Published on 07/08/98

Biting Blackflies Bring Summer Misery

Just when Southerners thought they'd seen the last of El Ni¤o's effects, in come the biting blackflies.bfly1.GIF 
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"Blackflies are interesting pests," said Ray Noblet, head of the entomology department of the University of Georgia College of Agricultural and Environmental Sciences. "There are lots of misconceptions about them."

Typically, blackflies aren't as prevalent in the South as they are in the Northeast or Northwest. But thanks to the El Ni¤o-induced wet weather this winter and spring, they're here in force.

"We've had an outbreak of blackflies where we haven't had them in years," Noblet said.

El Ni¤o can't take all the blame, he said. Give credit to better water quality, too. Blackflies can't breed in polluted water.

"Streams that didn't have blackflies because of pollution problems 20 years ago have been cleaned up," Noblet said. "Now they breed readily, and you see large populations of blackflies."

Blackflies aren't like mosquitos, which breed in standing pools of water.

"The water has to be flowing for blackflies to live in it," Noblet said. "You will find them anywhere adjacent to rivers and streams. You can see them around ponds where there is a stream leading from the pond or an active spill way."bflyvert.gif (12105 bytes)

The small, dark, stout-bodied flies are about half the size of mosquitos and are often mistaken for gnats. But they aren't.

"They swarm around your head," Noblet said. "But they're bigger than the eye gnat Southerners typically have to deal with. They're pretty hard to identify without a microscope."

You can, however, tell a blackfly by its bite.

"They have biting mouthparts much like a deerfly or horsefly," Noblet said. "They cut a hole in your skin and suck the blood that pools after they make a wound."


Those in south Georgia who thought living below the gnat line was bad enough now have a new worry.

"We're seeing them down there this year," Noblet said. "We've even had calls from Florida. Early in the summer they had high numbers in the Tampa Bay area, where we've never heard of them even talked about before."

Getting rid of them is a problem, too. By the time you see the flies, it's probably too late to control them.

"A successful control program must be directed at the larval stage," Noblet said. "And it has to be started in advance. The main thing you try to do is interrupt the breeding at the larval stage. It's hard to kill the adults. You can fog like you do for mosquitos, but they'll just fly in again."

A new biocontrol agent is now on the market.

"It's a new bacterium or Bt (Bacillus thuringiensis var. israelensis) like those used to control a lot of insects. But this one is specifically for flies and mosquitos. It works great," Noblet said.

"It's not a chemical pesticide, so it doesn't pollute streams or damage water quality," he said. "But you have to cover a wide area, because they will fly three, four or five miles."

The biocontrol is more for golf courses or horse camps that need to cover a large area. It won't work well for your own backyard.

This summer's dry weather may prove to have the best solution for the blackfly problem.

"Populations will begin to tail off fast now," Noblet said. "By late July to early August, we should see things improve. The dry weather will help. A lot of the streams breeding them now will dry up by then."

Faith Peppers is the director of public affairs with the University of Georgia College of Agricultural and Environmental Sciences.