These Minnesotans serve as mosquito bait so you don’t have to

Skaters do figure-eights on ice, but Kylie Rich-Vetsch does them in air — with a butterfly net.

Each week, she joins the Monday Night Sweep Network, a crew of employees and volunteers from the Metropolitan Mosquito Control District (MMCD), as part of a metrowide fight against the bloodsuckers.

Like others in the network, she goes out in her yard or neighborhood park at dusk on Mondays, about 45 minutes after sunset, when mosquitoes are most active.

Rich-Vetsch remains still for 1 minute to let the mosquitoes be drawn to the carbon dioxide she exhales. Then, for 2 minutes, she sweeps the net in front of her body and overhead in elegant loops, switching arms when one gets tired.

It’s “best to be short-sleeved and have some exposed skin so the mosquitoes have a way to get at you,” said Scott Grant, a field supervisor with the MMCD.

Rich-Vetsch stores the mosquitoes she collects in a special box in her freezer overnight, then brings them to work the next day for the entomologists to study.

“People call us heroes,” she said, “and that is very touching to me.”

But Rich-Vetsch does more than act as a mosquito magnet. As a seasonal field technician, she’s one of an army of MMCD employees whose job it is to “dig around swamps all day” and find spots that need mosquito control.

“We have a couple hundred employees. They go to where the mosquitoes are at their absolute worst to make the summer a bit more enjoyable for everyone else,” said Kirk Johnson, the MMCD’s vector ecologist.

The sweep net is one of the district’s three surveillance mechanisms, which include light traps and gravid traps (tubs of smelly water representing a “highly organic aquatic habitat” that’s attractive to egg-laying mosquitoes).

“We don’t use these traps to reduce mosquito populations; they really don’t catch enough mosquitoes to impact the population at all,” said Johnson. “The traps are just a surveillance mechanism to measure the population.”

Entomologists in the MMCD’s lab process the mosquitoes coming in weekly from the sweep and the traps, identify the species and then update the staff database. That information is used to determine “areas where additional work may be needed to reduce isolated populations of target species,” Johnson said.

Minnesota is home to about 50 species of mosquitoes.

“Aedes is the genus of the mosquitoes that we probably spend most of our money and resources trying to target,” said Grant. Gravid traps tend to collect mosquitoes of the Culex genus, responsible for West Nile virus. By managing mosquitoes like these, the MMCD can reduce disease transmission.

Helicopter treatment, which targets mosquito larvae, is the method the district relies on most because it can treat up to 10,000 acres in a single day. The MMCD applies methoprene pellets, which have a “juvenile hormone mimic” that disrupts larvae’s metamorphosis, and Bti, which is a group of naturally occurring soil bacteria that attacks the larvae’s stomach walls.

“Their guts kind of explode,” Grant said.

The team also fights the adult mosquito population on the ground by spraying permethrin, “a synthetic analog of pyrethrins, which are a natural insecticide produced by chrysanthemums,” Johnson said.

Once mosquitoes land on a plant that’s been sprayed, “the material gets absorbed into their nervous system,” Grant said.

The district works hard to “minimize non-target impacts,” Johnson said.

When employees are spraying on foot or by an all-terrain vehicle in daytime, they are trained to stay away from flowering plants and milkweed, where bees or butterflies may be present. The MMCD also engages with local honeybee groups, which document the location of hives, which the district avoids. At night, ultra-low-volume fogging may be done in specific areas when mosquito numbers are especially high.

This year, there’s been record flooding in parts of Minnesota, according to the National Weather Service. Coming on the heels of several years of drought, that means many of the state’s wetlands “just banked several years’ worth of mosquito eggs,” which hatched simultaneously, Johnson said.

That the Twin Cities has over 80,000 wetlands means we’ve got a lot of mosquitoes.

MMCD employees are doing what they can. And some, like Rich-Vetsch, are even enjoying it. “I actually love digging around swamps all day,” she said.

Residents can do their part, too. Mosquitoes may dwell in wheelbarrows, tarped areas, buckets, wagons or tires — spots where water collects. “We have little cute sayings like ‘When in doubt, dump it out.’ Some people don’t realize they’re bringing mosquitoes into their yards by just the stuff they have lying around,” Grant said.

So, if you’re outside some evening, slapping skeeters, just remember: You’re not on your own.

“Know we’re out there,” Rich-Vetsch said, “fightin’ the good fight.”