Yakima Valley mosquitoes worst in decade

Cody Jansen sloshes through a pasture, his rubber boots squishing in muddy puddles as he goes.

He dips a ladle into a tiny pool and looks closely. Little "wigglers" flip and flop in the water sample. Mosquito larvae.

He and his co-workers at the Benton County Mosquito Control District are hardly surprised. They visit this boggy pasture every week. It's one of their hot spots.

And those hot spots were even hotter this summer. Mosquito control agents say they are winding down from their busiest season in about a decade.

Perhaps fueled by abundant spring runoff that lasted late into the summer, the Yakima Valley mosquito population was one of the highest this year. Control districts burned through bacteria and chemicals. Workers fogged adult mosquitoes up to three or four times a week. Even the professionals received more bites for their pains.

Al Hubert, manager of the Yakima County Mosquito Control District, calls it one of the worst summers in his 27 years on the job.

"My phone was ringing off the hook," he says.

His counterpart at the Benton County Mosquito Control District noticed the same thing.

"We haven't seen this kind of mosquito activity for 10 years," says James Henriksen says, manager of the Benton County Mosquito Control District.

With more mosquitoes come more concerns about the West Nile virus.

The Yakima Valley and Columbia Basin area is home to about 19 species of mosquitoes. The few that carry West Nile were three times as populous this year, Henriksen says.

West Nile is carried by mosquitoes from birds to horses and humans. It has shown up in birds, horses and mosquitoes in Benton and Yakima counties this summer. Just Wednesday, the state Department of Health announced four birds from those two counties tested positive for the disease.

Laura Charters, an environmental health specialist for the Yakima Health District, says her agency plans to stop testing birds this year.

"We pretty much know it's all over the county," Charters says.

So far this year, only one person has contracted the virus. That was a woman in her 50s in King County. Health officials aren't sure where she got it. She had traveled to Oregon and Yakima County during the time she was likely exposed to it.

She showed no symptoms, which resemble the flu or the common cold with fevers, aches and a headache. About 20 percent of the people who have the virus develop symptoms. Only about 1 percent of those get severe illnesses, such as encephalitis or meningitis.

There is no cure for West Nile and a vaccine is only available for horses.

Mosquitoes have long been associated with disease. In the tropics, they spread malaria. In 1957, fears of an encephalitis outbreak like the one in the 1940s prompted the formation of the Benton County Mosquito Control District, one of the largest in the state today.

And don't blame irrigation. Mosquitoes have always been in the area and probably always will be. Even explorers Lewis and Clark complained about mosquitoes in the Columbia Basin. Their journal entries described rubbing bacon grease on their skin to ward off the bugs, and dogs howling and yipping in frustration at night.

Matt Hoefer, field supervisor for the Benton County district, has stepped through the ice puddles of a late spring frost and found mosquito larvae.

"I know that I've always got job security," he says.

Hoefer and his crews blame the high mosquito counts on last winter's healthy snowpack, which melted late. It left high water in the rivers and stagnant pools in the floodplains, a favorite mosquito breeding ground, later in the season than usual.

Hubert, the Yakima County manager, isn't so sure what caused the extra mosquitoes. He considers extra water only one of many theories.

Meanwhile, he agrees there were more adult mosquitoes, but oddly, he noticed fewer larvae in his water samples. He used only a fraction of his larvae control substance, a mixture of bacteria and corn cob granules. The granules dissolve and the larvae eat the bacteria, which then kills them.

To kill adults, control districts spray a fog of chrysanthemum flower oil at dusk and dawn. Hubert figures he will do that a record 25 nights this year.

The districts use an oil-based chemical spray, called surfactant, only as a last resort, they say.

The Yakima County district covers Union Gap, Moxee and Terrace Heights, but not the city of Yakima. Property owners in the district pay 18 cents per $1,000 of assessed value, or $18 per year for a $100,000 home.

The Benton County district, which includes Prosser and the portions of Yakima County around Grandview and Mabton, assess property owners 15 cents for every $1,000 of assessed value.

In the Lower Valley, horse owners say the mosquitoes have been bad, but nothing out of the ordinary.

"Certainly not any worse than usual," says Tim Foster, a cattle rancher in the Satus area, where an infected horse died this year.

The area saw high waters, but more farmers are switching from row irrigation to sprinklers or drip tape, leaving less standing water.

Joe Castillo, whose family has horses in the Grandview and Mabton areas, and Janay Murbach, a member of the Backcountry Horsemen, agree mosquitoes are just as bad this year as in the past.

But Lori Hyatt of Plymouth, an unincorporated community southeast of Prosser in the Horse Heaven Hills, has noticed a difference.

"We have a problem with them every year, but this year was worse than others," she says.

Hyatt lives near a pond just north of the Columbia River and claims she could hardly stand to work in her garden this summer. She complained to county commissioners, who now are talking to other property owners about forming a new mosquito control district.

"It's just not fun any more," she says.

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Information from: Yakima Herald-Republic, http://www.yakima-herald.com