photographed by Layne Strickler, National Park Service
This story was originally published in the July 2017 issue of Wonderful West Virginia. To subscribe, visit

Tiny bugs have put hemlocks—some of West Virginia’s oldest, biggest trees—in danger. But biologists are fighting back.

The meeting started on an ominous note. “The guy came to me and said, ‘Do you want the good news or the bad news?'” Dave Arnold recalls. His company, the Lansing-based whitewater outfitter Adventures on the Gorge, hired Colorado’s Bonsai Design in 2009 to develop its new Treetops Zip Line Canopy Tour. As part of the process, Bonsai had performed a survey of the property and was now ready to present Arnold with the findings.

The good news was, Adventures on the Gorge had the makings of an amazing zipline course. “The bad news was, there was some bug that was killing a lot of these trees.”

This photo taken at Blackwater Falls State Park
illustrates why dead and dying hemlocks are often called
“gray ghosts.”
photographed by Karen Felton

Bonsai called in a local arborist, who quickly identified the problem: hemlock woolly adelgid, a poppy seed-sized pest killing hemlock trees up and down the Appalachian range. Arnold had never paid any attention to them before. But once the arborist pointed them out, he began to notice the tiny white tufts attached to the undersides of the evergreens’ boughs. The bugs were everywhere.

Hemlock woolly adelgid, known to biologists as Adelges tsugae, are native to Asia and were first spotted in the eastern United States in 1951 near Richmond, Virginia. Researchers believe they probably hitched a ride on imported nursery stock. The adelgid spread from tree to tree on the wind, bird feathers, and animal fur and reached West Virginia’s Eastern Panhandle around 1992. The adelgid have now infested hemlocks across the state.

Infestations can be difficult to spot at first. The adelgid tend to start at the tops of trees and work their way down, which means it can be years before anyone realizes a tree is in danger. But as the bugs continue to feed on the trees’ sap—slowly draining the hemlocks of nutrients and making them more susceptible to environmental stressors like drought—there’s no mistaking the damage left behind.

Kristen Carrington, cooperative forest health
protection specialist with the West Virginia Department
of Agriculture, inspects an infested hemlock at Kanawha
State Forest.
photographed by Zack Harold

John Perez has gone to Pipestem Resort State Park each September for 15 years with his wife and kids. They ride the 3,600-foot aerial tramway down into the Bluestone Gorge, where they stay at the Mountain Creek Lodge and dine in its gourmet restaurant. Perez, a National Park Service biologist assigned to the New River Gorge, says the view heading into the gorge is always spectacular but, in recent years, he’s started to notice a change. “As you’re going down the tram, you notice the skeleton trees,” he says.

Perez says the adelgid have also devastated hemlocks near Seneca Rocks in Pocahontas County and White Sulphur Springs in Greenbrier County, as well as many hemlock stands in the Eastern Panhandle. Some areas are faring better than others. He hasn’t seen nearly the damage he expected in the New River Gorge, and believes that probably has to do with the climate there.

Hemlocks grow in the wettest areas of the gorge, so trees remain healthy enough to withstand infestation. The area also gets relatively cold winters, which helps knock back adelgid populations. Perez says biologists have seen as much as 95 percent mortality among woolly adelgid during winters where temperatures drop to single digits for several days in a row.

Unfortunately, the last two winters have been too warm to knock back the adelgid. Experts predict only about 10 percent adelgid mortality this year. If the trend persists, Perez says the woods around the New River Gorge might soon begin to look like forests elsewhere in the state—filled with grey ghosts where ancient green sentinels once stood.

“There’s No Question it Works”

Hemlocks make up a relatively small share of forests statewide, somewhere around five percent. But that percentage goes way up in the state’s most popular outdoor recreation areas. Along the Gauley River in the New River Gorge, Perez estimates 40 percent of trees are hemlocks. Humans seem to be attracted to the environments where hemlocks grow.

