A healthy hemlock retains green needles, right, unlike one under attack, left. Photos © Chris Evans, River to River CWMA; and Sven-Erik Spichiger, Pennsylvania Department of Conservation and Natural Resources.
The Joyce Kilmer Memorial Forest, a rare tract of virgin forest east of the Mississippi, is intact today primarily because it is located in one of the most remote corners of the North Carolina mountains. But escaping the saw, as unlikely as it was in a time of relentless clear-cutting, proved to be only a temporary victory for the massive eastern hemlocks that give the 3,800-acre preserve much of its unique character.
While steep ravines carved out by rolling creeks winding around moss-covered boulders deterred loggers in the early twentieth century, they are doing nothing to stop the relentless and stunningly destructive hemlock woolly adelgid. The tiny insect invader from Japan, barely visible to the naked eye, reached Joyce Kilmer’s 130-foot-tall trees in 2001, and massive efforts by the U.S. Forest Service to combat it seem to have had little effect.
“The prognosis is very poor,” says Forest Service technician Virginia Gibbs, who works out of the Cheoah Ranger Station in the Nantahala National Forest “Everybody got caught off-guard. We knew it was coming, but the intensity…nobody was prepared for it. Nobody.”
In 2004, scientists released thousands of beetles, Pseudoscymnus tsugae, also from Japan, that are natural predators of the tiny insect. They followed that release with chemical soil injections, hoping that the double treatment would save the sick hemlocks. But underneath Joyce Kilmer’s massive canopy, it’s clear that the trees—many of which are nearly 400 years old and more than four feet in diameter—are well on their way to succumbing. The deep green of the forest has been replaced by sickly gray as millions of woolly adelgids suck the life out of every needle, essentially starving the hemlocks to death.
Gibbs, an eighteen-year Forest Service veteran, says she’s never seen such a relentless and deadly scourge as the 100 percent mortality rate observed in infested eastern hemlocks. “The adelgid is not like the Southern pine beetle. It has the capability of wiping out an entire species. It goes after trees of all sizes, [even] seedlings. That’s what makes it different. No other pest we’ve had has ever done that, other than the chestnut blight. That’s the only thing I can compare it to.”
Will Blozan, a professional arborist, was on the front line when the Forest Service released the adelgid-devouring beetles in May of 2004, climbing into the hemlock canopies to place about 2,000 of the predators in each tree. Today, there’s little sign that his work has had positive results. “I’ve been to a dozen or so beetle release sites, and worked on two of them, and all of them have miserably failed as far as I can see,” he says. “The trees in Kilmer are dead unless they’ve been treated chemically. That species of beetle isn’t working at all. It’s such an undignified death for such an amazing tree.”
The problem may lie in the fact that the thousands of beetles released were no match for woolly adelgid populations that had exploded into the tens of millions, feeding on defenseless trees already stressed by years of ozone pollution, deepening drought and unusually hot summers. “A tree can take light infestation of adelgids, but they can’t survive a bombardment. We’ve released 43,000 beetles. A more effective number would have been 43 million,” Gibbs says. “[The beetles] are still out there, which makes me very happy. But really the only way that we can tell that anything is working is if the trees stay alive.”
Research conducted four to seven years after the beetle releases has shown that hemlocks can recover, as long as the trees were still fairly healthy at the time of treatment and environmental conditions remained favorable—specifically, cool weather and plenty of rain. None of those conditions have existed in Joyce Kilmer, where drought and heat have persisted in the summers. Cold winters also seem to slow the hemlock woolly adelgid, but winters in western North Carolina, not nearly as cool as in the Northeast to begin with, have been abnormally warm.
Gibbs thinks it may be time to concede that the largest trees cannot be saved and to concentrate on smaller ones. She is optimistic the war to preserve the species can be won in the long run, as long as the Forest Service fights the right battles.
“You’d have to have many years to establish a true beetle population,” she said. “There are hundreds of thousands of young hemlocks coming up, and in my mind if we can treat small areas—scattered, dotted, all over the Southeast and up north—we can save a remnant of the species. To me, that’s critical. As far as hope for preservation of the species, there’s huge amounts of hope. But if we continue to concentrate only on the big trees, we’re wasting time.”