Voracious biting black flies hatched in rain-swollen creeks and rivers are on a feeding frenzy in some Twin Cities neighborhoods, sending some victims covered with itchy red welts out of their yards and others into doctors’ offices in search of relief.
Meanwhile, recent rain combined with warm weather likely will be a boon to Minnesota ticks, which have been infecting more people with Lyme disease as they expand their territory throughout the state. About one in every three adult blacklegged ticks (also known as deer ticks) carry the bacteria that transmits Lyme disease, as do one in five nymphs, which are about the size of a pinhead, said Dave Neitzel, a vectorborne disease epidemiologist at the Minnesota Department of Health.
As the ticks peak in June, other bugs will follow: mosquitoes that buzz and bite, flies that circle and chomp and swarms of midges that you inhale on evening walks.
“It’s the price we pay for nice weather,” said Jeff Hahn, University of Minnesota extension entomologist.
In the Twin Cities, the Metropolitan Mosquito Control District is attempting to keep the mosquito and black fly populations at tolerable levels.
To keep biting gnats in check, the district adds a liquid bacterial product to kill the larvae in streams and rivers.
But because of high water in rivers and creeks this year, the district has treated just 80 percent of what it usually does to diminish the black fly population, said district spokesman Mike McLean.
“When streams overflow, it’s useless to treat it because the [treatment] doesn’t end up in the channel. It ends up in the backwaters, and then you’re not really controlling anything,” he said. “There are going to be some spots in the metro area where people are going to notice some intense black fly populations.”
While the district has treated the South Fork of the Crow River in the southwest metro and several spots on the Minnesota River, it hasn’t treated Minnehaha Creek, where some residents are scratching black fly welts. “We encourage people who are getting bitten up to give us a call,” McLean said.
Master gardener Julie Nelson, who lives about a quarter-mile from Minnehaha Creek, may do just that.
Last year, when repeated rain kept rivers and creeks flowing, the black fly population burgeoned in Nelson’s southwest Minneapolis neighborhood. “I got my first bite last year in June and the last one in November,” she said. “It literally drove me out of my garden.”
Nelson would gladly trade black flies for mosquitoes, which are bigger and more likely to be repelled by DEET and other repellents. “These little gnats seem not to be affected by anything,” she said. “You don’t know when they’re biting. They get caught in my curly hair. They leave welts that hurt, scar and last for 10 days. I’ve been gardening for 20 years and I’m beside myself.”
Her neighbor, Elaine Olson, said two of her three children have become black fly targets, leaving them with itchy, swollen welts that take about two weeks to disappear. “I called the pediatrician who said they’re getting lots of calls, but there’s not much to do but dab on hydrocortisone cream,” she said.
Hahn, the U entomologist, said he’s gotten a few more complaints this year about black flies.
He acknowledged they are a nuisance, but said they at least don’t transmit diseases like some mosquitoes and ticks do.
In Minnesota, the number of Lyme disease cases has been rising since the mid-1990s, jumping dramatically in the early 2000s, said Neitzel of the state Health Department. In 2015, 1,176 cases of Lyme disease were reported to the agency, compared with 252 in 1996.
“Except for the southwest third of Minnesota, most of Minnesota is considered to be moderate or high risk for tick-borne disease,” he said. “The tick is becoming more established in most of the wooded areas in the state. Along with that, we’ve had no trouble finding ticks carrying disease.”
Besides Lyme’s, ticks can carry other diseases such as anaplasmosis, babesiosis and the Powassan virus. Since 2008, 22 cases of the Powassan virus have been reported. “It’s rare but it’s potentially serious,” Neitzel said.
Health officials also have received anecdotal reports of people developing meat allergies after being bitten by a tick. “We don’t really have good evidence of how often it occurs or what’s going on,” Neitzel said.
This year, adult blacklegged ticks began coming out in February after an early snow melt, and Neitzel expects a “fairly high number of ticks” will be out in the next few weeks. “I don’t know if it’s going to be worse than normal, but now is the time for people to protect themselves,” he said.
Mosquito-slapping also will begin soon.
Provided the Twin Cities doesn’t get inundated with rain through the summer, the Metropolitan Mosquito Control District is “confident” its treatments have cut the mosquito population.
Still, there will be plenty of other bugs to swat.
Biting deer and horse flies will circle your head, “getting into your hair, biting your face, ears and your arms, of course,” Hahn said. “They’ll chase you and find you.” And don’t forget about the stable flies that look like house flies except that they bite, he said.
It’s unlikely that anyone will encounter all these bugs at the same time, Hahn said.
“I don’t want people to freak out,” he said. “It’s just something you take in stride because winter is way too long to shutter ourselves up.”