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Officials battling beech disease

Posted on October 10, 2013

Newberry, Mich. — A disease is spreading throughout northern Michigan, one for which scientists have no cure. But that doesn’t mean they hold no hope.

The disease results from an infestation caused by an exotic insect and a couple of fungi. And the insect, beech scale, is “exotic” only to the degree that it is not native. It has been present in North America

since 1890 when it was accidentally introduced into Nova Scotia. Its long-established presence has caused an equally longstanding problem: beech bark disease.

Dr. Robert L. Heyd, forest health specialist for the Michigan DNR, explains the progression of the disease.

“BBD results from a two-step process. First, beech scales will attach themselves to a tree, bore into the trunk and branches, and feed on the sap. These insects secrete a white, waxy substance, so an infected tree will look as if it’s covered in a thin veil of wool or cotton. The wounds caused by the beech scale allow one of two species of the Neonectria fungus to enter the tree where it kills the woody tissue. Once the damage to the mature trees is completed, the insect and fungi will infect saplings, then seedlings.”

In Michigan, BBD is a relatively recent concern, but it’s spreading exponentially.

“Beech scale was first discovered in Michigan in campgrounds in Luce County in Upper Michigan and Mason County in northwest Lower Michigan in 2000,” James B. Wieferich wrote in the 2013 thesis for his master of science degree at Michigan State University. “By 2003, beech scale had been detected in five counties in eastern Upper Michigan and four counties in west-central Lower Michigan.”

According to a map supplied by Heyd, as of May 2013 BBD now infests 30 Michigan counties, including eight that extend from the eastern U.P. to the southern borders of Marquette County and 22 more that cover roughly the northwest portion of the Lower Peninsula. According to the DNR paper, 2012 Forest Health Highlights, “Newly infested areas in the Lower Peninsula are being reported every year.”

Confirming those numbers in “Progression and Impact of Beech Bark Disease in Michigan,” part of that same DNR paper, Wieferich and Dr. Deborah McCullough report, “In 2003, beech scale was present in only 23 of the 62” plots they had set up to study the disease, including 14 sites in the U.P. and nine in the Lower Peninsula. Beech scale is now present in 55 of the 62 sites.

During the past five years, the disease has spread at an extremely variable rate, Wieferich and McCullough say, from 1 to 6 kilometers (approximately .6 to 3.6 miles) per year.

It is difficult to detect every instance of BBD in an area. For example, Heyd said one way the beech scale is spread is by birds. So the upper level of a tree might be covered in the white wax and because of leaf cover, foresters wouldn’t be able to detect it. So, to play it safe, if they find one infested tree in an area then the entire area is considered infested. And once the disease takes hold, the tree will die.

Heyd said, “The scientific community has found no way to stop the natural spread of beech bark disease or to control the disease once it arrives.

“The disease will not go in reverse. If we want the species here, we have to be proactive.”

Scientific proactivity has produced a “one and done” scenario for the disease, though Heyd says, “It’s going to be a while to get it up and running.”

The DNR reports that since 2002 it has been working with the Northern Research Station of the U.S. Department of Agriculture-Forest Service to select and breed American beech trees for resistance to BBD.

Says Heyd, “We already have at least 20 resistant families of (beech) trees we can replant. Beech scale can’t establish itself on them. This is one of the most hopeful exotic problems we have.

“We will slowly repopulate” the areas of diseased trees with the disease-resistant trees, he said. The added bonus: the BBD-resistant strains will produce resistant seeds.

Heyd noted that the resistant strains are being developed in Brighton and on the Michigan State University campus.

“That’s our plan. We’re going to repopulate Michigan’s forests with American beech as a viable component.”