“The hemlocks create a mood,” Arnold says. “Any river guide who operates on the Gauley will tell you, there’s a different mood on the Gauley versus the New.” A friend of Arnold’s, one of Adventures on the Gorge’s original river guides, wrote a song about it. “The line is, ‘A river that seems to hide among the most rugged countryside,'” Arnold says.

Although hemlock woolly adelgid are actually small and black, like poppy seeds, the bugs secrete a waxy white covering to protect them from the elements.
photographed by Zack Harold

But it’s more than just a mood. The trees are crucial to their ecosystems. Their deep, dark shade keeps mountain streams cool enough for brook trout and Cheat Mountain salamanders to flourish. Critters like the hermit thrush, black-throated green warbler, and northern flying squirrel depend on the trees for shelter.

A West Virginia forest without its hemlocks would be a much different—and much diminished—place from the woods we know today. That’s why biologists are using every weapon in their arsenals to defeat the hemlock woolly adelgid.

When Perez first encountered the adelgid, working for the National Park Service in Virginia, he went out with crews in pickup trucks, driving narrow access roads spraying insecticidal soap and horticultural oil up into the hemlocks. It was labor intensive and not very effective—the chemicals had to make contact with the adelgid before they would work.

Eventually a new type of insecticide came into use, which exploits the tree’s natural circulation system to carry the poison directly to the pest. Now, workers can bury a tablet in the soil near the tree’s root system or, if it’s a large tree or located by a stream, inject the insecticide directly into the trunk.

Workers perform a stem injection on a stand of hemlocks in the Monongahela National Forest. Old trees and those located near rivers and streams receive stem injections. In
other cases, workers bury insecticide tablets in the soil near the trees‘ root systems.
photographed by Amy Hill, U.S. Forest Service

Adventures on the Gorge launched a large-scale treatment program for its hemlocks after Bonsai Design discovered adelgid on the property. The company now treats around 10,000 trees with either root treatments or core injections. So far, Arnold says they haven’t lost a single hemlock to the adelgid. “There’s no question it works. The problem is, it’s perpetual and it costs a lot of money,” he says. Adventures on the Gorge spends thousands of dollars each year on the chemicals alone. Labor costs even more.

Those limiting factors—time and money—also come into play in the state’s efforts to control the adelgid infestation. Bayer, which manufactures the root treatment tablet Coretect, donates 54 cases of the product each year to Cathedral State Park in Preston County, a park known for its stands of virgin hemlocks. Other parts of the state aren’t so lucky. Agencies like West Virginia State Parks and the Department of Agriculture treat as many hemlocks as they can but, with budgets growing tighter all the time, there isn’t enough insecticide or manpower to go around.

But money and labor aren’t the only downsides to using insecticides. The chemicals don’t work well in older trees, which have circulation systems that don’t run as smoothly as in younger plants. There’s also some worry about the effects those insecticides are having on the environment.

The National Park Service, in partnership with West Virginia University, recently received research grants to study the effects of insecticide use in hemlocks. Perez says it’s important work because, nationwide, biologists are treating tens of thousands of trees each year against the adelgid. He worries the chemicals might be bioaccumulating in the environment, climbing up through the food chain. “We have to have some way that doesn’t involve chemical treatments,” he says. “We may be killing the forests to save the trees.”

Meet the Beetles

Perez says the best hope—for both hemlocks and the environment at large—is to find a biological control to balance the scales against the adelgid. Right now, the best candidate seems to be a tiny beetle named Laricobius nigrinus. There’s no common name for the bug, so Perez and company have taken to calling them “Lari” for short. One biologist at the NPS even put a bumper sticker on her boyfriend’s car that says “I ❤ LARI.”

The beetle is native to the Pacific Northwest and has generally the same life cycle as the adelgid, with separate generations in the spring and winter, which means it feeds on the pests when they are most active. “That’s why the western hemlocks don’t have a problem. Beetles eat the adelgid and they never become a problem,” says Kristen Carrington, a cooperative forest health protection specialist with the West Virginia Department of Agriculture.

