If you look up in the sky this summer in eastern Baltimore County, you will see one of the world’s most expensive flyswatters.

The Model 206 L-3 is a black Bell helicopter, spraying a bacteria known as Bacillus thuringiensis israelensis (Bti) in meticulous rows over a 1,200-acre section of the Back River. The goal is to kill the millions upon millions of midge larvae so they do not grow up to annoy residents and destroy businesses in the marinas and waterfront homes in and around Essex.

So far, that effort has cost more than $3 million, with Baltimore County and the Maryland Department of Agriculture splitting the cost. And it’s not even halfway done.

So far, it’s working. Nearly two decades after residents first reported seeing large swarms of the tiny flies in the Back River area, the data show the numbers are well below the nuisance levels of 500 larvae per square meter. That’s a technical way of saying it’s safe to go outside, enjoy a cold beer, maybe even a cookout in one of the remaining affordable stretches of waterfront in the county.

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Kevin Brittingham, manager for Baltimore County’s Watershed Monitoring Program, dispenses a dredge sample from Back River in Essex on May 30, 2024. (Kylie Cooper/The Baltimore Banner)

Residents like Sam Weaver say the Model 206 is worth every penny. In 2007, the owner of Weaver’s Marine Service started keeping insecticides near all his doors. He vacuumed every time he opened one of them. It was never enough. The midge flies bred in the trees, so thick they’d weigh down the branches. Boat hulls turned grey from their swarms; siding turned brown from their excrement. Weaver, who had spent millions of dollars to rebuild his 120-slip marina following Tropical Storm Isabel in 2003, lost 60% of his business. Some of his relatives even left.

“You couldn’t walk on your pier. You’d have a face full of midges. You couldn’t tell what color your boat was,” he said.

Never mind enjoying a beer on your boat on a summer evening, added Councilman Todd Crandell, who represents the area and remembers the midge heyday well. “In order to go out on a pier at night, you would almost need to wear a beekeeper’s suit,” he said.

Kevin Brittingham, manager for Baltimore County’s Watershed Monitoring Program, explains how he uses an Ekman dredge to collect samples from Back River in Essex on May 30, 2024. (Kylie Cooper/The Baltimore Banner)

Midges occur naturally in the environment and are — in smaller numbers — a sign of a healthy waterway. A perfect storm of factors caused their explosion in Back River, according to Kevin Brittingham, the county’s manager for watershed monitoring.

Their favorite habitat is a low-oxygen, high-nitrogen, high-sediment mix. The Back River Wastewater Treatment Plant offered the high nitrogen and low oxygen as it treated the sewage of hundreds of thousands of residents. Nearby bridge construction brought sediment to a river already full of it, given that the Back River is shallow and flushes poorly.

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The plant had its share of problems that likely only helped the midges. The state and the nonprofit Blue Water Baltimore have sued Baltimore and its Department of Public Works for mismanagement at the plant, which discharged more bacteria, nitrogen and phosphorus than its permits allowed. For a time, the state took over management of the plant because conditions had deteriorated so much.

The lawsuit settled, with the city paying $4.75 million, and the plant reverted to city control.

Then came the commercial fishermen taking unlimited carp, which had feasted on midges. All of that, Brittingham said, threw the ecosystem out of balance.

Midges gather on a boat at Weaver’s Marina in Essex on May 30, 2024. (Kylie Cooper/The Baltimore Banner)

Like everyone else in Baltimore County, Brittingham wanted to get away from midges. He studied the flies and their larvae in his master’s and Ph.D. work. But maybe there is something about the devil you know. Using a tool called the Ekman dredge, Brittingham developed a protocol to count the midge larvae in the river sediment. The dredge grabs a sediment sample, and Brittingham washes off the dirt to count the larvae.

Each grab of the sample he multiplies by 43 to get the number of larvae in a metered square. He checks before and after a spray. After 12 sprays, he has figured out the right amount, when to spray it (not on windy days) and where to spray it. The Bti is a larvicide that does not harm humans or aquatic life or pollute the air. It only kills midge larvae.

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“It’s the way we do it in the bug world,” he said, adding that other cities with midge problems are calling to ask about his success and implement the protocol.

Essex, located about 8 miles east of downtown Baltimore, was not the first area to combat an infestation of the gnat-like insects; in the 1980s, the airport in Venice, Italy, had to divert flights because midges made the runway slippery and invaded engines.

Lake Victoria in Uganda has long struggled with what locals call “lake flies” that have taken a bite out of tourism. Several Florida cities, including Sanford, have been spraying for what locals call “blind mosquitoes” with a truck full of chemicals.

Kevin Brittingham, manager for Baltimore County’s Watershed Monitoring Program, sifts through a dredge sample from Back River in Essex on May 30, 2024. (Kylie Cooper/The Baltimore Banner)

But Baltimore County may have the distinction of the longest battle with the midges.

The first calls came in during the summer of 2007, according to Ellen Kobler, a senior advisor for communications with the Department of Environmental Protection and Sustainability. Politics stalled midge eradication efforts in 2016, when then-County Executive Kevin Kamenetz was contemplating a run for governor and then-Gov. Larry Hogan asked him to pay for half of the remediation. They didn’t resolve matters before Kamenetz died unexpectedly in 2018.

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Momentum picked up after Johnny Olszewski Jr, an east-sider, was elected county executive. Olszewski worked with Hogan’s agriculture secretary, Joe Bartenfelder, who had previously served on the County Council, to reach an agreement.

All told, the treatments will cost $7.5 million, split between the state and the county. In addition to the Back River itself, the county is treating the wastewater plant, where numbers are way down.

Spraying can’t continue indefinitely, but it also can’t stop. Getting nutrient pollution back in balance will help. So will regulating carp fishing to keep natural predators in the ecosystem, Brittingham says.

About 10 days after treatment, Brittingham pulled some wooden blocks out of standing water near a telephone pole —makeshift slides to test for midges. The flies are on the wood and hulls. Not so many that they overpower everything, but present, nonetheless.

Brittingham seemed pleased. “We never claimed we were going to kill them all.”

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A headline for this story has been updated to correct the river near where the spraying will occur. It is the Back River.