Beech Bark Disease On Eco-Invader List

By John Flesher
SENEY NATIONAL WILDLIFE REFUGE, MI – Tracy Casselman runs a hand over the smooth, gray bark of an American beech, noting the scratch marks left by Black Bears that have clambered up the tree to munch nuts rich in fat and protein.

“Take a good look,” says Casselman, manager of the Seney National Wildlife Refuge. “In five years, these trees won‘t be here.”

Scientists expect the disease eventually will kill most of the state‘s beeches, changing the environment in ways as yet uncertain. For example, it could affect populations of bears and smaller mammals that feed on beech nuts — and that hunters enjoy pursuing.

Beech bark disease has been overshadowed by the Emerald Ash Borer, a murderous insect wreaking havoc on trees in southeastern Michigan and creeping steadily northward.

“When I was in college, I could name maybe half a dozen exotics,” Casselman says. “Now I could spend 10 minutes rattling them off. I just wonder when people are going to recognize the cost of bringing all these exotics in.”

Debate continues over preventing new invasions through measures such as limits on ballast water dumping by foreign ships in Great Lakes ports. Tighter controls on ornamental plant imports would be helpful, says Michael Lusk, invasive species coordinator for the U.S. Fish and Wildlife Service, who inspected stricken beech trees at Seney last fall.

Beech bark disease slipped into North America in 1890, courtesy of ornamental trees shipped from Europe to Nova Scotia. Over the next century and more, it moved across eastern Canada and south to New England, New York, Pennsylvania and West Virginia. Spot infestations have turned up even farther away, including Ohio.

Once established, beech bark disease can be spread by the wind, birds and animals that brush against infected trees.

Beech bark disease actually happens in two stages.The scale injures the beeches, making them vulnerable to a fungus called nectria that kills tissue and often entire trees.

Heavy winds sometimes cause “beech snap,” in which weakened trunks break in half. To protect hikers, authorities removed more than 200 beeches along trails at Tahquamenon Falls State Park, says Deborah McCullough, forest entomology professor at Michigan State University.

“As far as trying to slow (the disease) or contain it, not much can be done,” McCullough says. DNR forest managers are thinning large beech stands in hopes of impeding its progress.

One hopeful sign: For unknown reasons, some beech are proving resistant to the disease. Scientists are studying them in hopes of developing hardier strains that could be planted to rejuvenate the species, Heyd says.

Beech are not the most prevalent of Michigan hardwoods. They‘re found most often within areas classified as maple-beech-birch, which make up about 7.2 million acres of the state‘s 20 million acres of forestland, Heyd says. In such areas, maple and birch tend to outnumber beech.

As a timber product, beech wood is used primarily for niche items such as bowls, says Tom Barnes, executive director of the Michigan Association of Timbermen. It sometimes turns up in furniture and flooring and is prized as firewood.

But its ecological value is considerable. Cavities in the older trees provide habitat for birds, Fishers and Pine Martens. Hawks and eagles perch on their stout limbs. Triangle-shaped beech nuts are a crucial nutrient for many birds and mammals, including squirrels, deer, foxes, Ruffed Grouse, ducks, turkeys, Blue Jays and warblers.

There‘s no readily available substitute for beech nuts as a food source in the 95,238-acre Seney wildlife refuge, a patchwork of woods, fields and wetlands teeming with waterfowl. Managers acknowledge they don‘t know how the loss of most or all beech trees would affect the refuge‘s animal populations.

“Bears are omnivores, so I don‘t expect a big impact on them,” staff forester Greg Corace says, gazing at a snapped-off beech in an area infested with the invasive scale. “But some species may be less adaptable. We just don‘t know what will happen, but we suspect it isn‘t going to be good.” –AP