The invasive mile-a-minute weed has been confirmed in Jackson County after previously being found in only one Michigan county.
According to Michigan’s Department of Resources, the new infestation lies only two miles from the closest known site in Calhoun County, but made it across county lines.
Katie Grzesiak, an invasive species coordinator with the Michigan Department of Natural Resources, said they are unsure of exactly how the weed spread to the new area, but it’s likely due to human activities or birds.
“The best thing about invasive species prevention is that you actually don’t have to know anything about invasive species to do it,” she said. “It’s important before you leave a site after you’ve been hiking or working outdoors that you’re cleaning your shoes, any supplies or vehicles.”
The weed is on Michigan’s invasive species watch list because of its ability to grow six inches within a single day, she said.
“It’s not yet really widely distributed, but it is so good at growing and so good at impacting our ecosystems and agriculture that it’s a problem,” Grzesiak said.
The species is native to Asia and grows the fastest in wet areas with plentiful sunlight. The weed overtakes crops, shrubs, and trees to get as much sunlight as possible but smothers all other plants in the process, she said.
The mile-a-minute weed is an herbaceous vine with several key features that make identification easier. It has slim stems and completely triangular leaves with straight sides and sharp points on the underside.
“We have lots of vines in Michigan, but most of them don't have these prickles or if they do, they’re like straight prickles but these are more like the thorns on a rose where they're kind of curved,” Grzesiak said.
The weeds also grow berries, which can be a pale green or pinky-purple as they develop but ultimately become a bright blue.
The Barry, Calhoun, Kalamazoo Cooperative Invasive Species Management Area released thousands of weevils into Calhoun Country as a biological control method to manage the weed earlier this summer.
“We anticipate that those weevils will not eradicate mile-a-minute weed but we're hoping that they're a tool in the toolbox that can help us manage mile-a-minute weed,” she said.
She said if you do see the weed, it is possible to hand pull them but usually herbicides are necessary.
“Often once it gets going, herbicides are the best way forward because there's just so much plant,” she said. “It's really hard to control in any other way and it's much too aggressive to just let it go.”
Two Cooperative Invasive Species Management Area groups from six Michigan counties are working together to monitor and manage the weed; their work is funded through Michigan’s Invasive Species Grant Program, Grzesiak said.
The groups surveyed around 3,000 acres in Jackson County and 2,600 in Calhoun County but found no further infestations.
Grzesiak said if residents come across what they think to be a mile-a-minute weed, they should take a photo to help with identification and use the Midwest Invasive Species Information Network online reporting tool. This tool was used in the identification of the infestation in Jackson County.
