The buzz on mosquitoes

Conditions have been perfect recently for a last gasp of mosquito infestation. Experts tell why it’s happening.

MARSHALL -- Don't put the insect repellent away just yet because even as summer is starting to wind down, many people in the area are seeing an uptick in the mosquito population.

The pesky insects appear to be flourishing as a result of abundant rain in the area in mid-August.

"The mosquitoes are pretty vicious right now," said Bruce Potter, integrated pest management specialist for Lamberton's Southwest Research and Outreach Center. "It's the worst it's been this summer. It's most likely a result of the rains we got a couple of weeks ago."

Marshall Mayor Bob Byrnes, who also serves as director of field operations for the University of Minnesota Extension, agrees with Potter's hypothesis.

"The conditions are ideal right now," Byrnes said. "We went through a period of time where we had cool, damp weather and then followed by warm weather. It allowed the hatch to take place and the mosquitoes to thrive."

Jeff Hahn, an entomologist with the University of Minnesota Extension, said it is not typical to see an influx of mosquitoes in the middle of September.

"We see them late spring and early summer typically," Hahn said. "That's when they start to come out. Sometimes it depends on rainfall."

Hahn added that mosquitoes are less active when the conditions are dry or cool.

"Generally, when we get dry times, it reduces the mosquitoes we see," he said. "When it's cool, they will usually be less active. When it's warm out, they can still be active."

Oftentimes, frequent or heavy rains can cause water to pool on the ground, creating a perfect habitat for mosquitoes to lay eggs. Hahn said there's always a lag time between the rains and the presence of mosquitoes.

"The eggs have to hatch and the larvae needs to develop and become active," Hahn said. "It depends on the species and the temperatures, but it takes at least a week or more."

Minnesota is home to more than 50 mosquito species. Not all of them feed on humans, though.

"Of the ones that are around here, it's just the females that are biting," Potter said. "The males feed on nectar."

Some area residents have been directing concerns about the nuisance via Facebook posts to the city of Marshall. One woman said her family cannot even go outside to enjoy an evening because the mosquitoes are so bad. She then references a friend who has to spray her kids before they wait to get on the bus in the morning.

Another woman said she's afraid to take her daughter to the park because of the bad reactions she gets from mosquito bites.

According to Byrnes, the city of Marshall discontinued the practice of spraying for mosquitoes on a city-wide scale more than 25 years ago.

"The city of Marshall does not have a spray program," he said. "It does for special events, depending on the need and what the population of mosquitoes is. They do spray the parks for special events, but they don't go up and down the street spraying like some communities do."

Byrnes noted two reasons why Marshall no longer sprays for the pest.

"There were concerns about the use of the insecticide and secondly, there were complaints that cars on the street had some residue because of the spray," Byrnes said. "So we discontinued the practice here in Marshall more than 25 years ago. The hope is that, as with everything, it's a temporary problem."

Hahn said the Metropolitan Mosquito Control District, a government agency that was started by the Minnesota Legislature in 1958, helps control the mosquito population for 2.7 million people living in the Twin Cities area, covering 2,900 square miles.

"They cover a seven-county area by applying an insecticide in the form of a solid mass that gets put into the water to affect the immature mosquitoes," he said.

Hahn added that the MMCD primarily identifies small lakes, ponds and other wetlands to use as a host for controlling the spread of the pest. The larval surveillance and control season starts in February and runs through October. It takes roughly 180 seasonal inspectors to handle the work. In the off-season, there are 53 full-time employees.

According to the MMCD website, the two larvicides they use -- Bti and methoprene -- pose no danger to humans, pets or wildlife, even if they drink the water. The site added that killing mosquitoes does not deprive wildlife, such as ducks and bats, of their food because they do not rely on a single source.

"It's not common around here, but they've got some pretty aggressive treatment for larvae in the cities," Potter said.

Spraying for adult mosquitoes using pyrethroids poses no measurable health risk to humans or animals, the website said, but the insecticide is toxic to fish and bees, which is why they try to avoid spraying near water or blooming crops.

Unfortunately, mosquitoes can also reproduce and thrive in stagnant water in the most random of places.

"They can certainly breed in other areas," Hahn said. "It doesn't have to be associated with the rain. They can use artificial containers, like swimming pools, bird baths or rain barrels if they're not covered properly. We're always telling people to drain containers. Don't let them fill up and sit around because that would be a breeding area for mosquitoes."

Hahn added that catch basins where water runs down the street gutters could also provide an ideal breeding environment.

"There has to be water for the larvae to mature," he said. "Larvae needs standing water and it has to have organic materials for it to feed on."

The MMCD website also revealed that closely spaced rains -- much like parts of southwest Minnesota saw in mid-August -- can often produce more than one brood of mosquitoes in the water at the same time.

"They can breed in any shallow water, including rain barrels, buckets and even a dog dish outside," Potter said. "It doesn't a lot of water."

Despite being limited in how much adult mosquito spraying the agency can do, the MMCD reports that most residents in the seven-county metro area consistently enjoy about a 75 percent reduction in mosquito levels thanks to their efforts. But it isn't without a cost. Property owners pay for it through special taxing. In 2016, a property assessed at $250,000, for example, is charged about $14.00 for mosquito control.

While reducing annoyance and improving the outdoor conditions are important, the MMCD is also focused on reducing the risk of mosquito-borne diseases -- La Crosse encephalitis, western equine encephalitis, eastern equine encephalitis, West Nile virus and dog heartworm are all present in Minnesota.

Last year, two Balaton men contracted West Nile, which was detected in the state for the first time in 2002. According to the Centers for Disease Control (CDC), there were 148 human cases of the West Nile virus in Minnesota -- four that resulted in death. In 2004, there were 34 human cases and no deaths.

Of the 2,374 confirmed cases of West Nile reported to the CDC in 2013, 79 Minnesotans were affected -- three of them fatally.

"The good news is that the species around here aren't the ones that can carry malaria," Potter said. "It's also good news that it's been dry, so it's helping keep the puddles down. That will limit the next generation. But if we get a shot of rain, all of that can change again."

Experts suggest reducing the risk of infection by limiting their exposure to mosquito bites -- not always an easy thing to do in Minnesota in the summertime. The top tips include wearing a bug repellent that contains DEET, wearing light-colored clothing and avoiding the outdoors during peak mosquito hours -- at dawn and dusk -- as much as possible.

"It really comes down to personal protection," Hahn said. "It can be difficult to do vicinity control for mosquitoes, so it helps if people wear protective clothes and repellent."

Facebook posts from the city of Marshall have been assuring area residents that the Parks Department is actively looking into the mosquito situation for the community.

"Trust us, we're just as annoyed with these little buggers as much as everyone else in our wonderful community," the post said.

If nothing else, people can hope for an early frost.

"We usually get the first frost in October," Potter said. "Once we get a hard frost, the mosquitoes will disappear."