Drought may not ease threat from mosquitoes

  • Jeff Petersen, a vector control technician with the Marin/Sonoma Mosquito and Vector Control District, places mosquitofish (Gambusia affinis) into a pond in Anita Selinger's backyard in Santa Rosa, on Tuesday, May 13, 2014. (BETH SCHLANKER/ The Press Democrat)

The drought, which might fuel optimism regarding mosquitoes and the spread of West Nile virus, may actually be promoting growth of the insect's population, partly because of the widespread use of open rainwater collection containers.

That's the word from the Marin/Sonoma Mosquito & Vector Control District, which has seen a more than 20 percent rise in service requests for mosquito problems this season, compared to the same time last year, district spokeswoman Nizza Sequeira said.

District field personnel also have reported finding mosquito larvae in rain barrels and other containers in use without the kind of fine-mesh screens commonly employed to keep the insects out, district personnel said.

The fact that heavy mid-February rains were followed by warm weather also accounts for a sudden and early mosquito population boom, Sequeira said.

"We had the rains, and it warmed up, and they just blew up," said Jeff Petersen, a vector control technician with the district. Since then, "it's been steady."

Mosquitoes, pesky even without the potential for certain species to carry West Nile virus and other diseases, breed in standing water and thrive when it's warm. Population changes are directly tied to weather.

Unfortunately, some people doing the right thing by saving water to offset the lack of rain may be contributing, inadvertently, to a bumper crop of bugs.

State health officials recommend all rain catchment basins or containers be covered or screened.

Even without any notable change from seasonal weather patterns, it's a good idea to keep a running inventory of potential breeding spots and take measures to avoid helping mosquitoes reproduce, officials said.

The local vector control district, funded by property taxes, provides a variety of free interventions, including small mosquitofish that prey on the larva that can be deployed in decorative ponds to keep mosquito populations down.

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