Tree-killing invasive species found in Benzie County at Sleeping Bear Dunes

Sheri McWhirter, The Record-Eagle, Traverse City, Mich.
·3 min read

Feb. 22—HONOR — A tiny, invasive insect recently detected in a national park campground set off a flurry of activity among environmental experts determined to fend off the threat as long as possible.

Evidence of hemlock woolly adelgid was found Feb. 4 on a tree in Platte River Campground within Sleeping Bear Dunes National Lakeshore. A sample taken was the following day confirmed as the invasive pest insect by the U.S. Department of Agriculture.

Now local and state invasive species experts want area residents to help them stay vigilant against HWA, which can kill hemlock trees within 10 years, weakening them by sucking the trees' sap out.

"This is our first infestation in our service area," said Audrey Menninga, invasive species specialist with Northwest Michigan Invasive Species Network. "We are pretty optimistic about it."

National lakeshore employees began surveying high-use areas within the park for HWA in January through Great Lakes Restoration Initiative funding. They found round, white ovisacs characteristic of the HWA on a single tree within the campground in Benzie County.

None of the other hemlocks in the immediate vicinity showed signs of the invasive insect in subsequent searches, officials said.

Menninga said evidence of HWA found late last year in Ludington State Park may provide a possible — even likely — pathway for its arrival in Benzie County. And she said evidence from the newest infestation shows the pest insect likely arrived in spring 2020, less than a year ago.

"We're pretty sure a camper brought it up with them," Menninga said.

The natural resources chief for the national park agreed with that educated guess.

"While human movement isn't the only way invasive species spread, it is the most common," said Julie Christian, SBD natural resource division manager.

While it's not ideal to find HWA in this corner of Lower Michigan, Menninga said it is fortunate this infestation was caught so early in the process.

"This is exactly why we do the surveys," she said, "so we can catch it when it's just the one tree."

State natural resources and agriculture officials said plans are in the works to treat the infected tree this coming spring, as well as all the surrounding hemlocks.

"While we never want to find a new infestation, discovering it early on, as in this case, when we have a reasonable chance of containing it and saving trees, is really the purpose of this program," said Rob Miller, an invasive species prevention and response specialist with the Michigan Department of Agriculture and Rural Development.

Those who live within five miles of Lake Michigan can have a free survey performed on their land to search for HWA, including those around Grand Traverse Bay. Further inland and the bugs are seemingly unable to survive cold winter temperatures, instead depending on the moderating effect of the big lake, Menninga said.

The Northwest Michigan ISN has already surveyed 388 acres since January, and agency officials want to continue to lengthen their to-do list. Plans are to continue surveying along M-22 near the new infestation, but Menninga said there are more places also worth inspecting across the agency's service area, including Benzie, Grand Traverse, Leelanau and Manistee counties.

Experts believe HWA can spread on the wind, hitchhiking on birds or mammals, or even by clinging on to vehicles, boats or recreational vehicles parked in close proximity. It's an invasive species that puts Michigan's estimated 170 million hemlock trees at risk, they argue.

Menninga said hemlocks provide an important temperature regulating effect in the region's ecosystem: providing food and shelter for deer and other animals seeking places to bed down and stay warm during frigid winter conditions, and cooling forest streams during warm summer months to maintain good habitat for cold-water fish.

HWA was first found in Michigan in 2006 and before this month, state officials said known infestations were limited to Allegan, Ottawa, Muskegon, Oceana and Mason counties.