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Healthy Branch
Healthy branch. The hemlock grows well along streambeds, providing shade for fish.
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Evidence
Evidence of presence. The adelgid leaves puffy white egg masses.
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Ashley Lamb
Ashley Lamb. She’s at work on a study of a new beetle to combat the woolly adelgid.
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Hemlock Woolly Adelgid
The hemlock woolly adelgid. It is relentlessly eliminating a species.
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The Tech Team
The Tech team. From left: Dr. Scott Salom, Dr. Theresa “Tree” Dellinger, Ashley Lamb, Brian Eisenback and David Mausel; they’re raising beetles that may control the HWA.
Scott Salom is a tall, good-looking, sandy-haired, Long Island native who recruits the members of his team as assiduously as any gridiron coach. An associate professor of Forest Entomology at Virginia Tech, Salom knows the kind of player he’s looking for: one who is, “passionate, dedicated and who won’t give up until he has accomplished what he set out to do – the student who knows how to fight,” he says. “Research projects are never easy. You have to have a lot of fire and something to prove. You’ve got to get interested in the story.”
The coach is interested in the story. Has been since 1994, when, as a relatively new recruit himself – he came to Tech in 1990 – he attended a meeting in Shenandoah National Park just as the U.S. Forest Service was about to begin pouring money into a now-massive effort to control the hemlock woolly adelgid (HWA). HWA is a formidable opponent, a nearly invisible aphid-like insect who is nonetheless capable, in league with a few hundred million of her cohorts (all HWA are female), of sucking the life out of a hemlock tree in the space of four years. Big, 500-year-old old-growth giants, or understory saplings awaiting a place in the sun, it doesn’t matter how big or how small. Assaulted by legions of HWA, eastern and Carolina hemlocks are toast. HWA doesn’t belong here, but she has made herself abundantly at home.
To take on the HWA challenge, the US Forest Service is tapping the best researchers it can find, and it’s found a lot of them at Virginia Tech. The stakes in the game couldn’t be higher. Hemlocks grow from the Canadian Maritimes west to Minnesota and south to northern Georgia. In the 55 years since HWA was first noted in the East in a park in Richmond, it has invaded about half that territory, most of it in the last 20 years. Already it has killed all the hemlock stands in Shenandoah National Park and has begun turning hemlocks in the Smokies, where it was first detected in 2002, into gray ghosts. Without an all-star team working on the problem, Carolina hemlocks may be wiped out altogether. Ditto eastern hemlocks south of the Mason-Dixon line, and in a lot of places north of it too.
Salom wangled an invitation to the Shenandoah meeting.
“I got in touch with [U.S. Forest Service research scientist] Mike Montgomery, who I knew, and made a plug,” he says. “I said I would like to get involved. The number of collaborators they had then was still small. I went to the meeting, and got to know everybody involved with HWA.”
Mark McClure, the Connecticut scientist who raised the alarm about HWA in 1986, had studied HWA’s life cycle up north.
“We volunteered to look at it here in Virginia,” Salom says. “We started with that.”
By “we,” Salom means the team of graduate and postgraduate researchers that he and assistant coach Loke T. Kok, head of VT’s entomology department and a biological control expert, have assembled to explore key aspects of the HWA problem.
Correctly ascertaining that the forest service would funnel most of its initial money into biocontrol, Salom and Kok submitted a proposal to look at Laricobius nigrinus, a predatory beetle native to the Pacific Northwest. It didn’t hurt that Salom had earned his Ph.D. at the University of British Columbia and knew Lee Humble, the Canadian Forest Service research scientist who first noticed L. nigrinus munching on HWA on hemlocks in a seed orchard on Vancouver Island.
In 1997, Salom paid Humble a visit. He returned with the beetle and the team’s first key player, Gabriella Zihali-Balogh, who would work on the beetle – and her Ph.D. – at Tech.
Though Zihali-Balogh, “was not really a forest entomologist, she was passionate about her work and absolutely relentless when it came to getting the job done,” Salom says.
The job was to determine whether L. nigrinus was a good candidate to control the adelgid in the east. The work involved testing the beetle to see whether it preferred a diet of HWA to other adelgids, aphids and mealybugs – which it did – and studying its life history. Zihali-Balogh got her Ph.D.– she’s since left VT – and L. nigrinus got approved for release.
