Damaging bugs threaten to assault and kill Japanese hemlocks in Western Pa.


An nasty tiny insect sucks life from the state tree, the eastern hemlock, and encounters iconic trees at the Flight 93 crash site, Cook Forest, Fallingwater, and one of the wildest landscapes near Pittsburgh – the Buffalo Valley watershed in Buffalo Township .

Known as the woolly Adelgid, this invasive beetle from Asia is about the size of a peppercorn. But its egg sacs are clearly visible and look like tiny tufts of cotton on the underside of the hemlock branches.

If left untreated, many hemlocks in the area will face the death penalty over the next three to ten years, said Timothy Tomon, a specialist with the Pennsylvania Department of Conservation and Natural Resources who focuses on the woolly Adelgid.

It was first identified in Pennsylvania in 1973 and in Westmoreland County in 2006.

Adelgide’s population exploded in the region last year, particularly in Butler and Allegheny counties.

In the past two decades, the invasive insect has been detected in all but three counties (Crawford, Mercer and Greene).

“After all, we have to prioritize what will be treated,” said Tomon. “We’re trying to focus on the parks and forests that are known for their hemlocks.”

The first to go

The first victims will be the older trees and trees that grow on rocks – both are more stressed and cannot tolerate the attack, Tomon said.

Pointing to Charles Bier, standing next to a bank of hemlocks impossibly perched on the rocks in a deep river valley in Buffalo Township, said, “These will likely go.”

Bier, Senior Director of Conservation Science at the Western Pennsylvania Conservancy, discovered the woolen Adelgid a few years ago on his property near the Todd Nature Reserve and the Butler-Freeport Community Trail.

“I am alarmed and have been waiting for it,” said Bier, who has seen the devastation in the eastern and central part of the state for the past 20 years.

Almost all of the native evergreen trees in southwestern Pennsylvania are eastern hemlocks. The trees are distinctive and valued, especially in winter, and offer the only green in an otherwise brown, withered landscape.

“This has a big impact on the Pennsylvanians, who have a sense of the native landscape,” Bier said.

It is a poetic injustice in Buffalo Township, where territories are being preserved by the Audubon Society of Western Pennsylvania for the unique habitat that hemlocks provide.

Audubon treats various hemlocks in Buffalo Township with the help of the State Department of Conservation and Natural Resources.

But some will not be helped and will likely die, said Bier. The Adelgid is visible on nearby hemlocks along the Buffalo Freeport Trail.

Considering the loss of many stocks of native hemlocks, Bier said, “This will be a slow burn.”

How bad is it?

The effects are bad, say experts.

“The trees on the rocks that everyone at McConnells Mill State Park wants to see will be gone in four years,” said Tomon.

State officials are trying to reduce the damage.

“We see the woolly Adelgid everywhere,” said Tomon. Penn State Cooperative Extension in Allegheny County reports that this year it was inundated with phone calls from residents who have the woolly Adelgid on their hemlocks and want to save their trees.

There is no way to exterminate the woolly Adelgid.

“We can only try to manage the trees and suppress the Adelgid numbers so the trees can survive,” said Tomon.

In terms of the number of trees lost, the Adelgid threat isn’t as devastating as American chestnut rot or Dutch elm disease in the state, he said. However, once you kill the hemlocks, move on to other life forms.

The hemlock is more than a tree.

It’s a key species that plays a unique and important role in creating a habitat for wildlife, said Donald Eggen, forest health manager for the Pennsylvania Department of Conservation and Natural Resources.

“If you lose the hemlocks, you lose the fish, birds, insects, fungi, microbes, plants, and some mammals associated with this hemlock habitat – a combination of shade, soil, and water chemistry,” Eggen said.

Hemlock-lined canyons, known for their shade and cool waters, provide habitat for native trout.

Treatment only, no cure

The main treatment for forest and iconic hemlock locations is an insecticide that is injected into the soil around the trees. This lengthy process may not work realistically with large stands of trees, especially on inaccessible steep hills.

The best hope is the release of bugs and insects that will eat the adelgid. But it takes years for their populations to grow large enough to eat enough Adelgid to keep them in check. The beetles are carefully selected predators that are only specific to the Adelgid and do not get anywhere else in the environment, according to experts.

Aggressive treatment programs are running in the area at the Western Pennsylvania Conservancy’s Fallingwater Historic Site and Bear Run Conservation Area in the Laurel Highlands.

The Department of Conservation and Natural Resources is treating woolen adelgid hemlocks in McConnell Mills, Erie Bluffs, Cook Forest, Ohiopyle, and other parks and state forests. On site, the department has released predatory beetles to eat the Adelgid in Sewickley Heights Borough Park and Fall Run Park in Shaler.

The National Park Service just signed a new contract to continue its Adelgid control program on the Witness Trees, a series of hemlocks that Flight 93 hit when it crashed into a field during the 9/11 attacks in Shanksville.

Flight 93 National Memorial launched a program to suppress the Adelgids in 2013. Over the next three years, workers will treat old trees and saplings and saplings across the 11-acre hemlock grove at the crash site, the National Park Service said.

The hemlock witness trees will be treated through a combination of soil injection, basal treatment, trunk injection, application of horticultural oil and introduction of predatory beetles, said Katherine Hostetler, spokeswoman for the Flight 93 memorial.

“Although the Adelgid will forever change the hemlock grove at Flight 93 National Memorial, with continued funding, dedicated staff, and dedicated partners, the hemlock witness trees will remain for generations to come to know what happens here on September 11, 2001 is, “she said.

There is reason to be hopeful. The beetles, along with experiments with other predatory insects, could become more effective in the coming years, Tomon said. And some cold winters can hit the adelgide population and slow them down, he added.

Pennsylvania has the resources and the manpower to fight, he said.

“We have a large staff and more money than other countries. We were connected to forest groups working on the same issues, ”said Tomon.

Beer is hopeful. Hemlocks that are genetically resistant to the Adelgid are out there. Treating hemlocks with bugs and insects will likely make a difference, even if it takes years.

“The preservation started so early,” said Bier.

The nonprofit used insecticides on the trees surrounding the historic Fallingwater house and the nearby countryside. They built “insects” for the beetle population to eat the Adelgid in Bear Run and Wolf Creek Narrows near Slippery Rock.

“We tried to save some of the trees in the Bear Run watershed, but there are thousands and thousands of hemlocks on this property – about 5,000 acres,” he said. “You can’t really treat every tree.”

Mary Ann Thomas is a contributor to Tribune Review. You can contact Mary at 724-226-4691, mthomas@triblive.com, or on Twitter.