Worst mosquito infestation in years could soon hit Inland Empire

By David Downey | Contributing Writer

Heavy rain has transformed normally dry fields and numerous backyards across the Inland Empire into soggy breeding grounds for mosquitoes.

As a result, bug experts are bracing for what could be one of the region’s worst mosquito seasons in recent memory.

Eric Ballejos, public information and technology officer for the Northwest Mosquito and Vector Control District in Corona, said the stage is set for a “busy year.”

“When you have stagnant water you have mosquitoes, and there seems to be plenty of water right now,” Ballejos said.

Officials with San Bernardino County Public Health Department’s mosquito control program said in a news release last week that there is standing water in just about every neighborhood.

That hardly comes as a surprise.

Waves of storms have pelted the region repeatedly in winter and spring.

Ontario, through Thursday, April 13, had recorded nearly 23 inches of rain since fall — a little more than twice average for this point in the season, said Brandt Maxwell, a National Weather Service forecaster in San Diego. Riverside’s almost 13 inches stood at about 50% higher than normal, he added.

Mosquito-control agencies throughout the Inland area have taken notice and are springing into action.

“We are definitely on high alert here,” said Brian Reisinger, community outreach coordinator for the Ontario-based West Valley Mosquito and Vector Control District.

San Bernardino County officials, in the news release, implored residents to help reduce the chance of a major infestation.

“We are anticipating a significant increase in the overall mosquito population,” Dr. Michael Sequeria, the county’s health officer, said in an email.

“It could be much worse if residents don’t dump standing water or report other potential mosquito breeding sources,” Sequeria said.

San Bernardino County officials also urge residents to repair pools and spas in poor condition, stock ponds with mosquito fish and equip doors and windows with tight-fitting screens.

The Northwest district, which serves 900,000 people in Corona, Norco, Jurupa Valley, Riverside, Lake Elsinore and Canyon Lake, is deploying a catchy phrase to enlist residents’ help: “tip, toss and take action.”

Northwest officials want people to look around their homes for anything that might have water in it and tip the water out, Ballejos said.

Officials urge homeowners to toss out those containers, if practical, to prevent them from becoming breeding grounds, he said. And they want residents to take action: report standing water in their neighborhoods and protect themselves with insect repellent.

It’s important to get rid of even the smallest item that could become a breeding ground for mosquitoes, officials said.

“We’ve found them inside of soda cans,” Reisinger, the West Valley outreach coordinator, said.

Don’t forget to check backyard drain pipes for standing water, too, officials said.

At Northwest, Ballejos said technicians are in the field inspecting and treating larger pools of water. So are workers for West Valley, which serves 650,000 people in a 200-square-mile area encompassing Ontario, Chino, Chino Hills, Rancho Cucamonga, Montclair and Upland.

One big concern is swimming pools green with algae, which “are notorious for breeding mosquitoes,” Reisinger said.

To get ahead of that problem, on Monday, April 10, a company hired by West Valley flew a plane over the district and snapped photos from several thousand feet above the ground, Reisinger said. Stark contrasts between healthy, light blue pools and dark green ones in poor repair stand out in the pictures.

The district will send letters asking homeowners to clean dirty pools, Reisinger said.

“In the event that folks don’t comply, we will be sending our technicians out,” he said. “We’re trying to attack these swimming pools early.”

So far, the mosquito problem is under control, thanks to a silver lining in all those storm clouds.

“The good thing is we’ve had unseasonably cool weather,” Reisinger said. “That’s been keeping our mosquito populations down.”

In West Valley’s service area, mosquito sightings for March were down 85% from the same month in 2022, Reisinger said.

The lack of activity could change in a hurry, however, with temperatures in the 80s lurking around the corner.

Ballejos said “calls for service directly relate to the temperature.”

When mosquitoes do emerge in a big way, their disruption to human activities will be aggravated by a recent trend, said Anandasankar Ray, a professor of molecular, cell and systems biology at UC Riverside.

It used to be that residents had to deal only with native Culex quinquefasciatus mosquitoes, which predictably bite early in the morning and in the evening, Ray said.

“In the past, if you were careful during dusk or dawn you were OK,” Ray said. “Now you have to start worrying about the daytime, too.”

Over the past several years, he said, the non-native species of Aedes aegypti, also known as the yellow fever mosquito, and Aedes albopictus, the Asian tiger mosquito, have put down roots in the Inland Empire. Unlike native varieties, these mosquitoes bite throughout the day, Ray said, making them “really annoying.”

Culex mosquitoes have been known to transmit diseases such as West Nile virus, Ray said. The newly arriving ones can spread yellow fever, dengue fever and Zika.

With both natives and non-natives, it’s the females that do the biting, not the males, Ray said. He said the female needs a “blood meal” to lay her eggs.

Ray added that those females can spot people from a distance through the carbon dioxide they expel during breathing.

“They can find you like a guided missile,” he said. “They are very good at smelling us out.”

They are also very good at finding watery places to lay eggs, too, he said.

Ray led a UCR study published earlier this year that showed promise for developing mosquito repellents using ammonia in higher concentrations than occur naturally in human sweat – to prevent a mosquito from finding someone to bite.

In a separate paper last year, Ray explored ways to block mosquitoes’ ability to sense humidity and locate standing water.

Perhaps one of the most amazing – and alarming – abilities of mosquitoes is their ability to breed in tiny amounts of water.

Ray said females can lay eggs in puddles as small as what would collect in a bottle cap, underscoring the importance of eliminating standing water wherever found.

It doesn’t help that mosquitoes are prolific at reproduction.

“A single female mosquito can lay hundreds of eggs in a single night,” Ray said.

FIGHTING MOSQUITOES

Here are some tips for preventing mosquitoes from ruining spring and summer activities

• Drain or dump standing water around the home, including birdbaths, old tires, buckets, flower pot saucers, clogged gutters and puddles from leaky sprinklers.
• Repair or drain pools, ponds and spas in poor working order. Use mosquito fish in ponds. Some agencies, such as San Bernardino County’s mosquito control program, offer free mosquito fish.
• Ensure screens on doors and windows are tight fitting. Repair those with tears and holes.
• Wear shoes, socks, pants, and long-sleeve shirts that are loose fitting when outdoors.
• Apply insect repellent containing DEET, Picaridin, IR3535, or oil of lemon eucalyptus.
• Report green pools and other breeding sources.

Source: San Bernardino County Environmental Health Services’ Mosquito and Vector Control Program