Hope for NC forest hemlocks comes in shape of tiny predator

Laricobius nigrinus, dubbed the Lari beetle, feeds on hemlock woolly adelgid egg sacs (white blotches) on a stem at Grandfather Golf & Country Club.
Laricobius nigrinus, dubbed the Lari beetle, feeds on hemlock woolly adelgid egg sacs (white blotches) on a stem at Grandfather Golf & Country Club. jsimmons@charlotteobserver.com

The granddaddy trees of North Carolina’s mountains are skeletons on many slopes.

Hemlocks that might have lived for 800 years can die in as few as five, victims of tiny, sap-sucking bugs.

Gray hemlock stands pock the Great Smoky Mountains, the most-visited national park, where 80 percent of the oldest trees are dead. More than half of North Carolina’s forest hemlocks have died in the past 15 years.

But there’s hope amid the devastation.

The beetle Laricobius nigrinus, a native of the Pacific Northwest known as Lari, feasts on the aphid-like insects called hemlock woolly adelgids. Lari’s proving ground is Grandfather Golf & Country Club in Linville.

The 14,000 beetles released there since 2008 have replaced the chemicals once used to control the adelgid. Eighty-five percent to 90 percent of the club’s hemlocks have survived, and many have put on growth spurts.

“We’re back to the point where we were before the adelgid hit,” said golf course superintendent Pete Gerdon. “We bring people in now, who know about this problem, who are stunned” by the rebound.

The beetle has scored similar, if less dramatic, success across Western North Carolina. Adelgid experts are more optimistic about the trees’ survival than they were just a few years ago, when infestations peaked.

Lari’s arrival in the North Carolina high country was the work of Gerdon’s friend Richard McDonald, a Watauga County entomologist who set out to save the hemlocks.

Researchers discovered in 2006, several years into the infestation, that the adelgids previously traced to Japan are also natives of the Northwest. Because hemlocks there still thrive, McDonald knew, they must have native predators.

McDonald’s business, Symbiont Biological Pest Management, uses predator insects and other ecological controls on insect pests. The strategy works for broccoli fields and golf courses.

It would also work, he reasoned, for hemlocks.

McDonald convinced Grandfather’s directors to send him to Seattle for two weeks in 2008 to collect Lari beetles.

Government agencies had studied Lari for six years, making sure it wouldn’t cause problems in its new territory, before approving releases in 2002.

Fifty-nine trips later, McDonald has released Lari in dozens of places in the Grandfather region and as far west as Cashiers.

“I thought we were doomed,” he said of the hemlocks. “The data kept telling us we were doomed until about 2009, when the trees stopped dying.”

McDonald says the nearly 150,000 beetles he’s collected in the Northwest, and from the growing North Carolina population, have multiplied into the millions. “I started finding beetles everywhere I looked.”

‘Seeing is believing’

Jesse Webster, a forester at the Great Smoky Mountains park, says beetles are now the best long-term hope for the surviving hemlocks. He calls McDonald their Johnny Appleseed.

“I have seen what he’s talking about,” Webster said, “and seeing is believing.”

Lari beetles have established a foothold in the park, Webster said, and seem to be maintaining a predator-prey balance with the adelgid.

Hemlocks in the park’s half-million acres can now go longer without being treated with chemicals, and smaller amounts are needed when they are treated. Recent frigid winters, which control the pest in the Northeast, have helped by killing many adelgids.

The Smokies’ hemlocks are still producing seeds for a new generation. Research is underway to help restore the species. And the search for more adelgid-munching beetle species such as Lari continues.

“We see a lot of hope for the future,” Webster said. “We’ve seen that tsunami wave, and now we’re collecting the pieces and establishing the forests of the future.”

North Carolina’s agriculture department used money from an unrelated pollution settlement to start the Hemlock Restoration Initiative last year. The initiative has paid for Lari releases on state lands and this year will hire a coordinator to work with the public.

Rusty Rhea, a U.S. Forest Service entomologist in Asheville, calls Lari a “major player” in saving the hemlocks.

“Trees that looked bad five or six years ago are starting to come back,” he said, as the beetles spread. The service still uses chemicals to treat trees, as a short-term measure, but hopes to rely increasingly on beetles.

Rhea is cautious about declaring the beetle a hemlock savior. It will take years of observation, he says, to gauge Lari’s real impact.

With so many trees already lost, his hope for the hemlocks is modest: To maintain it on the landscape and restore trees where they’ve been lost. “If we could save a third of them, I’d be happy,” he said.

10,000 beetles a year

Dead hemlocks stand shoulder-to-shoulder with surviving trees on Hemlock Hill, a Lees-McRae College property in Banner Elk.

“If it weren’t for the beetles, these would all be dead,” McDonald said. Instead, he said, many hemlocks show up to five years of new growth.

It was here, in 2003, that McDonald first released 300 beetles beside the Elk River. Each beetle lays 200 to 400 eggs, and each emerging larva will gobble about 235 adelgid eggs.

Releasing dozens of beetles at a time, he said, is “like dropping a bomb.” The bugs disperse, following their adelgid food source.

The beetles have expanded their range by 2 miles to 5 miles a year, McDonald says, and have become established in 18 sites from northwestern to southwestern North Carolina.

The Forest Service also released Lari in 2003, near Mount Mitchell and near Asheville, and the beetle has been used in other states. But McDonald says the federal agency, to which he has supplied beetles, was slow to see their worth.

“Those guys didn’t believe what we said until our trees stopped dying,” he said.

Grandfather Golf & Country Club, where the adelgid had been spotted in 2001, was willing to bet on Lari. A $25,000 contract it gave McDonald financed a two-week beetle collecting trip to Seattle.

Course superintendent Gerdon went with McDonald and came back a believer.

The adelgid’s cottony white egg sacs so covered hemlocks in the Northwest that “they looked like they had snow on them,” Gerdon said. But the voracious beetles kept the trees in perfect trim.

McDonald started shipping home 10,000 Lari beetles a year and now sells them for $5 each. Collecting the beetles and releasing them among infested hemlocks is now much of his business.

The country club, meanwhile, saved $100,000 a year when it stopped chemically treating its hemlocks and switched to beetles.

“Anything we can do that is environmentally sound is a good thing,” Gerdon said. “And being able to control a pest without doing anything else about it is nice.”

Beyond the groomed course, within a 35-mile ring by McDonald’s estimate, a battle rages. Invaders seek succulent needles, and beetles pursue their prey.

Henderson: 704-358-5051;

Twitter: @bhender

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