So you think mosquitoes are a pain? How 'bout those gnats?

After a brutal winter and near-record spring floods, Minnesotans now are enduring waves of biting "buffalo gnats" that seem impervious to the usual repellents.

"I would say it's approaching historic levels," said John Walz, coordinator of black fly control with the Metropolitan Mosquito Control District.

Minnesota has 15 varieties of black flies, which most people call gnats. Four have an appetite for human flesh, including simuliida meridionale, the one Walz says is "hammering us right now."

Buffalo gnats, which have a hump on their back, are known as bird biters, but they're just as happy to munch on people. They don't spread disease to humans, but Walz said children who suffer many bites can develop a fever.

Kim Husband is a freelance editor who likes to work on her deck in Bloomington at this time of year. Usually, she will apply bug spray once in the morning and once in the afternoon. But this year, she said, even Deep Woods formula Off is failing to hold the gnashing gnats at bay. She has tried a homemade repellent made from mouthwash and Epsom salt and finally resorted to wrapping a bandanna around her face — something she's never had to do before.

"I'm feeling defeated," Husband said. "I hate losing outdoor time on a gorgeous day, but I can't work when I'm waving my hands in front of my face."

Gary Wyatt, an agroforestry educator with the University of Minnesota Extension service, said he was struck by the swarm of black flies that coated a greenhouse he visited recently in New Ulm. Locals were asking for lemon grass or lemon basil as a possible natural repellent, as well as Bug Soother, a repellent made by a family-owned business in Columbus Junction, Iowa. The spray contains water, lemon grass oil, lemon, vanillin, castor oil, glycerin and vitamin E. The company says people like the smell, which recalls vanilla ice cream, but the bugs hate it.

Ordinarily, the Metropolitan Mosquito Control District would have treated the black fly larvae on the Minnesota and Mississippi rivers in early May with a naturally occurring bacteria found in the soil. But floodwaters this year prevented that, so the first generation of black flies has matured into adults and has taken to the skies in search of a blood meal.

The district doesn't treat adult black flies, which survive two to three weeks. The biting gnats, which lay their eggs around moving water, typically have four to six generations a season.

"It's been a pretty ugly year so far," Walz acknowledged. "They're pretty bad right now and I know it, but I can't do anything about it."

Walz, president of the North American Black Fly Association, said the Mosquito Control District will begin treating the larvae as soon as the rivers return to their normal channels. The No. 1 target is the Minnesota River, which has seven treatment sites, he said. Walz said he expects to exhaust the annual $100,000 budget for treating black flies this year and will need to find other money to finish the job.

Minnesotans love to hate their mosquitoes, which some jokingly call the state bird. But black flies can be more annoying, Walz said. Mosquitoes, which also are starting to emerge, puncture the skin and siphon out a meal. Black flies use their scalpel-like proboscis to slice the skin, injecting it with anticoagulants and painkillers so they can sup from a pond of blood on the skin.

Is there's an upside to the black fly swarm?

"It is good for fish," Walz said.

Dan Browning • 612-673-4493