Mosquitoes in the Boundary Waters

I haven’t noticed more mosquitos in the Boundary Waters this year but evidently there are more than normal in the metro area.


Metro mosquitoes triple 10-year norm

by Sasha Aslanian, Minnesota Public Radio

ST. PAUL, Minn. — No doubt about it, the mosquitoes are bad this year after a very wet spring.

But exactly how bad are they?

Every week, the Metropolitan Mosquito Control District sets traps and counts them. In the lab where scientists empty the traps, it seems the tables are turned on the mosquitoes.

Instead of swarming outside the mesh on tents, or dive-bombing people for a blood-meal, the mosquitoes are trapped in little mesh bags — so many mosquitoes that the bags pulsate.

“What you’re seeing in there is pretty much all mosquitoes,” Mosquito Control entomologist Sandy Brogren said.

This week, the mosquito population is three-times as high as the 10-year average. The prize for the biggest specimen bag goes to Eagan, Minn. It’s one of 134 traps set across the metro area.

The mosquitoes are headed for the freezer to die. Mosquito Control will tally up the various species and test for disease.

Staffers peers through microscopes at petri dishes and poke tiny forceps through what first appears to be thick brown moss. But on closer examination, the moss is really piles of mosquito bodies.

“I’d say once I finish, there’s going to be about 400,” staffer Alex Johnson says, sorting his sample from Maplewood. “So, pretty decent amount and this was just from our front yard.”

Mosquito Control staffers collect samples from their own yards in addition to the traps that are hung throughout the metro. Mosquito Control mostly tries to nip mosquitoes in the larval stage, but counting adults helps determine where to deploy more resources.

On a map, Brogren points out the many different mosquito populations across the metro.

“As you can see, there are a lot that are above threshold right now,” Brogren said.

The rainy cold spring meant spring and summer species of mosquitoes arrived right on top of each other, giving us a big burst in mid-June. Each additional inch of rain means more mosquitoes hatch when rainwater finds their eggs. Right now, Minnesota is getting the “cattail mosquito,” a particularly aggressive strain that hatches in cattail swamps and usually peaks around July 4.

Of the 51 mosquito species in Minnesota, Mosquito Control focuses on the ones that bite people, and the ones that carry disease.

Culex Tarsalis, the mosquito the carries West Nile, likes prairies such as those in Carver and Scott counties in the southwestern metro. Those areas get a lot of monitoring.

Other mosquitoes are just annoying, Brogren said, and staff have given them less scientific names.

“There’s one species we call the ‘insidious ankle-biter,'” she says, laughing. “Because they tend to really like your ankles.”

Brogren is a 40-year veteran of Mosquito Control. She says she loves her job and there’s always more to learn about mosquitoes. In its 55-year history, Mosquito Control has changed the chemicals it has used as it seeks to find methods that are safer and better for the environment, Brogren said. The district now uses a soil bacteria and a hormone that inhibits growth.

In the metro area, a homeowner with a house valued at $250,000 pays about $13 a year for mosquito control. But outside the seven-county metro area, Minnesotans brave the mosquitoes unassisted.

If Mosquito Control is successful, people won’t get bitten as much at popular summer gatherings. The State Fair is a priority, Brogren said.

“All summer long we kind of keep an eye on that, so that the populations don’t get so out of control that we can’t get it down to a level that’s comfortable,” Brogren said. I’ve never been bit by a mosquito at the State Fair so I think we’re doing a good job there.”

To prevent bites and mosquitoes from spreading, Brogren advises people to:
• Wear long sleeves when doing an outside activity, such as gardening.
• Spray clothing with a product that contains DEET.
• Cover rain barrels with a screen to prevent mosquitoes from laying eggs there, and dump anything that holds water in your back yard. Change birdbaths once a week.

Editor’s note: Further analysis by Mosquito Control concludes that mosquito levels are greater than earlier reported. This story has been updated to reflect the latest analysis.