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Black flies may be extra pesky this year

Published 9:52am Monday, June 30, 2014

MINNEAPOLIS — Black flies are such annoying biters that most people would rather be bitten by a mosquito. Unfortunately, the pesky pests are about to appear throughout the state in large numbers.

The recent rains and flooding have left parts of the state awash in high, running water — ideal breeding conditions for the bugs also known as biting gnats or buffalo gnats. Compounding the problem is the fact that typical eradication efforts aren’t as effective this year.

That could mean plenty of annoying swarms this summer.

They’re not just annoying, though. Whereas mosquitoes bite with pinpoint finesse, black flies have “slashing mouth parts” that rip off a piece of skin to give them access to blood, said Jeff Hahn, an entomologist with University of Minnesota Extension. That leads to more discomfort than a mosquito bite does.

Agencies including the Metropolitan Mosquito Control District fight black flies by pouring bacteria into rivers to kill the pests. But there’s so much water this year that the bacteria are being diluted into uselessness, agency spokesman Mike McLean said.

“The amount we’d need (to be effective) is so great, we’d blow the whole budget in one treatment,” McLean said.

That means the black-fly population could explode this year. It’s already happened in northern Minnesota, where swarms were so thick that some loons abandoned their nests to flee the blankets of bugs, leaving their eggs exposed to heat, cold and predators.

“They get in (the birds’) eyes and nasal passages, they can’t breathe,” said Lori Naumann, a spokeswoman for the state Department of Natural Resources.

It’s too early to say how many loon chicks died, but DNR officials note that the birds can lay a second round of eggs in a season.

As floodwaters recede, the black-fly problem should ease up. However, if the water becomes stagnant, it can lead to fresh problems with mosquitoes, McLean said.

“In a month or so, if we have this much standing water, we’re going to look closely at what’s coming out of it,” he said.