If you've walked in a hemlock forest recently, along a babbling stream where native trout hide, you'll notice something extremely sad-the hemlocks are dying. They appear a sickly gray-green instead of shiny and dark green. Branches have died back, needles are sparse and scant, and in many places, tree ghosts are all that remain. Sunlight has penetrated the forest making it disturbingly hot in the summer. The largest of the majestic trees have fallen and are in their graves.
The hemlock woolly adelgid, a tiny insect that sucks out the life fluid from the base of the hemlock needles, is responsible.
The insect, a native of Japan, was discovered in the United State's Pacific Northwest in 1924 and in the Northeast in the 1950s. Its population now covers 40 percent of the native range of the eastern hemlock, including all of the mid-Atlantic states where hemlocks grow.
"The hemlock woolly adelgid is present in every county in Virginia," said Chris Asaro, forest health specialist for the Virginia Department of Forestry. "All the hemlocks are dead in the George Washington and Jefferson National Forests and the Shenandoah National Park has lost 90 percent of its hemlocks."
Foresters warn of a disaster similar to the blight that eliminated chestnut trees from the Appalachians. There were once more than 3 billion chestnuts in the eastern United States at the beginning of the 20th century. They accounted for a quarter of the trees in the Appalachian Mountains. They were the most important nut-producing tree in the forest-and the most economically valuable. Now they are gone.
The eastern hemlock is Pennsylvania's state tree. There are more than a dozen prime old growth hemlock stands in the state, some trees several hundred years old. They cool the streams and provide crucial habitat for native trout. In fact, brook trout are twice as abundant in streams lined by hemlocks as those lined by hardwoods, according to the United States Geologic Survey.
"You lose the hemlocks; you say good-bye to the trout. It is a very important ecological mix," said Dr. Donald Eggen, a forest health manager with the Pennsylvania Bureau of Forestry.
Foresters across the region are on the problem. "We've been treating high-profile stands in parks and picnic areas using injection needles with much success," says Joseph Fiedor, assistant state forester of Pennsylvania Field Operations (Injection needles pump a chemical into the ground; the chemical is absorbed by the hemlock and helps it repel adelgids). "But it is a big forest out there and this is like a drop in a bucket."
Beetles that love to eat adelgids offer one hopeful solution. The Pennsylvania forestry bureau and New Jersey Department of Agriculture cooperate to raise beetles that thrive on adelgids. Pennsylvania foresters collect "Grade A" infested hemlock boughs, covered with insects, and ship them to New Jersey where the hungry beetles devour them, grow up strong and proliferate, then get mailed back to be released in Pennsylvania forests.
Scientists at Virginia Tech, meanwhile, are testing a Pacific Northwest beetle and a beetle from Japan that feed on all stages of the hemlock woolly adelgid.
A fungus strain that kills hemlock woolly adelgids has also been discovered. If the foresters can figure how to put it into a spray and disperse it with helicopters, the hemlocks might stand a chance.
Homeowners and landowners can help control the pest. If your hemlocks become infected, contact your local extension office to report the infestation and get information about treatments. Horticulture oil sprays and soaps have shown some success, as have pesticides. To prevent infestations, locate bird feeders away from hemlocks in your yard.
There's some good news that comes with the cold of winter-the hemlock woolly adelgid's spread is related to elevation and winter conditions. Colder weather slows them down and they have not moved into areas where winters are severe.
Although many state funds have been cut, the federally funded Hemlock Woolly Adelgid Initiative continues to support research and development. This program is largely responsible for the work being done in New Jersey, Pennsylvania and at Virginia Tech.
"We have some pretty passionate folks working on this," said Scott Salon, professor of entomology at Virginia Tech. "They really want to save these trees."
The chestnut blight that ravaged the eastern forests taught us how devastating an invasive like the woolly adelgid can be. Less than a century ago, chestnuts ruled our forests. Now scientists struggle to find the few that might have survived with the hope that the species can be re-introduced in the future.
Today, foresters are collecting and saving the seeds from resistant hemlocks that have fought the fight with the hemlock woolly adelgid and pulled through. If all we can do is replant the forest, the seeds will make it possible.
In the meantime, get the children out for a walk in cool, dark eastern hemlock forests, for they are disappearing rapidly.