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Not mosquito-free, but close: how 20 years of spraying has changed Sioux Falls

The sounds of late-night spraying familiar to city residents. West Nile Virus prompted the program and residents benefit from lower mosquito numbers. But recent heavy rains means a new wave is upon us.

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Sioux Falls mosquito-control truck.jpg
A mosquito-control truck used by the City of Sioux Falls Health Department. <br/>

SIOUX FALLS, S.D. — In the stillness of a summer night, the low drone of a mosquito spraying truck is a familiar sound in the leafy neighborhoods of the city.

Mounted in the back of white pickup truck, the sprayer spreads a mist of water containing a tiny amount of chemical that kills the bugs on contact as the cloud settles to the ground. The noise rises and falls like a cicada song as the truck moves from block to block.

It’s been part of Sioux Falls summers for 20 years, since the arrival of the West Nile virus in 2003, and it’s not going away anytime soon.

West Nile isn’t the headline-grabbing affliction that it once was. But it’s still here, with six human cases reported in South Dakota so far this year and 54 nationwide, including four deaths.

The South Dakota Department of Health estimates that there will be 88 cases by the end of the year. That's below the peak years when cases topped 150, most recently in 2018.


For Sioux Falls residents there is a merciful side benefit, which is the relative lack of mosquitoes during backyard barbecues, baseball games and bike rides.

It’s not that Sioux Falls is a mosquito-free zone, but until you spend an evening outdoors somewhere else, the dearth of the little buggers isn’t always top-of-mind.

Denise Patton.jpg
Denise Patton, entemologist and health program coordinator for the City of Sioux Falls

“If we could get rid of all the mosquitoes, we’d be cajillionaires,” said Denise Patton, an entomologist and health program coordinator for the City of Sioux Falls.

“It has become an expectation. People enjoy being able to go outside in the summer.”

The biggest misconception about the program is that it’s just spraying, said Patton. But that’s the last option, one that officials take as little as possible. Instead they continually collect data by monitoring mosquito traps, examining them under microscopes and mitigating potential breeding areas.

The chemical the city uses is a product called Aqua Reslin, which is approved by the Environmental Protection Agency for use in residential areas. Patton said there is less than a teaspoon of the product used per acre sprayed.

The chemical breaks down very quickly when it hits the ground. It’s safe for humans and animals so there’s no need to seek shelter when a truck comes through your neighborhood.

“Honestly it’s not going to hurt you,” said Patton. “I’d have a third arm by now if that was the case.”


Sioux Falls isn’t the only community doing mosquito control in South Dakota. The Department of Health administers $500,000 in grants to prevent West Nile. Nearly 200 cities, counties and tribes received grants this year ranging from $500 to $20,000.

The city also helps out neighboring communities, covering about one-third of the state’s population.

a close up view of a culex tarsalis mosquito perching on a human hand
South Dakota health officials estimate there will be 88 cases of West Nile Virus in the state in 2022. The mosquito species Culex tarsalis is responsible for transmitting the virus to humans.
Contributed / Centers for Disease Control and Prevention

The amount of spraying is highly dependent on the weather, specifically how much rain we get.

That’s why Patton expects another mosquito wave soon because of a five-inch deluge that hit recently. That’s when awareness about West Nile also peaks.
“People panic and think, ‘I’m going to get West Nile,’” she said.

The good news is that the mosquitoes that hatch after the big rains, while probably the most annoying and noticeable because they are “hard” biters, aren’t the ones that carry West Nile.

There are 43 different species of mosquitoes living in South Dakota. The ones that carry the virus thrive in drier conditions, and their bite isn’t as noticeable.
That said — and not to overstate it — the only good mosquito is a dead mosquito.

“We just don’t want them,” said Patton. “The end.”

Find out more about mosquito spraying

Mosquito control spraying in Sioux Falls is done by zones. Residents can find out what zone they are in and when spraying is scheduled on the city’s website at www.siouxfalls.org/spray or get notifications via text message. Just text the word SPRAY to 888-777 to receive the notifications.


To report concerns about mosquitoes or standing water, leave this information on the automated Mosquito Reporting Hotline at 605-367-8799.

Related Topics: SIOUX FALLS
Patrick Lalley is the engagement editor and reporter for the Forum News Service in Sioux Falls. Reach him at plalley@forumcomm.com.
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