September 22, 2020

The War Against Oak Wilt

Can we win before the forest loses?
By Patrick Sullivan | June 23, 2018

The infection probably hopped over from a neighbor’s woods, in the form of a beetle carrying a fungus and attracted to the sap seeping from a trunk damaged last summer. It left one red oak tree dead amid a forest of red oaks.

The tree’s death was confirmed this spring when buds failed to appear and bloom and the tree’s spindly silhouette became conspicuous amid a lush green canopy.

Mark and Trish Smith, who own the five-acre lot near the northeast corner of Benzie County where the tree had lived, knew they had to do something before the oak wilt fungus spread into the rest of their forest, which Mark Smith estimates is at least 80 percent red oak.

On a recent afternoon, Kama Ross, district forester for the Leelanau, Grand Traverse and Benzie Conservation Districts, stopped by to check out the infected tree and take a look at the oaks around it. The nearest four or five oaks probably share root systems with the dead tree. The closest of them could already be infected.

“It’s a super high chance that this is already infected, so it will likely show symptoms right around the Fourth of July,” Ross told the Smiths about a tree that’s five paces from their dead one. There are others almost as close heading off in other directions. And there are more within the root range of each of those trees. The Smith’s lot – with its one infected, dead tree – could be a case study in how oak wilt can spread exponentially once it takes hold.

“What if I didn’t do anything?” Mark Smith asked.

“It would just keep going, hopping from tree to tree, until it couldn’t find another,” Ross said.

That is essentially what’s happening at the Interlochen State Park, which Ross said is ground zero of oak wilt in the region, probably because campers arrived with infected firewood there some time years ago. It’s so bad around there and so many trees are dead or infected that Ross said she doesn’t usually bother visiting sites too close to the center because those trees are under assault from all sides.

She said her time is best spent consulting with landowners like the Smiths who are on the periphery of the outbreak and who have a good chance at blocking it from their woods.

Oak wilt is only one in a long line of threats to northern Michigan’s forest – along with the emerald ash borer and Dutch elm disease and a multitude of problems maple trees can face. Whatever’s up next may be just as bad or worse, whether it’s the hemlock woolly adelgid and the Asian long horned beetle.

With all of those stressors, Mark Smith said he is worried about what’s happening to the trees.

“It’s scary, because we do get oxygen from them,” he said.

Ross helps landowners manage their trees and she helps them figure out how to sell timber on their land.

That’s supposed to be the main part of her job, but more and more often, she said, she attends to people who have sick trees. It could be a full-time job. She focuses on helping people with oak wilt because its spread can be staunched, unlike some other tree diseases, which spread more freely. Answering oak wilt calls, however, takes up a lot of Ross’s time.

“I cover three counties. It’s a lot. I travel a lot,” she said.

Once it takes hold in an area, oak wilt tends to migrate by hopping from infected tree to a nearby uninfected tree through root systems that have become connected.

Oak wilt can strike trees in an unaffected area only when a tree is damaged during growing season, which allow picnic beetles to spread the fungus by giving them access to the inside of a trunk of an otherwise healthy tree.

You can stop oak wilt from spreading to a healthy, detached tree that’s been damaged by covering the area with latex paint, but you have to work fast. Ross used to tell people they needed to paint the damaged area within an hour so that the picnic beetles can’t find it. Oak wilt has become so prevalent in the region, Ross said, that she now tells people they need to paint the tree within 10 minutes to prevent an infected beetle from reaching its trunk.

Once a tree has been infected, there are ways to stop or slow the spread of oak wilt to nearby trees, and that’s why Ross drove all the way to Interlochen to consult with the Smiths.

She told them they should keep an eye on that nearby tree, but shouldn’t do anything until the fall. Then, they should quarantine the infected tree or trees by digging a trench around them that is five feet deep, enough to separate the root systems of the infected trees from the healthy ones.

Ross said she is seeing oak trees under peculiar stress this year and she isn’t yet sure what the explanation is, though she suspects stressors are intensifying because of climate change.

“Something else is going on,” Ross said. “It’s really early this year and it’s really confusing.”

Oak wilt is believed to come from Central America or Mexico because it first struck trees in the United States in Texas and moved north from there. It’s been in Michigan for decades but became more prevalent in the 1980s as people began to build houses in the woods.

