Death of an American giant: Hemlocks falling victim to Asian insect infestation (NC)

The Idaho Statesman
September 18, 2008
By Bruce Hendersen

The country's tallest eastern hemlock, reaching to the sky from a cove of Great Smoky Mountains National Park, towers 173.1 feet from its 5-foot-thick base to its last pencil-thin sprig.

The tree is 400 years old, armored in rough bark, and dead.

Millions of hemlocks across the Southern Appalachians are dying, victims of an Asian insect that has moved faster than efforts to stop it. The trees' collapse will change these forests, from warbler nesting habits to the temperature of trout streams, unlike anything since the 1930s. That's when a foreign fungus finished off another keystone tree, the chestnut.

Will Blozan and his fellow big-tree lovers call the record hemlock Usis. It's the Cherokee word for antlers and refers to the massive geometry of limbs in the tree's crown.

For nearly three years, Blozan, an arborist from Black Mountain, has led a project to find, document and save the biggest trees infested by the hemlock woolly adelgid. The tiny insect attaches to the base of hemlock needles and sucks the life out of the trees in as little as three years.

Nowhere do hemlocks grow bigger, or fall harder, than in Cataloochee, on the North Carolina side of the Smokies park, 30 miles west of Asheville.

"We're finding them right as we lose them," Blozan says. All 15 of the tallest eastern hemlocks are already dead.

In February 2007, when his team first climbed it, Usis was in deep decline but still bearing green needles. Twice the team injected insecticide into the soil around it. But the chemical needs water to work and drought wrung the mountains dry last year. By October the great tree was dead.

Last month they climbed Usis again, this time to map its architecture for posterity.

High in the tree, strapped into his ropes, Blozan can already hear insects called hemlock borers gnawing into dead wood. Their holes make it look like shotgun pellets have riddled the tree. Woodpeckers will follow, knocking off bark in search of larvae.

Limb by limb, over four days, Blozan and his business partners, Brian Hinshaw and Jason Childs, measure heights, lengths, diameters, forks and angles. Blozan fills a yellow notebook with penciled numbers. Someday they will be fed into a computer program to produce a finely detailed, rotating digital image.

It will be all that's left of a hemlock that stood from the time of Cherokee warriors to the European settlers who cleared farmland on the valley floor.

"From the top of the tree you just see gray, gray, gray," Blozan says. "I know this forest really well. I've climbed a lot of these trees. I witnessed this grove when it was alive, and now I'm witnessing it while it's dying.

"You can see for miles, and everywhere you look it's just death."

The adelgid hitched a ride to the East Coast more than a half-century ago, it's believed, on a shipment of nursery stock from Japan. First seen in Richmond, Va., in 1951, it moved north up the spine of the Appalachians, probably by clinging to migrating birds that nest in hemlocks.

Frigid Northeastern winters slowed the Asian insect there. But the South doesn't have that advantage, and the adelgid spread toward North Carolina - slowly at first, then in a surge.

By 1993, Virginia's Shenandoah National Park was overrun - 95 percent of its hemlocks are now dead. By 2001, the adelgid was in the high country of Western North Carolina, the heart of the hemlock range. Wind quickly spread it from tree to tree.

North Carolina foresters had experienced a similar attacker decades earlier and never gotten rid of it. A European insect called the balsam woolly adelgid attacks the Fraser and balsam firs that stand on the state's highest peaks.

If you've been to Mount Mitchell, the tallest peak in the Eastern United States, you've seen the standing skeletons of dead firs. The balsam adelgid infests only mature trees, killing them within a few years. That's why the only living trees on Mitchell's 6,684-foot summit are young ones.

Two key differences make the hemlock adelgid an even worse invader. It attacks hemlocks young and old. And while firs cover only about 75,000 high-elevation acres in the Southern Appalachians, hemlocks number in the millions.

"We know full well there are too many hemlocks to try to save," says Rusty Rhea, a U.S. Forest Service entomologist in Asheville who's leading the agency's adelgid fight. "We don't have a lot of tools here. We're still trying to figure this adelgid out."

The Great Smokies serve as both laboratory and graveyard.

Park officials, aware of the Shenandoah devastation, knew it was only a matter of time before the adelgid invaded the Smokies. Hemlocks dominate 35,000 of the park's 521,000 acres.

