For the past several years, mosquito-control crews have used small planes to spray pesticides over vast stretches of wetlands west of Salt Lake City International Airport.

The waters flowing off the mountains are impounded year-round in stagnant ponds and braided stream channels, creating ideal breeding habitat for the pesky blood suckers that spread disease and annoy people.

The cost runs into hundreds of thousands of dollars a year, but officials have come across an outfit that will do the job for free: the U.S. Air Force.

The military is happy to perform the spraying as a way to train pilots as they fine-tune their skills for flying close to the ground.

If all goes as planned, the Air Force will deploy a C-130, a large four-engine turboprop transport aircraft, in September to wage chemical warfare on the swarms of mosquito species that proliferate there, according to an environmental assessment prepared by the Salt Lake City Mosquito Abatement District.

“We’re really saving the taxpayers a lot of money,” said Ary Faraji, the district’s executive director. “These are applications that we would be conducting regardless. But instead of the citizens of Salt Lake City paying for that, we’re having the Air Force come in and make these applications for us.”

(Trent Nelson | The Salt Lake Tribune) Ary Faraji, executive director, at the Salt Lake City Mosquito Abatement District’s facility on Thursday, Feb. 25, 2021.

The district is accepting public comment through March before rendering a decision. Whether the project is approved, the district will continue aerial spraying with small planes using private contractors who charge about $2,000 an acre.

But some environmental and duck-hunting groups are raising doubts about the wisdom of applying chemical poisons over critical bird habitat just upwind from Utah’s main human population center.

“There are just studies and studies about the neurotoxicity of these pesticides, including the ones they intend to use with this program,” warned Brian Moench, president of Utah Physicians for a Healthy Environment. “They’re not just theoretical concerns. These include epidemiological studies showing that people who live closer to where these chemicals are used have higher rates of problems, specifically loss of cognition on the part of children.”

He had been unaware the mosquito district conducted aerial spraying before the environmental assessment released last month. His group is working to put an end to it, regardless of whether the Air Force project is approved.

Aerial spraying makes up 10% of the district’s operations, Faraji said. The majority of its work entails targeted treatments of standing water inside the city, using larva-eating fish and chemical larvicides applied directly to the water.

“Every aspect of our operations is dictated by science, by data, by facts,” said Faraji, who holds a doctorate in entomology. “We take in the overall ecology and biology of the species that we’re dealing with. We look at efficacy data. We evaluate different formulations for use. We really go out of our way to ensure that we’re mitigating our environmental impact and our ecological footprint out there.”

What insecticide will be used and where?

(Christopher Cherrington | The Salt Lake Tribune)

The treatment area covers 43,000 mostly uninhabited acres west and north of the international airport. Much of this region is privately owned and used for agriculture and duck hunting. It also includes the Gillmor Audubon Sanctuary, a bird preserve on the Great Salt Lake’s south shore, and the sites of the new state prison and the proposed inland port.

While Faraji understands Moench’s concerns, he believes they are misplaced because the district applies the pesticides in extremely low concentrations and in ways that minimize risks to human communities and other nontargeted creatures, such as birds and pollinating insects.

“I got into this game because I love wildlife. I’m passionate about insects,” he said. “And if there’s anything that I can do to preserve the environment and the flora and fauna that we deal with, we’ll go out of our way to ensure that.”

To kill adult mosquitoes, the district uses an organophosphate insecticide called Dibrom, applying less than a fluid ounce per acre, far below what the Environmental Protection Agency has deemed safe, Faraji explained. Agricultural applications, by contract, use gallons of this product per acre.

For aerial spraying, planes are equipped with a high-pressure applicator that atomizes the product into billions of tiny droplets, 50 microns across, or less than the diameter of a human hair. The droplets are released at altitudes of about 100 feet, sometimes as high as 300 feet to avoid bird and power lines.

“When they get down to about the ground level, where the mosquitoes are, the droplets are in the 10- to 15-micron size. They are super, super small,” Faraji said. “Our intent is to have just one droplet be enough to impinge on a mosquito and cause a toxic effect. But if that same droplet is going to land on a beetle or a moth, a much larger insect, it’s not going to have the same toxic effect.”

By spraying only after sunset, the applications avoid pollinators and other beneficial insects, which are typically inactive at night. No spraying occurs if wind speeds exceed 10 mph.

Currently, the district employs private contractors who fly twin-engine Piper Aztecs or Chieftains.

“That’s a very expensive process for us,” Faraji said. “If I’m conducting a 15,000-acre application, I’m looking at about a 30 grand cost. I cannot possibly do that every week during the course of the season. I’ll blow through my budget in a heartbeat.”

Health threats from mosquitoes

(Trent Nelson | The Salt Lake Tribune) Assistant director Greg White holds a vial of mosquito specimens ready for testing at the Salt Lake City Mosquito Abatement District’s facility on Thursday, Feb. 25, 2021.

The district already expects to see its costs rise when it increases applications to protect the new state prison under construction in the area. Faraji emphasized, however, that the Air Force project has nothing to do with either the prison project or the planned inland port.

The C-130 to be used is based at the Youngstown Air Reserve Station in Ohio as part of the 910th Airlift Wing. This unit already deploys to Utah once or twice a year to apply herbicides needed to knock back invasive cheatgrass on the military’s 1.7 million-acre Utah Test and Training Range in the West Desert.

Faraji’s staff selects the areas to spray with the help of a network of 30 mosquito traps, which are checked twice weekly throughout mosquito season. A trap can yield up to 20,000 mosquitoes in a single night, although about 300 can be enough to trigger a treatment.

The retrieved traps are brought to the district’s new facility at 2215 N. 2200 West, where the mosquitoes are killed in a freezer, then counted, sorted by species and analyzed for the presence of pathogens. District microbiologists are looking for three disease-causing viruses: Western equine encephalitis, St. Louis encephalitis and West Nile.

Mosquitoes that feed on birds and mammals are the ones most likely to transmit disease.

Having appeared in Utah in 2003, West Nile virus commands the most attention. To date, this virus has infected 422 people in the state, according to the environmental assessment. In most cases, the infected person does not even feel sick, but in one of 150 instances, the patient develops a serious illness, according to the federal Centers for Disease Control and Prevention.

Moench noted two Utah cases were reported last year.

“They take a distorted view of the public health threat of West Nile virus,” he said, “to the point where they’re really making the ‘cure’ worse than the disease.”

The physicians group says it is preparing a scientifically supported rebuttal to the district’s proposal that will not only highlight the environmental and public health risks of spraying, but also warn that it can worsen the mosquito problem by promoting resistance.

“There are some studies to suggest that, in fact, the insects that survive rebuild their populations very quickly, so they develop resistance to it,” Moench said. “But the insects that survive are actually more heavily contaminated with the pathogen that causes West Nile virus and they have higher bite rates.”

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