibly.
three barrels two x'd out because they do not have covers and one that is covered
The first two water conservation/collection containers are great examples of how NOT store water.

For more information or to report mosquito issues contact the Marin/Sonoma Mosquito and Vector Control District at 707-285-2200 or online at

The Marin/Sonoma Mosquito and Vector Control District's programs and services are funded through property taxes and benefit assessments and are provided at no additional cost to all residents of Marin and Sonoma counties.

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