New invasive threat

Seen here is a picture on the state Department of Environmental Conservation’s website of the hemlock woolly adelgid, HWA, an invasive species that has been working its way north in New York state since the mid-1980s. The species harms hemlock trees, which can contribute to soil erosion and degraded water quality.

Chris Evans, The University of Georgia

LAKE GEORGE — A new invasive species is on the doorstep of Lake George, and may already be here, which could threaten the water quality for local lakes and streams.

Environmentalists are worried about hemlock woolly adelgid, or HWA for short. The aphid-like insect only attacks hemlocks. It was introduced from Japan sometime in the 1950s and first found in Virginia, according to Warren Rosenthal, conservation manager for the Lake George Land Conservancy.

“It’s been spreading up and down the East Coast for decades,” he said.

The invasive species was discovered in New York in 1985 in the lower Hudson Valley and Long Island, according to the state Department of Environmental Conservation.

The insect has killed almost all the hemlock in the Great Smoky Mountains and West Virginia. It has been found as far north as Schenectady, according to Rosenthal.

“It usually kills hemlock within 5 to 10 years, depending on the health of the tree,” he said.

Rosenthal said the Lake George Land Conservancy has been trying to build awareness of the problem. It is particularly concerning because the Lake George has one of the largest concentrations of hemlock.

“If they were to die, particularly in large numbers, it would have a very negative impact, most likely, on water quality for many streams and lakes,” he said.

Hemlock can be found along many of the streams that feed into Lake George, according to Rosenthal.

“The hemlocks are basically holding the soil together, keeping it from eroding, keeping the temperature down significantly,” he said.

A cooler temperature is necessary for species such as trout to survive and that could affect the entire ecosystem, Rosenthal said.

Damage to the hemlock ecosystem can also affect moose, black bears, salamanders and migrating birds, as well as lichen and plants, according to the state Department of Environmental Conservation website.

Rosenthal said there could also be an economic impact as Finch Paper uses a lot of hemlock in their manufacturing of paper.

Juvenile HWA look to attach themselves to a host tree at the base of the needles. They insert their long mouthparts and feed on the tree’s starches, according to the DEC. They stay in that same spot their entire lives.

To spot HWA, Rosenthal said people should look for white fuzzy balls on the underside of branches.

“It’s relatively easy to identify if you see it,” he said.

Among the other signs of infestation are loss of needles, branch dieback and gray-tinted foliage, according to the DEC.

People who believe they have spotted HWA are asked to take pictures, note the location and contact DEC Forest Health at 1-866-640-0652 or online at iMapInvasives at

Rosenthal said the long-term solution is producing a type of beetle that will eat the HWA.

“The problem is that you have to produce it in a laboratory and then ramp up the production level where you can produce enough of the predators,” he said.

“But that’s going to take five years, maybe longer, to get to that point,” he added.

In the meantime, Rosenthal said there should be teams on the grounds doing monitoring and early detection.

“It’s been proven that if you detect an early outbreak, you can stop it,” he said.

The solution is to apply a couple of insecticides directly to the tree bark. Rosenthal said the Lake George Land Conservancy has asked the DEC if it would take the same approach to an area of northern Saratoga County up to the Great Sacandaga Lake and east to the southern Lake George basin. Rosenthal said the HWA could already be here.

“It’s somewhat of a needle-and-haystack scenario. Obviously the more eyes on the ground you have looking, the better the chances,” he said.

The Adirondack Mountain Club has had a volunteer forest pest identification program for a few years, according to Rosenthal.

“There’s no substitute for professionals on the ground full time,” he said.

One issue is there are restrictions on what can be done on forest preserve land in the Adirondack Park, Rosenthal said.

Some of the highest concentrations can be found in Moreau Lake State Park, along the Great Sacandaga Lake and along West Brook in Lake George, according to Rosenthal. The Lake George Land Conservancy is trying to figure out how it can map some of the largest concentrations of hemlock.

Rosenthal said people can get what he calls “invasive species fatigue” trying to fight all these predators. However, in this case, something can be done about the problem — unlike the emerald ash bore, which is likely to wipe out every ash tree in the United States.

“If you put enough resources into it, I think we can stop it from getting into the park,” he said.

You can read Michael Goot’s blog “A Time to Learn” at or his updates on Twitter @ps_education.



Reporter for The Post-Star, covering the city of Glens Falls, town and village of Lake George and northern Warren County communities.

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