Because of the way oak wilt spreads, by moving out in an ever-growing circle from an infected tree, oak wilt spread slowly and quietly at first, and then seemed like it picked up speed as it consumed vaster and vaster areas of forest so that it’s become the crisis that it is today.

Oak wilt spread accelerates as people move around and do things they shouldn’t do, like move firewood or prune oak trees in the summer.

“It’s because of the human connection and the lack of public knowledge about the issue,” said Annie Kruise, executive director of the Arboriculture Society of Michigan. “We, and when I sat ‘we,’ I mean, ‘we, as in the public,’ are taking firewood from certain counties and taking it to other counties and not knowing that that firewood is oak and it’s diseased.”

Kruise said she believe oak wilt can be managed if the public gets educated.

“We feel as professionals that we can manage this through education and awareness,” she said. “We feel that this is completely manageable.”

Remarkably, however, it’s not just regular people who need to be educated about the basics of oak wilt – don’t move firewood; don’t prune or damage oak trees during the growing season – people in the tree care industry often don’t know the basics, said Corey Parshall, who with his father owns Parshall Tree Care Experts.

“A lot of the problems, like oak wilt, get started by the tree companies who don’t know what they are doing,” he said. “A lot of tree companies don’t even know that still. I see tree companies pruning oaks throughout the summer and I just shake my head.”

Parshall said the tree care industry suffers from lack of education; it’s too often a business people get into buy accident, figuring they can make a few bucks with a ladder and a chainsaw.

“For too long, the industry has been outdated and it’s kind of been a ‘Chuck-with-a-truck’; a guy with a chainsaw,” Parshall said.

Parshall said that’s how he started nine years ago, opening the business with his father. They had a pickup truck and they were ready to work. The difference in Parshall’s case, however, is that since then, he’s been dedicated to educating himself and his employees about trees.

“We keep up on the science,” he said. “There’s a science to diagnosing insects and diseases. We want to see the industry itself become more professional.”

Parshall Tree Care Experts recently got approved through the Department of Labor to offer an arborist apprenticeship program. Parshall said he expects to hire and put through training two arborist per year through the program, which pays for education through Michigan State University.

Parshall lists lack of education among people in the tree care industry as one of the biggest threats to the region’s trees, right up there with oak wilt.

“A lot of the problems that I encounter is that homeowners are hiring tree companies without certified arborists or construction projects that don’t bring in arborists before groundbreaking,” Parshall said. “A lot of people neglect their trees. I get called in too late and I can’t save them.”

Erik Johnson discovered an outbreak of oak wilt that threatened his 20 acres of woods near Karlin in 2016 and he became determined to do something about it.

“I did a whole bunch of Googling and I found that there is a way that you can do it yourself,” Johnson said. “You can use a fungicide to inoculate your trees from oak wilt.”

Johnson discovered injectors that are manufactured to deliver chemicals into trees. He tried it out on the oaks surrounding the infected oaks on his property and he stopped oak wilt dead in its tracks.

“I used it all around my outbreaks and stopped the progression,” he said.

The treatment has to be repeated every one to two years, but Johnson discovered that by doing the treatments himself, he could save a lot of money. Tree service companies charge several hundred dollars per treatment, per tree.

Johnson knew that others would want to tackle oak wilt and other tree threats the same way and he became a distributor of Chemjet Tree Injectors and started a website and side business that he calls a hobby. By day, Johnson is an environmental engineer, so getting into the science of fighting tree disease as a hobby wasn’t too much of a stretch.

Anyway, Johnson said he understands how heartbreaking it can be to lose a beloved tree.

“This tree has been here for 200 years and then, bam, it dies. It’s just awful,” he said. “I am kind of on a crusade to save oak trees in my state, my town.”

On his website – – Johnson sells treatments for oak wilt, emerald ash borer, Dutch elm disease, pine bark beetle, hemlock woolly adelgid, and the Asian long horned beetle.

The treatments, though they have to be repeated, can stop the spread of a disease in a particular area because if, say, all of the oak in a section of woods are either dead or inoculated, there is no place left for the fungus to go, Johnson said.

“It’s really easy – you inject the tree and it stays alive,” he said.


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