Southern California Prepares for a Mosquito Boom

For the first time in years, Orange County will spray pesticide in wetlands areas to kill off mosquito larvae that could be carrying diseases harmful to humans, like West Nile virus. This year’s heavy rains in Southern California brought a bumper crop of our most-hated insects.

In the lab at the Orange County Mosquito and Vector Control District, lab technician Sokanary Sun uses tweezers to fill a vial with dead mosquitoes.

“So here’s one pool of 50,” Sun said as she dropped the last of a heap of tiny corpses into the vial. The mosquitoes were caught in a trap at a Brea cemetery.

“We test them for all three viruses, which include West Nile Virus, western equine encephalomyelitis and St. Louis encephalitis,” she said.

Those last two viruses are pretty rare in SoCal, but Orange County has seen an increase in West Nile virus. Nineteen people have died since 2014 after being infected with the virus, according to Mary-Joy Cuburn, a spokeswoman for the vector control district.

Last year, 442 cases of West Nile virus were detected in humans throughout California -- and 151 of them in Los Angeles, according to the state Department of Health. The Zika virus, which can cause birth defects, has also been found here in recent years.

The OC vector control district is spraying five marshy areas in the hills around Orange after staff collected more than twice as many mosquitoes in March than the average during that month for the past five years.

Other parts of Southern California are also gearing up for a buggy spring and summer, though nearby districts said they haven’t yet seen a major uptick in the mosquito population.

Levy Sun, a spokesperson for the Greater Los Angeles County Vector Control District, said staff is focused on spraying in backyards and other urban settings where standing water creates “a ticking timebomb of mosquitoes.”

Charles Genkel, manager of Ventura County’s vector control program, said the first field crews were hired this week to seek out and spray sources of mosquito larvae.

"We rely heavily on public complaints” to identify mosquito larvae sources, he said.

How can you protect yourself? Officials recommend wearing mosquito repellent when outdoors, maintaining screens on doors and windows, and getting rid of standing water near your home.

Dottie Ellis, program chief of the Riverside County Vector Control Program, recommended that people scrub old tires and toys left outside before dumping them. The mosquitoes that carry Zika lay their eggs on surfaces like those.