County finds invasive container-breeding mosquito species in Winters

A field technician spraying foliage along Main Street. Photo by Crystal Apilado/Winters Express

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An invasive mosquito species with the potential to transmit Zika and other diseases was discovered in Winters last week, the first of its kind detected in Yolo County.

Luz Maria Robles, Public Information Officer for the Sacramento-Yolo Mosquito and Vector Control District, told the Express that as of Monday afternoon, 127 mosquito traps have been set around town. Sixty-nine of those traps caught adult invasive mosquitoes (each trap had varying amounts of mosquitoes between 1-10), but Robles said this is still considered widespread.

She reported that 12 different sites also had immature mosquito larvae developing in backyard containers

“The first traps that were set were on the southern side of the town and we are working our way to the north. We will continue to canvass the town over the next few weeks setting more traps,” Robles said. “Since we are seeing very widespread activity, we will also continue with our control operations. This means that we will do truck mounted fogging, our wide area larviciding and treatments to backyards as necessary. “

The first specimen that sounded the alarm, an adult female Aedes aegypti mosquito was found in a trap placed near East and Main streets last week.

“Finding this mosquito for the first time likely means it could possibly be established anywhere. We will continue to work diligently to look for and identify locations where these mosquitoes can be breeding,” said district manager Gary Goodman.

Robles said the invasive mosquitoes were first discovered in El Monte, California in 2011. They spread north and were found in Sacramento County for the first time in August of 2019 in Citrus Heights. She said the invasive mosquito brings the number of different mosquito species up to 24 the Sacramento and Yolo County areas.

Aedes aegypti are small, dark mosquitoes that lay eggs above the water line in small containers such as flower pots, pet dishes, bird baths, tin cans, tires, toys and other containers as small as a bottle cap. Robles said the eggs look like dirt and can survive even when the water in the container has evaporated. The mosquitos  also can be found under eaves of buildings and in green foliage like bushes and ivy ground covers.

Robles said the Aedes aegypti is an aggressive mosquito that prefers to bite people during the day and has the potential to transmit serious diseases including Zika, dengue and chikungunya.

The District is requesting the help of Yolo County residents to help identify them and to report instances of being bitten.

“We need your help,” said Goodman. “If you are being bitten throughout the day or notice more mosquitoes in your yard, please give the District a call to request a free inspection.”

Robles said she dropped off pamphlets and mosquito repellent wipes at both Winters City Hall and the Winters Chamber of Commerce locations for anyone who would like to pick some up. Community members can also request service for their businesses and homes on the district website.

Yolo County residents are also being urged to inspect their yards regularly and to make efforts to drain all sources of stagnant water, and to avoid over watering plants in pots.

Field technicians will continue to conduct door-to-door inspections looking for potential mosquito breeding sites, conduct appropriate treatments as necessary and talk to residents about preventive measures around their home. They are leaving pamphlets and informational door hangers to help spread knowledge about the invasive mosquitos.

As part of the District’s Integrated Pest Management program and Mosquito-Borne Disease Management Plan, they will administer Low Volume and Ultra Low Volume treatments by using ground and/or aerial equipment in and around areas where mosquito counts and virus activity have met treatment criteria.

The product applied by the District is designed to quickly reduce mosquito populations and to protect public health and welfare. All products are registered and evaluated by the California Environmental Protection Agency.

Residents who want to take additional action to reduce exposure, can take the following steps:

  • Remain indoors during applications in your immediate area.
  • Consult your doctor if you have special health conditions or concerns.

For a complete list of scheduled treatment locations by zip code visit

Residents can sign up to receive email notifications for truck mounted “ground spraying” treatments in their area online at When signing up, residents are able to specify which types of spray treatments they would like notifications on.

Different Treatment Types
The District performs different types of treatments in efforts to control mosquito populations.

Robles said currently they are doing “larviciding” (truck mounted ground spraying) treatments in Winters neighborhoods.

Larviciding treatments work to target immature mosquito larvae and pupae, before they are given an opportunity to develop into an adult mosquito. This type of spraying treatment usually happens in the early morning hours between 2-6 a.m.

Robles said the other type of ground spraying treatment being done in Winters targets adult mosquitoes. This type of spraying treatment usually happens around dusk from 7-10 p.m.

The option to sign up for text urban aerial spraying notifications on the District’s website only applies to West Nile Virus spraying treatments. Robles said that while agriculture spraying treatments are routine, the urban aerial spraying treatments are only done on an “as needed” basis. She said they have not done an urban aerial spray treatment so far this season, and did not do one last year either.

For additional treatment questions and answers please visit Spraying Frequently Asked Questions at

Residents experiencing mosquito bites during the day should report them immediately by calling 1-800-429-1022 or requesting service at

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