Damage from ash borer likely to reshape Marinette County Forest

NORTHEAST WIS. – Dead ash trees are coming down in Marinette County by the dozen and threatening to reshape the landscape.

The cost to municipalities from emerald ash borer damage often is tens of thousands of dollars in removal expenses per year — not to mention lost shade until other tree species take the ash trees’ place.

Emerald ash borer sightings are expected to crop up this spring and summer as the half-inch-long shiny green insects emerge and gnaw on the inner bark of ash trees. The insects leave behind exit holes as a telltale sign they were there, said Pete Villas, owner and consulting forester at Villas Forestry Consulting LLC in Peshtigo.

Dead branches, flaking bark and woodpeckers feeding on larvae beneath the bark often follow, Villas said.

“The sad part is that once these signs are present, it’s too late and the tree will die within the next couple of years,” said Villas.

Ryan Bourassa, forestry administrator for Marinette County, is predicting 90% to 100% mortality of the county forest’s ash trees over the next five to 10 years. Only outliers and the smallest saplings might have a chance of survival, he said.

“The land base is being reshaped by this infestation. There’s very little a landowner can do to stop it,” he said. “There’s no combatting it.”

Villas shared his insight, “The damage is at or nearing its peak. At some point, there won’t be enough ash trees to support the beetle population.”

Bourassa explained that for now, treating the ash borer is just not economically feasible in Marinette County.

At 230,000 acres, the Marinette County Forest is the second largest county forest in the state. Its timber sales generate about $1.5 million per year on average for the county’s operating budget, while supplying about 60,000 cords of wood for forest industries, according to the county website.

The low-lying areas ash prefer, particularly near the bay of Green Bay, pose a challenge to tree removal.

“We don’t have equipment to go into areas that are rotting,” Bourassa said.
Ash trees on private property near power lines, homes or other buildings should be removed to prevent greater damage.

“If people have them around their houses, they are at risk of having those trees fall on their house. Ash becomes very brittle very quickly,” Bourassa explained.
Villas also shared his advice, “Winter is a good time to remove a dead or dying ash tree because the signs of emerald ash borer will show up earlier in the year and the beetles are not active.” Villas said.

To tell if a tree is infected, look for yellow leaves in the spring and new branches sprouting out of the trunk in the summer. D-shaped exit holes and pieces of bark on the ground below the branches indicate the borer has damaged the tree and moved on, Villas said.

If a tree with borer damage is on city or village property, contact the municipality for assistance. In most areas, trees on private property are the property owner’s responsibility.

With the borer spreading quickly from tree to tree, “Any species of ash is designated for removal,” Bourassa said.

He added that the county is currently “allowing the [ash] stands to naturally convert so we’re not putting a burden on the taxpayers.”

When the ash dies, water rises in the stands because the dead trees aren’t taking up water, he said. Over time, new species are expected to take root, such as hard maple and basswood.

When the emerald ash borer first took hold in Wisconsin, a quarantine was imposed to prevent the borer’s spread. But the borer infestations have spread quickly across the state.

Marinette County and other areas along the bay and lake are among the most affected areas because of the food available to the ash borer.

“It only hosts on ash trees, and the trees do well in low-lying areas with poorly drained muck soils,” he said.

To avoid possible damage from falling branches, municipal workers are busy removing trees and arranging for contractors to take down large trees and those located near power lines or other obstacles, increasing the hazard involved with their removal.

In Menominee, Mich., the county board in February approved contracts for the removal of ash trees at Kleinke Park, especially those located near power lines and other obstacles making their removal more risky. About 35 to 40 trees on county property will be cut down and their stumps removed, county administrator Jason Carviou said.

In Oconto Falls, nearly all of the 73 ash trees identified in the city’s tree inventory showed signs of damage from the ash borer, according to Eocene’s 2025 report. The city has removed over 35 trees since the inventory was taken last year, including 25 high-priority ash trees damaged by an emerald ash borer infestation, street superintendent Wally Remic said.

“The insect is already established in our area, and stopping its spread is no longer feasible. The most effective management strategy is the removal of affected trees,” Remic said.

While the Eocene report estimated removal costs at about $450 per tree, the city uses its own personnel to remove trees and the cost is cut in half, Remic added.

Tree size and the hazard level involved with cutting it down determine the cost.
After trees are removed, the wood is ground into chips and turned into mulch for parks and playgrounds. City residents also can pick up the mulch at the city’s recycling center, Remic said.

To prevent transmission through firewood, Villas recommended residents remove cut trees, split and stack the ash wood and let it dry out before moving it.

“Dead branches typically are too small to be used by the beetles,” he said.
“Because of this, they can be disposed of by simply piling them up, keeping [them for use] as firewood.”