A perfect storm for Petaluma-area mosquitoes

For the past several years, Kate Collins has taken her golden retriever Toby on walks around Shollenberger Park a couple evenings per week. But lately those walks have been getting earlier in the day, while the sun is still high in the sky.

Collins, 64, said she purposefully avoids walking in the park in the evenings.

“The mosquitoes are worse in the evening,” she said. “It’s gotten worse this year.”

Indeed, a confluence of weather factors have combined to create a perfect storm for mosquito propagation, according to officials who deal with the pests. An El Niño-fueled wet winter on top of four years of drought has left lakes of standing water, where mosquitoes love to breed, near Petaluma and other North Bay locations.

The recent warm weather has created an explosion of mosquito activity unlike any season in the past decade, said Nizza Sequeira, Public Relations Director for the Marin-Sonoma Mosquito and Vector Control District.

“With all of the rain we have experienced, there are a lot of areas that are now holding water, which means more mosquitoes,” she said.

The wetlands around Shollenberger Park are ground zero for mosquito activity, she said. The salt marsh mosquitoes, which are endemic to the lowlands just south of Petaluma, are especially problematic because they can fly up to 20 miles, meaning they can cover an area the size of the city.

“They are extremely aggressive biters, can emerge as adults by the thousands and cause extreme discomfort and potential injury to residents,” Sequeira said in a statement. “These mosquitoes are being found in high numbers in large areas such as wetlands and marshes adjacent to schools and subdivisions.”

The mosquito control district has seen calls for service increase by 112 percent from last year, she said. District technicians will come to a resident’s home and check for mosquito breeding grounds, usually in standing water. They can set mosquito traps, or stock a resident’s pond with mosquito-eating fish, Sequeira said.

Officials have not found any cases of West Nile Virus in the area this year, she said, but last year one person and 12 mosquitoes tested positive for the virus that causes fever and headaches. The Zika Virus, which has infected thousands in South and Central America, has not been detected in California, although the mosquitoes that carry the virus have turned up from Southern California north up to San Mateo.

The treehole mosquito, which is found in Sonoma County, doesn’t spread disease to humans, but is a vector for dog heartworm, Sequeira said.

The best measures to combat mosquito bites are to apply bug spray or sleep under an oscillating, she said.

“Check your yard for standing water,” she said. “Make sure septic tanks and rain barrels are screened. And don’t over water.”

(Contact Matt Brown at matt.brown@arguscourier.com.)