Cook Forest giants
Efforts underway to protect hemlock trees from invasive bugs
Cook Forest State Park is home to the biggest hemlock trees in the eastern United States. The tallest trees reach almost 148 feet, a rare occurrence on this side of the country due to extensive timber cutting. Now these giants of the forest face a tougher foe: invasive bugs that are decimating trees across the East Coast.
Most years, many people come to see Mohawk and Seneca hemlock trees in this 8,500-acre park that stretches through Clarion, Forest and Jefferson counties. But the trails haven’t seen many visitors lately due to COVID-19 restrictions, according to Dale Luthringer, Cook Forest environmental education director. About 15 visitors joined Mr. Luthringer for a tour July 18.
Hemlocks are native trees found from Georgia all the way to Canada. They also grow in the western states but are much taller and wider. Yet Mr. Luth- ringer maintains that Cook Forest’s hemlocks are special; they are the legacy of conservation efforts by Anthony Wayne Cook in the 19th century.
“The best stand of tall hemlocks in the eastern United States,” he said confidently.
He estimates there are hundreds of thousands of hemlock trees here, but he tries to show visitors the tallest ones up close. It’s difficult to tell their actual height because the view is blocked by smaller trees. You have to strain your neck at just the right angle to see the very top.
Hemlock woolly adelgids were first discovered in Virginia in the 1950s, but they weren’t seen as a threat until the 1990s when they decimated hemlocks in the Smoky Mountains of North Carolina and Tennessee.
“There’s thousands, hundreds of thousands of them on each tree,” Mr. Luthringer said. “They defoliate the tree year after year after year.”
Cook Forest has been
infested since 2013; Mr. Luthringer discovered the bug while preparing for a conference to discuss invasive species.
“Right before this huge conference with all these agencies who are supposed to decide what we’re gonna do when [HWA] gets here, it’s here.”
Adelgids typically begin feeding at the base of a tree’s needles. Mr. Luthringer said he knew the species had invaded Cook Forest when he spotted waste that looks like snowballs. It often takes up to three years to know if a tree has been attacked since the bug is so small, nearly invisible to the human eye. It’s almost impossible to get rid of hemlock woolly adelgids once they’ve settled in, he said.
His other concern is another bug, the elongate
hemlock scale. He believes it’s coming soon and will compound damage caused by the woolly adelgid.
“It seems like it’s slower moving, but it’s like another wave that’s coming and that’s … usually the death note.”
He said it’s most likely already in Black Moshannon Park in Centre County. “I hope it doesn’t get here.”
To keep hemlocks healthy, Cook Forest park staff are treating most trees with a chemical that is inserted at the base and can take up to two years to make its way up the entire trunk. No further treatment is needed for seven or eight years, Mr. Luthringer said.
“That’s all we’re doing is giving the forest time. It’s a Band-Aid for seven, eight years down the road.
Hopefully we get another solution.”
A biological treatment may be the only way to keep the bug in check, according to Mr. Luthringer. Park staff occasionally use a beetle native to California that eats the pest. Cold winters will kill 90% of adelgids as well, but it’s never cold enough to kill them all.
Until now, Cook Forest has been lucky and its tallest hemlocks remain healthy. On guided hikes, Mr. Luthringer talks of exploring “600 years of forest history.” He stops visitors at three trees in particular due to their massive size. The hemlocks range from 134 feet to nearly 148 feet in height and 12-13 feet in width. It’s estimated the trees are anywhere from 250 to 350 years old.
Halfway through the tour, visitors had the opportunity to see a hemlock that had fallen nearly a week earlier. Its trunk showed just how large the hemlock had been. Robert Norcross, 8, of Sharon gathered some sawdust and bark from the fallen giant. He was on a family vacation with his parents, Jeremy and Jessica, and his 2-year-old brother, Lenox. When asked what he enjoyed most about the hike, he said, “Everything!”
While Cook Forest State Park has lost some hemlocks to the woolly adelgid, staff are working hard to ensure visitors like the Norcross family can continue to enjoy the trees for years to come.