published Monday, December 7th, 2009

Daunting threat to save timber

Audio clip

Jonathan Evans

The hemlock woolly adelgid has spread into Southeast Tennessee and North Georgia and foresters fear the worst: the possible loss of some of the Cumberland Plateau region's most graceful evergreen trees, eastern and Canadian hemlocks.

Walden on Signal Mountain already has a large and growing infestation. The parasite also has been found on Lookout Mountain.

In North Georgia, the bug that sucks the life from hemlocks has moved through the Blue Ridge area eastward into Fannin, Murray and Gilmer counties. The Asian invader has no natural predators here.

"When it gets headed to the valley, it will be really hard to contain," said John Thomason, an arborist with ABC Tree Service.

In Walden, Chattanooga attorney Lee Davis hired ABC Tree Service to save the ancient hemlocks on the historic Topside property he owns in the Summertown neighborhood.

"I've been studying up on these bugs for about three years," Mr. Davis said, noting that his two-story log home, built in 1883, wouldn't have the same feel without the massive hemlocks that likely are as old as the house.

PDF: Adelgid paper USDA

PDF: GA Adelgid SoilInjection

PDF: USDA 2008 spread map wooly adelgid

SPOTTING ADELGIDS

* Look for cottonlike puffs at the base of needles.

* Turn the branch over and look for tiny black dots about the size of pepper specks.

Source: John Thomason, ABC Tree Service

"One thing I found out is that the cost of treating the trees is nothing compared to the cost of having them cut down if they die. We're talking hundreds (of dollars) compared to thousands," he said.

Counting the cost

The insect's damage extends beyond destruction of beautiful trees, experts said.

Bruce Kauffman, president of the Tennessee Entomological Society and senior technician with the University of Tennessee's soil, plant and pest lab, said the bug will spread over the Cumberland Plateau within this decade, carried by wind, deer, birds -- even people who brush against infected foliage.

"There's been a collection of seed so the species will not go extinct," he said. "But when we have hemlock deaths, we lose stream shade and raise water temperature in streams that support trout, other aquatic organisms and birds that build in (dense) cover. We don't have a replacement for that."

Dr. Jonathan Evans, director of the Landscape Analysis Lab at the University of the South, called the woolly adelgid a "daunting threat."

"From the standpoint of parks, visually it's a tragedy. And ecologically these hemlocks are critical," Dr. Evans said.

State and U.S. foresters also face the prospect of marred park lands and rising forest maintenance costs.

In Georgia, about $70,000 of the Chattahoochie National Forest's $3.3 million in stimulus money is going to fight the nearly invisible bug.

And in Tennessee, state parks officials have partnered with the Landscape Analysis Lab. Faculty and students will analyze GIS imagery of Fall Creek Falls State Park to help research and prioritize hemlock stands there.

Doing something

  • photo
    Staff Photo by Lesley Onstott
    John Thomason of ABC Tree Service looks for evidence of the hemlock woolly adelgid on a hemlock tree on the Signal Mountain property of Lee Davis. If left untreated, the bug eventually will kill the tree.

"It's important to do something," said Stuart Carroll, naturalist for the Fall Creek Falls State Park, adding that the lab's map analysis will help prioritize which hemlocks to try to save.

But he also said the data mapped by the lab will be important "even if we don't save one hemlock."

"Wouldn't it be interesting to see where the American chestnut was? But we'll never know that," he said. "But this study that will show there were 10,000 (or some number) trees in this one valley."

Researchers at the University of Tennessee at Knoxville and at four other schools in the Southeast have begun growing a predator beetle, now being released in the Great Smoky Mountains National Park and other areas. But the beetles can't be grown fast enough to keep up with the adelgid, officials said.

James Johnson with the Georgia Forestry Commission said the beetles may be the long-term answer, but the short-term response will have to be insecticides. And that will take more resources than state and federal forest officials can provide.

"It's spreading faster than we expected it would," Mr. Johnson said.

Homeowner help

Mr. Carroll and Mr. Johnson said homeowners can help by treating their hemlocks themselves or paying an arborist for the service.

"In Georgia, we have a program to help homeowners drench or inject the roots of their trees with insecticide," Mr. Johnson said. Homeowners can put a deposit on equipment, use and bring it back for a full refund. The insecticide itself is not very expensive, he said.

Gene Hyde, arborist for Chattanooga, said the only tree service he knows of locally offering hemlock service is ABC Tree Service in Harrison.

ABC's owner, Carl Absher, said he was galvanized to fight hemlock woolly adelgids when he visited his hometown in Virginia a few years ago and saw dying stands of hemlocks that he had stood among as a child.

"It's enough to make you cry back in those old-growth forests," he said.

The insecticide is taken up by the tree roots and transferred to the needles. When the bug bites, it dies.

  • photo
    Staff Photo by Lesley Onstott
    John Thomason of ABC Tree Service points out evidence of the presence of the hemlock woolly adelgid on a hemlock tree on Lee Davis' Signal Mountain property. If left untreated, the bug eventually will kill the tree.

The amount of insecticide needed depends on the size of the tree, he said. The adelgid takes seven to 10 years to kill a big hemlock. The treatments have to be repeated every three to five years.

On Signal Mountain in Walden, he estimates there are 500 or 600 infested trees, primarily in the brow and Summertown areas.

On Mr. Davis' Topside property, the graceful, giant hemlocks scattered in landscaped patterns over the lawn are more than just trees, Mr. Absher said.

"He has an historic property. Without those hemlocks, it would be an entirely different place," he said.

about Pam Sohn...

Pam Sohn has been reporting or editing Chattanooga news for 25 years. A Walden’s Ridge native, she began her journalism career with a 10-year stint at the Anniston (Ala.) Star. She came to the Chattanooga Times Free Press in 1999 after working at the Chattanooga Times for 14 years. She has been a city editor, Sunday editor, wire editor, projects team leader and assistant lifestyle editor. As a reporter, she also has covered the police, ...

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