The white, waxy "wool" the insect wraps itself in was spotted in 2002.

The Smokies park has battled non-native invaders virtually all of its 68 years. "When you drive through the park and don't see kudzu, it's no accident," Kristine Johnson, the park's supervisory forester, says of one successful battle.

Still, more than 50 exotic plant species have found a foothold. Foreign pests and diseases have already attacked dogwood, butternut, beech and mountain ash trees, in addition to firs.

From the park's overlooks, the ashen gray of dead, barren hemlocks is impossible to miss in the sea of green.

"This is the first year of seeing trees that we knew were definitely dead," Johnson says. "The drought last year put them over the edge."

She guesses that 20 percent of the park's hemlocks may be dead and has little hope for most of the rest.

Given the adelgid's rapid spread and the lack of knowledge on how to control it, Rhea adds, "If I could save a third of the (hemlock) range or more I would be happy."

Blozan insists that more could have been done to save the trees.

With the Shenandoah hemlocks already infested, he says, the government spent too much time before attacking the Smokies adelgids with chemicals. His own company has invested $100,000 in labor and expenses, supplemented with $25,000 from the park, to try to save the trees.

"With the chestnut there was no choice - people watched them die and there were no tools to save them," he says, sprawled beside Usis. "But that's not the case with hemlocks. We have the ability to save a piece of our ecological history that we're losing."

In Tennessee and Kentucky, where hemlock stands are still healthy, Blozan is helping prepare government agencies for what will come their way.

Rhea, the Forest Service official, said the problem isn't easily solved. Money - the Forest Service spends up to $4 million a year fighting the adelgid - has to be found. Chemical treatments have to be tested.

"We have to find a middle ground there," he says. "We're being aggressive and we're trying to be fiscally responsible, and I think we've done that.

"I'm passionate, too. I've dedicated 15 years of my life to try to make this go away."

In Nellie Cove, where Usis stands, pileated woodpeckers chisel the bark off dead trees, leaving long red scars in the gnarly trunks. Streams run amber after heavy rains, stained by the tannins in the bark.

Some hemlocks have already fallen, their trunks splintered like toothpicks. Sunlight floods north-facing slopes that had been cool, wet and dark for centuries. Pokeweed rises among the rhododendron.

That's just the beginning, Johnson says.

"When the hemlock forests start to collapse in the next year or two, the difference in the watersheds will be dramatic," she says. "It's going to be millions of trees falling across the streams."

The trees will block creeks and trails. Dozens of species of birds will lose food and nesting places. Without the temperature-stabilizing microclimates that hemlocks create, trout streams will be colder in winter and warmer in summer. The deep, spongy forest floor will dry.

"It's going to be," Johnson says, "a very different place."

TOOLS IN THE ADELGID FIGHT

Government agencies are using three tactics in trying to slow the adelgid's advance.

Chemicals

The Smokies park sprays insecticidal soaps on infested hemlocks or injects insecticides to be taken up by roots. The treatments are laborious, expensive at about $16 a tree, and must be repeated about every three years.

Some 75,000 park trees have been treated, in high-visibility areas such as campgrounds and the 33 "conservation areas" that preserve a sampling of hemlock habitats and genetic diversity.

But chemicals are only a stop-gap fix.

Predators

The long-term plan is to stock the forests with insects that prey on the adelgids and hope the hemlocks themselves, in time, will fight back.

Dozens of insects feed on adelgids in their native Japan and China, and two predatory beetle species have been released in the Smokies. Success is likely to require several kinds of bugs, and years to establish them. Researchers have to be sure that the mercenaries won't cause unintended ecological damage.

Genetics

An international conservation program of North Carolina State University's forestry school is preparing for the worst.

The Camcore program collects hemlock seeds and grows trees in places the adelgid hasn't reached - Arkansas, Brazil and Chile. It also looks for trees that might be bred into an adelgid-resistant race of hemlocks.

"It's really the last-ditch effort," says director Bill Dvorak. "If all else fails, we want to make sure we have genetic material in a location that would allow us to re-establish this species."

The problem is that the trees are dying faster than seed-bearing cones can be collected. "One year we see a stand," Dvorak says, "and then we go back and it's gone."

NOTICE: In accordance with Title 17 U.S.C. Section 107, this material is distributed without profit to those who have expressed a prior interest in receiving this information for research and educational purposes.

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