Head out to a grassy field as the sun goes down over Sacramento and you’ll be confronted by swarms of pests seeking their first blood meal of the year: mosquitoes.
The winged irritants are right on schedule, according to the Sacramento-Yolo Mosquito & Vector Control District. Warm temperatures bring mosquitoes out of hibernation weeks before spring starts, said district spokeswoman Luz Maria Robles. Those mosquitoes will lay the eggs that will hatch into the summer mosquito population.
“They’re getting ready to start laying eggs to start their life cycle,” Robles said. “With all the rain that we’ve had early this year, we have that combination of stagnant water and warm temperatures” that make good mosquito breeding grounds.
The mosquito district is asking residents to dump any standing water in their yards, such as rainfall lingering in buckets, tarps and stacked tires, Robles said.
Dr. Chris Barker, an associate professor with UC Davis’ School of Veterinary Medicine, said it’s too soon to tell if 2017 is going to be a bad year for mosquitoes.
He said a number of factors determine the severity of the mosquito season: when planting and irrigation begins for farmers; whether the city can flush out underground storm drains; and how much longer the rainy season lasts.
While Sacramento area residents may be seeing a lot of mosquitoes now, it’s because of warmer temperatures, not because of the heavy winter rainfall. The buzzing insects started their lives last summer in drainage ditches and irrigation channels.
“This time of year they tend to come out and seek blood,” he said. The species most prevalent this time of year is particularly noticeable because they like to bite mammals, he said. There are about 20 species of mosquito in the Sacramento region.
For now, the mosquito population will die down for a little while, he said.
“This time of year, the water is cooler so the development of mosquitoes is slower,” Barker said, which slows population growth. It can take a month for a mosquito to go from egg to adult. In the summer, that period can be as short as a week.
Robles said the district won’t start seeing West Nile virus until later this year, as the virus requires warmer weather to replicate. She said it’s a common misconception that there are fewer mosquitoes and therefore less exposure to West Nile virus during years of extreme drought. Instead, dry conditions forced mosquitoes and birds to concentrate around limited water sources, sending rates of West Nile virus soaring.
In 2014, the district sprayed insecticide from planes on three occasions throughout the summer months. Last June, the district sprayed Arden Arcade and Carmichael to combat the virus. By July, 52 mosquito samples and 20 dead birds tested positive for West Nile virus in Yolo County.
Robles said it’s too early to know how the virus will transmit this year.
“People think: There’s lots of water, we’re going to have more mosquitoes and more West Nile,” Robles said. “The water simply means there’s going to be a lot of areas for mosquito habitats.”