State foresters are trying to get a better handle on a disease that’s taking out mature red oak trees across the state. “Oak wilt” can spread quickly. An outbreak nearly shut down one of the most popular state parks in Michigan this year.
A Decision No One Wants
Loggers took more than 800 dead or diseased trees out of Interlochen State Park this past winter, including nearly every red oak in the park.
“You hate to see this type of operation in a state park,” says Dave Lemmien, the forest supervisor for the Grand Traverse Area. “But if you had to have it…”
Lemmien says it was either that or close the campground because there were so many large standing dead trees that it was a hazard to campers.
He says people who come back to the park this year will definitely see a difference, but he thinks when they learn the reason they’ll agree with the decision.
“I think the public outcry of closing down the oldest state park in the state would far outweigh cutting down trees,” he says.
Lemmien says not all of them had oak wilt. Many were dead and dying from close to a hundred years of use and abuse and from other stresses, such as drought and forest tent caterpillars.
Spread By Beetles
Red oaks are a dominant tree species in the Interlochen area that produce food for deer, wild turkey and squirrels. Luckily white oak species are mostly immune to oak wilt. Diseased trees develop a fungus beneath the bark. A type of flying beetle then is attracted to the smell put out by the fungus.
“A lot of folks think it has an odor reminiscent of juicy fruit gum or fermenting wine,” says Roger Mech, a forest disease specialist for the DNR.
Red oaks that are pruned or damaged during the warm weather also attract the beetles to their sap, and that’s how the spores of the fungus are spread to healthy trees.
With an early spring warm-up this year the beetles are flying earlier than usual and a tree that’s been infected dies within a few weeks.
“It’s mid-summer and you’re standing there and the leaves are coming down on that red oak tree like it’s fall, it’s a pretty safe bet that’s it’s oak wilt,” Mech says.
Hard To Spot Early
The kicker is that oak wilt also spreads underground as well. The roots of red oaks graft together and share water and nutrients. They also spread the disease more slowly that way and that’s why when DNR does aerial surveys it’s hard to pick the beginnings of an infestation when there’s only a few trees with dead crowns.
Bob Heyd, a forest pest manager for the DNR, says the disease has been detected in more than forty counties and the state doesn’t really know how much of the forest is affected. He says oak wilt can be especially devastating in cottage communities where people may do a lot of pruning or cutting down trees in the early summer.
“Where you’ve got a pretty dense canopy of oak trees that produce a lot of values. Not just wildlife but aesthetic values, shade,” he says. “And they bring oak wilt in and they don’t know what’s going on and they start cutting trees out. And if we don’t pick up on this I’ve seen landscapes along lakes just cleared of their oak.”
Firewood Can Spread
Cutting down newly dead trees for firewood and moving it is another way oak wilt is spread. Forest manager Dave Lemmien says it’s going to take everyone partnering up to get the disease under control.
“Because if somebody decides to prune their oak trees during the summer or bring up firewood from an infected tree, the cycle is never going to end,” he says.
Crews at Interlochen State Park are still cleaning up debris from the logging operation, but the park supervisor expects all the campgrounds to be open by Memorial Day weekend.