Newly released Laricobius nigrinus beetles crawl onto a hemlock branch.
The beetles, native to the Pacific Northwest, have the same life cycle as the
hemlock woolly adelgid and feed on the pests.
photographed by Layne Strickler, National Park Service

Both lab and field tests have shown the beetles are effective at fighting woolly adelgid populations. But there’s a problem. There aren’t enough beetles to go around. West Virginia mostly gets its Lari from a rearing
facility at Virginia Tech, but there’s such a high demand, the whole state might receive only 3,000 or 4,000 beetles per year. “You really need to just drop boatloads of beetles into an area, hoping you’ll start seeing some effects,” says Amy Hill, a Morgantown-based entomologist with the U.S. Forest Service. Due to the limited supply, state and federal agencies have agreed to release beetles only in the New River Gorge and Blackwater Falls State Park.

It’s also unclear how well the beetles are doing in the wild. Biologists try to find them after they’ve been released, in hopes they have established self-sustaining colonies. Perez is usually able to find some in the New River Gorge, although Carrington hasn’t had much luck when she goes out into the field. After the polar vortex of 2014, beetles were nowhere to be found. “We’re hoping there are more up there than we know about,” Hill says. “You don’t know what’s going on at the tops of the trees.”

Data is still limited at this point, but there are positive signs. In the 10 years since biologists began releasing the beetles in the New River Gorge, “we cannot detect a significant change in the health of those hemlocks. Which is good,” Perez says. “It’s fair to assume the biological controls, the beetles, are having a positive effect at controlling the hemlock woolly adelgid.”

Other projects are looking for natural approaches, too. There’s a stand of trees in New Jersey that appear to be impervious to attacks by the woolly adelgid. Researchers aren’t sure if that’s because the trees themselves have a natural resistance to the bugs or if there are other environmental factors at play. To find out, several states are now growing seedlings from those “bulletproof” hemlocks.

West Virginia got 10 seedlings in October 2015, which are now growing in Kanawha State Forest. Carrington introduced adelgids into the trees in April of this year and will go back a few times every year to monitor their progress. If the trees prove to be resistant to adelgid, Carrington imagines a day when the seed cones might be distributed up and down the East Coast, helping states replace trees that have succumbed to infestation.

Preserving Hope

We have been through this before, of course. The forests of today are very different from the woods your great-great-grandfather knew. And it’s all because of an invasive species.

It is estimated that, prior to 20th century, a quarter of the trees in the Appalachian Mountains were American chestnuts. The trees stood up to 100 feet tall and provided a valuable food source for their ecosystems. But then a fungus arrived from Asia on nursery stock. It spread tree-to-tree on the wind, rain, and animals until almost all of North America’s 4 billion chestnut trees were dead.

Perez remembers going into the woods as a forestry student at WVU to study the stumps of chestnut trees killed off during the blight of the early 1900s. “We have no idea what that forest was like,” he says. “We have little data on what the conditions were in a chestnut forest before they died. I didn’t want that to happen to the hemlocks.”

In 2015, West Virginia received 10 hemlock seedlings that might be
resistant to hemlock woolly adelgid. They have been inoculated with
adelgid and will be monitored in years to come.
photographed by Zack Harold

When Perez transferred to the New River Gorge in 1997, he knew adelgid were on their way, so he secured money to establish a long-term monitoring project. The National Park Service was able to collect seven years of such
data before the pests invaded their monitoring plots. “We know everything about these plots,” Perez says—what plant and bird species were present, the density of the vegetation, the moisture levels and chemical makeup of the soil, the composition of the lower, middle, and top levels of the canopy, even how many pounds of dead leaves were on the ground.

Biologists are hopeful that, eventually, something will stop the adelgid. It might be Lari beetles or pest-resistant hemlock trees or some other biological control. When that day comes, Perez’s data will allow future conservationists to begin repairing the damage the tiny black bugs have caused.

Things might not ever be exactly as they were before the woolly adelgid arrived. But at least future generations will not have to walk out in the woods, stare at a stump, and wonder what it must have been like to stand in the deep, dark shade of a hemlock tree.

written by Zack Harold