The trees of Cook Forest State Park survived the clear-cutting of Pennsylvania more than a hundred years ago. Now the virgin old-growth hemlocks in the park are threatened by a pest that has plagued trees from New England to Georgia. This spring, WPSU’s Emily Reddy tagged along with a group headed out into the forest to save the hemlocks.
The pest in question is the Hemlock Woolly Adelgid. It’s common in much of Pennsylvania. But this is the first time it’s been found in this park, which has some of the oldest and largest hemlocks in the state.
“OK, do we have everybody back?... OK, Sean, Dale, one trainee, two trainees…”
Other than Rachel Wagoner, who’s organized today’s outing, it’s all men in khaki and olive green. They’re gathered outside the park rangers’ office. Most work here at Cook Forest, but some are from other state parks offices, and a couple – like Wagoner – work for Pennsylvania’s Department of Conservation and Natural Resources in Harrisburg.
Today’s treatments have drawn a lot of participants because they’re testing out a modified treatment method. Instead of injecting insecticide into the ground around the trees, they’ll spray it onto the trunks. That’s because the soil here is so rocky. Wagoner helped custom-build the spray-packs that some men in the group are wearing.
“So, we’re going to grab these backpack sprayers and Dale is going to lead us into the area that ...it was the first area where the adelgid was identified at this park. And where some of the most significant trees in the area have been identified and flagged already,” Wagoner said.
Dale Luthringer takes the lead and guides the group into the forest.
“Alright, let’s work our way over to where we’ll start up the trail here,” Luthringer said.
They’re heading to the Seneca forest, which is named after one particular tree -- the Seneca Hemlock. Luthringer is an expert in old-growth trees like this one, which is around 300 years old. He leads the group about half a mile into an area of woods that has never been cut for timber. He gathers everyone in front of several very tall evergreens.
“Right here, this one tree that we’re pointing at you can see a little yellow tape at the bottom, we call that the Seneca Hemlock, and right now it’s the tallest known hemlock in the Northeast,” Luthringer said.
Wagoner assigns trees and the men get to work circling the massive hemlocks and spraying them up and down.
At over 147 feet tall, the Seneca is also the third tallest hemlock north of the Smoky Mountains. And the hemlocks at Cook Forest hold another, more dubious, distinction. They mark the first time Hemlock Woolly Adelgid has been found on the Allegheny Front. The bug has been found in 56 of Pennsylvania’s 67 counties. Wagoner had hoped the higher altitude on the Front might stymy the adelgids, but here they are. She holds out a small branch with bits of white fuzz to prove it.
“So, this is where it gets its name from,” Wagoner said. “This is a hemlock and that’s kind of woolly looking and inside there’s an adelgid. Hemlock Woolly Adelgid. This is what they overwinter in. The crawlers are still inside there.”
Now that warm weather is here, they’re crawling out of their woolly houses to feed on the trees.
“What they do is they insert their stylus mouthparts right at the base of that needle and the twig and that’s where they suck the juices. That’s where they feed,” explained Don Eggen. Eggen is in charge of forest pest management for the bureau of forestry.
An infested tree can turn greyish-green, lose its needles, and eventually die. Hemlock Woolly Adelgid can kill a hemlock in Pennsylvania in less than ten years. Trees in the southern Appalachians are being killed off even faster. A study by the US Forest Service said the pest has the potential to kill most of the region's hemlock trees within the next decade.
Eggen said we need to save the hemlocks because they’re environmentally important as a “foundation species.”
“If these hemlocks were not here this habitat would be completely different,” Eggen said. “Every single thing you see here, the undergrowth, the soil, the birds, the invertebrates, everything else including the stream. Trout fishermen love hemlock because that’s where trout occur. And we have world-class trout fishing in Pennsylvania. It effects those waters. The chemistry of that stream will change if you don’t have hemlocks.”
Eggen says the Bureau of Forestry is developing a hemlock conservation plan. It will include information about hemlocks and the pests that attack them, and strategies for treatment. In addition to pesticides, Eggen said they release beetles that eat Hemlock Woolly Adelgid. But cold winters often kill the beetles, so they’re testing hardier species in the lab.
They’re also studying hemlocks that seem to have a natural resistance.
“As a matter of fact they have found, we call it the ‘bullet-proof’ stand of hemlock,” Eggen said, “and it’s…I mean all the hemlock around it are dead and this stand is still alive and they’ve been testing it. They’ve been trying to get Hemlock Woolly Adelgid established on it. So we want to look at the genetics of this. So between looking at host resistance and maybe breeding, along with preditors, that’s the long-term solution.”
For now, they’ll use the pesticides to treat trees in Cook Forest covering a 78-acre area. They’ve also budgeted for 20 more acres, figuring they’ll find more adelgids at some point later this year. And treatment isn’t cheap. Just the insecticides for those treatments could cost $40,000-$50,000.
Today they treat 24 trees in their test run before Luthringer leads them back to the ranger’s station.
“There’s a lot of work to be done, but this is huge,” Luthringer said. “To have some of the top folks in the state here today really says a lot, you and uh, we’re very thankful.”
Back at the ranger’s station, assistant park manager Sean Benson is putting away equipment. He says these iconic trees bring more than 300-thousand visitors to the park every year.
“So we’re faced with an uphill battle to protect something that is very very important to us,” Benson said.
