The invaders will come from the east, but it's unlikely anyone will see them cross the state line.
If fact, they may already be here, silently sucking the life from their victims in some of Kentucky's wildest and most beautiful places.
The invaders are tiny insects called hemlock woolly adelgids (a-DEL-gids). They attack only hemlock trees, the tall, stately evergreens often found along creeks in the eastern half of the state.
The adelgid is the latest in a series of insects and diseases attacking our forests. American elms and chestnut trees were wiped out in the last century. Pines were killed across thousands of acres a few years ago. Oaks and ashes also are in danger. Even the dogwood, with its delicate spring blooms, is disappearing from the mountains.
Hemlocks are not especially valued for their wood. But biologists and forestry experts say they occupy a vital niche in the region's ecosystem. Their evergreen needles shade headwater streams, keeping them cooler in the summer and warmer in the winter.
They are important to tourism because they attract people to places such as the Red River Gorge and Blanton Forest State Nature Preserve in Harlan County, where some of the old-growth hemlocks are four feet in diameter and well over 100 feet tall.
To get ready to combat the adelgid, the state is asking for help finding stands of hemlock. Officials also are asking people to be on the lookout for the white woolly tufts on trees that would signal that the insect has arrived.
But no one is optimistic that the adelgid can be stopped.
If most of the state's hemlocks die, experts say, it will be like losing a part of the puzzle that is the region's ecosystem.
Hemlocks are important to aquatic life, and several species of songbirds seek shelter in their branches.
But no one will know the full effect of losing hemlocks until after it happens.
"It's like if you took the back of your computer off and started snipping wires -- you can't expect it to function normally if you start removing pieces and parts," said Steve Bonney, a biologist for the Kentucky Department for Fish and Wildlife Resources.
Asian hemlocks not affected
Adelgids are oval, reddish-purple insects. Adults are only one-thirty-second of an inch long.
They are natives of Japan and China, but do little damage to hemlocks there.
Females do all the damage here. They feed by piercing the base of hemlock needles and drawing out sap.
They lay eggs twice a year. In October, preparing for winter, they cover themselves and their eggs in a waxy material that looks like wool.
An infected tree usually dies in 5 to 10 years.
Adelgids were first noticed in this country near Richmond, Va., in the 1950s.
They attack two species, eastern hemlock and Carolina hemlock. Kentucky has only eastern hemlocks. Adelgids have spread to 16 states, including portions of Virginia, West Virginia and Tennessee that are very near Kentucky.
In some places, notably along the Delaware Water Gap, more than 80 percent of the hemlocks have been killed.
The best hope for hemlocks is saving those that have been planted in yards. They can be sprayed with insecticidal soap. Or a chemical can be injected into the ground around the trees, or into the trunk.
But the chemicals can't be used in the many places where they could get into creeks. And spraying or injecting entire hemlock stands would be expensive and, in remote locations, impractical.
"I would like to be optimistic, but ... it's just going to be impossible to get to many of these trees," said Tim McClure, a forest health specialist with the state Division of Forestry.
Fighting bugs with beetles
Scientists are looking for a natural predator that can eat the adelgids, and have come up with several possibilities.
At the University of Tennessee, for example, researchers are raising a black lady beetle that eats only hemlock woolly adelgids.
Its scientific name is Sasajiscymnus tsugae. It doesn't have a common name.
"We call it S.t.," said Carl Jones, the head of UT's department of entomology and plant pathology.
S.t. is very, very small, which makes working with it difficult. Jones said it is the size of the period at the end of this sentence.
Despite its size, S.t. can eat thousands of adelgids in a year.
UT released 25,000 beetles in the 2003-2004 season, and more than 100,000 last year. An equal amount are being released this year.
The research and release is being paid for by the Great Smoky Mountains National Park, the Forest Service, Tennessee state funds and private grants.
Are the beetles doing the job?
No one knows yet, Jones said. The program was so urgent that the beetles were raised and released before money was allocated to assess their effectiveness.
There is evidence that adelgids are declining or no longer increasing in areas where S.t. has been released. Jones said it would be a year before a recently funded study can quantify those observations.
But S.t. or other predators can't be released into Kentucky forests before the adelgid arrives. They would starve.
Prevention in progress
Many foresters and others think predator beetles will never wipe out adelgids.
Rex Mann, an emergency response expert with the Forest Service's office in Washington, D.C., says the solution is breeding insect-resistant hemlocks.
Mann was a longtime official with the Daniel Boone National Forest and still is based in Kentucky. He also is involved with efforts to bring back American chestnuts, which were virtually wiped out by a blight in the early decades of the 20th century.
The few surviving American chestnuts are being cross-bred with blight-resistant Chinese chestnuts, a process Mann calls "speeding up evolution by thousands and thousands of years."
The same thing can be done for hemlocks, he said.
Although eastern and Carolina hemlocks are being attacked by the adelgid, western hemlocks don't seem to be bothered.
That might be because their needles are too thick for the insect to pierce, Mann said.
Kentucky officials are formulating plans on what to do when the insect arrives here. McClure, the Division of Forestry specialist, said the state may come up with a plan similar to one being developed in Tennessee.
That plan calls for setting priorities on treating some trees because of their ecological and tourism value, and letting others face the adelgid by themselves.
McClure is traveling around Eastern Kentucky looking for and checking hemlocks.
Songlin Fei, a University of Kentucky forestry professor, is planning an in-depth survey of where the hemlocks are by using satellite photography.
But, even as the state asks people to be on the lookout for adelgids, no one is quite sure what will happen when they show up.
"That's what we're looking into right now," McClure said.Kentucky Herald-Leader
