Beech Bark Disease Spreads in Door County

Whitefish Dunes State Park naturalist Carolyn Rock points out the white fuzz that’s a telltale sign of Beech Bark Disease. Photo by Carol Thompson.

The forest Carolyn Rock sees when she stops at a group of beech trees along County Highway WD has changed since last spring.

“When you look at the forest, last year you don’t remember seeing so many white trees,” Rock, Whitefish Dunes State Park naturalist, said. “Now you see them everywhere.”

The trees are covered with white fuzz, a telltale sign of Beech Bark Disease. It isn’t obvious at first, but once someone points out the wooly coating on the smooth beech bark the evidence is spread throughout the forest near the park entrance.

The fuzz isn’t really the problem – it just signals that a tree is infested with beech scale, or tiny, invasive insects that suck sap out of American beech trees. The insects don’t do all the damage on their own, but leave the trees stressed and susceptible to fungi that kill parts of the wood and stop the trees’ flow of water and nutrients.

Eventually, after they’re hit with the bugs and the fungi, the trees become weak or die.

Beech scale insects are easy to detect; they make the white fuzzy material on beech trees. The fungi are harder to find, and forester Chris Plzak said although they haven’t actually been detected in Door County they’re definitely here. He knows because trees are already dying.

“We have beech trees that are dying of beech bark disease but we haven’t actually found the fungi,” Plzak said. “Our insect pathologist said it is here we just haven’t found a confirmation of it.”

The European Beech scale were introduced to Nova Scotia in 1890, then spread to the East Coast of the United States in the 1930s before eventually reaching Door County in 2009. The bugs move by sailing along air currents, or through firewood.

“If you’re driving down the road with a truck full of infested logs, these little scale insects could blow off and get launched into the wind and then act like a kite and fly around for a while, and then potentially land on a beech in this area,” said Linda Williams, Department of Natural Resources forest health specialist.

Williams and Plzak don’t know exactly how beech scale got here, but they know that since their introduction the bugs have spread from Washington Island to Southern Door. Most of the county’s beech trees are holding up for now, but trees in the area where the disease was discovered haven’t been so lucky.

“That’s what we call ground zero, the first spot we saw [beech bark disease] in August of 2009 behind Glidden Drive,” Plzak said. “We’ve had a lot of beech mortality in that area.”

The rest of the trees won’t hold up forever. Plzak expects Beech Bark Disease will kill more than 95 percent of Door County’s beech trees in the next 10 to 15 years.

That turns out to be a lot of trees. The U.S. Forest Service estimates there are 2.1 million beech trees in the county, and if only the standard two to five percent are resistant to Beech bark disease, we could be left with just 60,000 to 100,000 in 2028.

As the disease sweeps through the county’s forests, the damage will first be evident in Whitefish Dunes. But, as Rock said, it’s not all bad. The dead trees will attract animals such as woodpeckers, and as the logs decompose they’ll create more soil. Then, when the disease-resistant beech trees start to repopulate, local forests will be even healthier.

Besides, beech trees aren’t the only ones there. The forest at Whitefish Dunes is diverse, so even after most beeches die other trees will remain.

“Keeping diversity of the forest is important so when we don’t have such a stark disturbance to fight off, and the forest will be healthier too,” Rock said. “It’s the way it’s supposed to be. We’ll survive.”

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How to Prevent Beech Bark Disease From Spreading

Don’t transport beech (as commercial wood or firewood) between July 15 and November 15, because that’s when the insects are mobile and could spread.

Don’t remove beech before beech bark disease is found in the stand because some trees may be resistant.

Report resistant trees to the Department of Natural Resources.

Ornamental or high-value trees can be protected with an insecticide, or by scrubbing bark with a soft brush or strong stream of water to kill the scales.

Source: Wisconsin Department of Natural Resources Best Management Practices for Reducing the Movement of the Beech Scale.