by Jedd Ferris

The sign says: “The forest is changing. Watch for Falling Trees.”

Falling trees aren’t exactly what you want to be worried about on your next outing. But that’s what a signs says along the Appalachian Trail a short ways into the southern end of Shenandoah National Park. Unfortunately “changing” actually means “dying.” Over 85 percent of the Shenandoah’s hemlock trees have literally had the life sucked out of them by the hemlock woolly adelgid, an invasive insect introduced from Asia that is chewing up Appalachia’s most beloved evergreen.

The alien adelgid is attacking forests from Maine to Georgia-causing an ecological disaster similar to the American Chestnut Blight of the early twentieth century. Hemlocks have been wiped out in Virginia, and the adelgid is spreading southward into North Carolina and Georgia at an alarming speed.

“The adelgid populations are exploding, and they’re advancing rapidly southward,” says Linda Randolph, a silviculturist with Pisgah National Forest in North Carolina. “We don’t know yet if we can stop the adelgid or not, but the hemlocks are certainly worth fighting for.”

One of the most celebrated and aesthetically pleasing old growth trees in the Appalachians, the hemlock plays a critical role in protecting mountain streams and wildlife. It comprises about 10 percent of the Southern Appalachian forest and is the most shade tolerant evergreen in the East. As a result, it protects native trout and other aquatic life by controlling water temperature and filtering excess nutrients. In the winter, several species of warblers and other wildlife congregate in hemlock groves, which provide protection from snow cover.

“Without the hemlock, entire ecosystems will disappear,” says Ryan Franks, president of Appalachian Tree Care, a Boone, N.C.,-based company that specializes in treating hemlocks. “It’s going to make our woods that much less diverse.”

The adelgid arrived in the U.S. fifty years ago, but warmer winter temperatures, air pollution, and increased development and logging near national forests have accelerated the adelgid’s advancement. Typically transported by birds (the adelgid itself cannot fly), the parasite sinks its mouth into the base of the hemlock needle and sucks out the sap that would normally be used to photosynthesize, robbing the tree of nutrients. Trees turn rust-colored and die within three to six years of infestation. Compounding the problem is that adelgids are parsinogenic, meaning they reproduce on their own. Each of the white cotton sacks that form on the needles-the most tell-tale sign of an infested hemlock- hold 200-300 offspring. By the third or fourth generation the tree is doomed.

But there is hope. Beetles that feed exclusively on the hemlock woolly adelgid have been introduced at selected sites in the Appalachians. In some studies, the beetles have gobbled up 40-70 percent of the adelgids, but it’s still unclear whether enough beetles can be reared in time, especially with only two major beetle-raising laboratories operating in the Southeast.

“If a tree is infested, beetles are probably not going to save it,” says Randolph. “The beetle populations need to build at the same time as the adelgid. It’s just basic insect dynamics. If you have 1,000 predator beetles going after four billion adelgids, they just can’t eat that much.”

Forest managers have resorted to treating heavily-infested hemlocks with soil injections of the insecticide Imidocloprid. Though it is cost-prohibitive to treat thousands of acres of hemlocks with the insecticide, biologists from Shenandoah to the Smokies hope to save a few clusters of hemlocks as genetic reserves for future reintroduction.

For outdoor enthusiasts, favorite trails could be blocked or cluttered with downed hemlocks in the coming years, especially trails near streams. Falling trees could force closures where public safety is a risk in national forests, parks, and designated camping areas.

“A lot of our trails and recreation sites are in hemlock areas, so public health and safety is something we have to be concerned with,” says Rusty Rhea, an entomologist with Forest Health Protection that assists state and federal agencies combating the adelgid. “If we don’t intervene soon, we’re going to lose stands across the board.”

Adopt a Hemlock

Blue Ridge Outdoors needs your help in saving the hemlock-Southern Appalachia's signature evergreen. Readers can adopt an old-growth hemlock tree in a nearby national forest through our Save-a-Hemlock campaign. For $25 to $50, you can rescue an ancient hemlock. Adopted trees are treated with an organic injection that’s safe for the tree and the surrounding forest and watershed. The injection protects the tree from the hemlock wooly adelgid and kills any adelgids currently infesting the tree.

You'll also receive a photograph of your adopted tree, a quarterly newsletter, and a map showing you where to visit your hemlock in Southern Appalachia's national forests.

Your donation is tax-deductible, and 100% of it goes to protecting the last remaining old-growth hemlocks. You'll be helping to provide a genetic repository of hemlocks for future regeneration. Best of all, you'll be saving the Southeast's most beloved and biologically significant evergreen-a tree that also shades Southern Appalachia's most popular hiking, biking, and running trails.

Join Blue Ridge Outdoors and readers across the region in rescuing our old-growth hemlock forests, one tree at a time. To adopt your hemlock, visit www.blueridgeoutdoors.com and click on Save-a-Hemlock. You can also email will@blueridgeoutdoors.com or call 828-225-0868 for additional information.