- Associated Press - Thursday, March 27, 2014

LARAMIE, Wyo. (AP) - Keith Wardlaw recalls Albany County before mosquito control. In the middle of summer, ranchers often wore down jackets and bandanas to work cattle.

Playing little league baseball in July, the most coveted position was behind home plate, Wardlaw said.

“As catcher, you could wear extra gear to keep mosquitoes from biting you, and you didn’t have to be out in the outfield in the grass,” said the city of Laramie Mosquito Control Crew supervisor. “They were that bad.”

This spring, Albany County and city of Laramie workers are preparing for an annual struggle that’s played out in the hay fields, river valleys and streets of Laramie since the 1970s.

On the one side, Albany County residents use science-based methods for surveying, targeting and killing mosquitoes.

On the other, mosquitoes have their inborn need to feed - that, and sheer numbers.

“Mosquitoes will go as far as they need to find a blood meal,” Wardlaw said. “That’s basically what it comes down to. And the city of Laramie is sitting here in the middle of this big, open basin. We turn all the lights on at night. And we have a lot of attractant features that potentially bring mosquitoes into town.”

The original Laramie Valley mosquito-control program began in the 1970s at the behest of ranchers, who found that fewer mosquitoes meant healthier cattle, Wardlaw said.

“(Before mosquito control), the calves spent more time running from mosquitoes, brushed up and not feeding, and the cows would brush up to find a place to get away from mosquitoes, and they weren’t taking care of their calves,” he said.

A calf born between February and March could weigh roughly 100 pounds more at the end of the fall season with mosquito control, Wardlaw said.

Since its inception, countywide mosquito control has expanded to encompass about 12 seasonal employees; dozens of volunteers; a city-wide program that includes pre-hatch control, aerial spraying and fogging trucks; three county mosquito-control districts and a town of Rock River mosquito-control district - all rolled up into an “integrated-management program,” Wardlaw said.

Through general fund money, Wyoming Department of Agriculture grants and match funding, Albany County - which includes city and county operations - will likely devote about $675,800 to mosquito control in 2014.

Mosquito control is important for nuisance, economic and health reasons, Wardlaw said.

Tourists are less likely to stay in areas where mosquitoes are excessively bothersome, he said.

Most importantly, Albany County is home to a species of mosquito - Culex tarsalis - that carries West Nile virus, Wardlaw said.

West Nile can transmit from mosquitoes to livestock and humans, potentially causing illness. In rare cases, the virus can cause death via brain inflammation, or encephalitis, according to the Center for Disease Control.

During the 2013 mosquito season, no human or veterinary cases of West Nile virus were reported within Albany County.

Three mosquito pools and one crow tested positive for West Nile virus infection, according to the city of Laramie website.

Mosquito control is partially responsible for the low incidence of West Nile in the county, Wardlaw said.

“One thing I can say for certain is that we have limited the population of (C. tarsalis) over the last 10 years,” he said.

Mosquito control is year-round, but it begins ramping up during the spring with larval control, Wardlaw said.

Larval control begins when water is warm enough to provide habitat.

That can be anywhere from early April to May, Wardlaw said.

Workers do dip counts to monitor mosquito numbers and lifestyle stages.

Just before larvae metamorphose into flying mosquitoes, workers apply soil bacteria called “Bacillus thuringiensis israelensis,” or Bti, to kill them, Wardlaw said.

The bacteria specifically targets mosquitoes and black flies. For that reason, about 90 percent of larval control in the county is through Bti application, he said.

“It’s a very easy way for us to treat those mosquitoes, and it’s very environmentally friendly,” Wardlaw said.

Early-season larval control doesn’t kill all of the county’s mosquitoes, of which there are 21 identified species.

Wardlaw said there are about five species that cause concern because of numbers or feeding preferences, including C. tarsalis, the West Nile vector.

Around peak season, typically mid-June to mid-July, aerial spraying begins targeting flying mosquitoes.

Chemical insecticides called Malathion and Dibrom are used for aerial treatments, according to a 2014 city of Laramie request for treatment proposals.

“In the county, most mosquito control is done through aerial spraying,” said Lindsay Wheat, Albany County Weed and Pest supervisor. “Most of it is along the river valleys, like Little Laramie, Big Laramie and Rock Creek river valleys. They’re targeting wet areas where mosquitoes likely hatch and hang out.”

Spraying also targets irrigated hay fields, Wardlaw said.

Although the insecticides are generally good at targeting mosquitoes, Wheat said the poison can harm honeybees.

Beekeepers are encouraged to register hives so they can be alerted when spraying goes underway, she said.

“Aerial spraying is pretty much targeted at air space above the water, rather than in the water,” Wheat said. “A little hits the water, but it’s not enough to kill fish.”

Wardlaw said the adult-control portion of the plan kicks in once traps show spikes in flying mosquito populations.

In addition, fogging trucks, which spray an insecticide called permethrin, begin applications in the city once the surveillance traps begin yielding high mosquito numbers, Wardlaw said.

Despite all of this, West Nile carriers can still persist, Wardlaw said. C. tarsalis’s life cycle lands late in the season, typically late June, July or later, he said.

The city began a more robust West Nile program in 2004, bolstered by grants from Wyoming Department of Agriculture.

The grants became available after West Nile became a bigger problem nationwide, Wheat said.

Additionally, the county continues its larvicide efforts through October to keep C. tarsalis counts as low as possible.

“Mosquito control is not just a truck rolling through the alley,” Wardlaw said. “This program is based on science. We use a whole host of scientific methods to determine what, when, where and how we do these things, and to make it as efficient, effective and environmentally friendly as we can.”


Information from: Laramie Boomerang, https://www.laramieboomerang.com

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