6 News caught up with a crew in the Cosby Conservation area of the park recently. Forester Jesse Webster lead a trek to treat trees about a half mile back from the trail head.
Webster pointed out healthy hemlock stands with plush green canopies, and other barren looking stands where all the needles have fallen off the trees.
The park service says nearly 1500 acres of old growth hemlock have been mapped with some trees that are more than 500-years-old, six feet across and 160 feet tall.
Webster says about one third of the hemlocks in the national park are being destroyed by the invasive adelgid.
"We're hoping to outride the adelgid wave. What we've seen is an explosion in the population. We've treated roughly 120,000 trees," Webster says.
The hemlock adelgid was first noted in the park in 2002, and can kill a tree in just two years.
Outside of the hemlcocks' beauty, often referred to as the redwoods of the East, the hemlocks are also a crucial part of the park's ecosystems.
"We 're losing those unique habitats we have in the park," Webster says.
6 News was with the crew for about five hours as they treated the trees with a chemical compound at the base that will transpire through the tree needles.
Webster says in the simplest terms, it works like a dog's flea and tick treatment. "It's similar to the treatment behind their shoulder blades and it's the same active ingredient."
They also attack the problem on this day with more than 1,800 microscopic beetles that feed off the hemlock adelgid.
The beetles were bred at the University of Tennessee and once placed in the park, the beetles will eventually fly up, making their way into the taller, old growth trees.
The method is slow to show results, but so far, everything combined is proving to be effective,
"If we hadn't done anything, 99.9 percent of these trees would be dead in 10 years," Webster says.
So far, the park service has spent nearly $4 million fighting the woolly adelgid, but officials say that's cheaper than removing all the dead trees. They also say it's a safety issue since many are near roads and campgrounds.
Also, just recently released reports show trees in the areas of the beetle releases are having a 75 percent recovery rate.