The next problem Salom’s team had to tackle was figuring out how to mass-rear L. nigrinus. Lab-rearing beetles is not easy, especially one like L. nigrinus whose life cycle includes a months-long summertime nap underground. Problems with mold, desiccation and even starvation if the beetles emerge too soon, can ensue.
Working out the rearing protocols fell to Ashley Lamb, another Humble protégé, who came to Tech to work on her master’s and stayed to complete a doctorate. She’s now engaged in a two-year postdoctoral study of a new beetle, an as-yet-unnamed Japanese Laricobius she calls “Samurai Lari.”
Lamb collected 309 of the new beetles on a trip to Japan last spring. Upon her return, she left them in the keeping of lab specialist Tom McAvoy, and within days was off on a second collecting trip to China. The Chinese trip ended in disaster for the beetles she tried to bring home. Detained overlong in customs, none were alive by the time they reached the quarantine lab in which she works, on the outskirts of the Tech campus.
The third of Tech’s star players is David Mausel, whose three-year Ph.D. project has been to track L. nigrinus’ success in establishing and reproducing in the wild. Thanks to the beetle’s success in reproducing at release sites from Massachusetts to Georgia, Mausel’s name is well known on the HWA battlefield.
Still other members of the VT team have taken on important aspects of the problem of halting HWA’s forward drive.
Corey Broeckling, now a Ph.D. student at Colorado State, studied L. nigrinus’ response to olfactory cues to discover how the beetle finds its prey.
Brian Eisenback examined the effects that the insecticide Imidacloprid – the most effective chemical control for HWA – has on predators that feed on adelgid on treated trees. Eisenback took on that project despite the fact that, “he didn’t feel as though he had a strong chemistry background,” Salom says.
Eisenback performed well enough to attract the attention of the American Chemical Society, which invited him to make a presentation at its meeting this March.
Robbie Flowers, now a state entomologist in Oregon, tackled the potential competitive interactions between L. nigrinus and two ladybird beetles that also eat the adelgid.
Then there are the team members at VT’s mass-rearing facility: Theresa (“Tree”) Dellinger, Carrie Jubb and their assistants.
Dellinger, who earned her Ph.D. at VT in 2003, was in charge of mass rearing until recently, when she handed the responsibility off to Jubb. Now she’s working on another project – with Bayer, the pharmaceutical giant that developed Imidacloprid – searching for safer ways to apply the chemical to adelgid-infested trees. Each of the current methods has drawbacks. Injecting Imidacloprid into hemlocks wounds already stressed trees, and soil applications risk chemicals migrating into a body of water where they are toxic to aquatic organisms.
VT’s team wins consistent high praise from forest service officials. The two Laricobius beetles represent a “light at the end of the tunnel,” says Brad Onken, who heads the HWA control effort.
At some of the L. nigrinus release sites, the trees look a little better than they did.
As for Samurai Lari, Lamb says it’s “full of surprises” and is more voracious, faster-developing and more cold-tolerant than its American cousin. Onken is chomping at the bit to get it out the door.
“I’m always afraid to get too excited about one predator,” he says, “but this one will definitely be a player once it’s okayed for release.”
After that happens, someone will need to follow up on Samurai Lari in the field the way Mausel has with L. nigrinus. That means more recruiting for the coaches, but Salom loves it. He’s always on the lookout for future players with that passion, that spark. Once they’ve signed on, he suggests a kind of basic training – a stint as a technician in the insectary, doing the tedious housekeeping chores essential to keeping thousands of developing beetles alive and fed. Such work separates the players from the washouts, and by the time the survivors begin their graduate work, “they know the system,” Salom says. “After six months in the insectary, they’re dying to get outside and begin their own projects.”
WANT TO HELP?
The Friends of the Blue Ridge Parkway established a “Preserve the Hemlocks” effort several years ago, and has agreed to continue to support the Virginia Tech HWA research program’s goal of finding and preserving the Southeast’s tallest and largest hemlocks if Roanoker readers like you will help.
There are two ways to do it. Mail donations to: Friends of the Blue Ridge Parkway, P.O. Box 20986, Roanoke, VA. 24018, or call 1-800-228-7275. Please specify that the gift is to go to “Save Our Hemlocks.” You can also donate online at blueridgefriends.org.