NOTICE: The New York State Department of Environmental Conservation (DEC) announced on August 11, 2020, the confirmation of an infestation of the hemlock woolly adelgid (HWA) on Forest Preserve lands in the town of Dresden in Washington County. This comes just one week after their confirmation of the emerald ash borer (EAB) in Warren County, on the Schroon River in the town of Chester. >Read the LGLC’s statement following these discoveries.  On October 7, HWA was confirmed on Dome Island by a team that included LGLC staff. Ground surveys are ongoing.


Invasive species can have a significant impact on a native ecosystem. The LGLC is actively working to monitor and manage terrestrial invasive plants and insects that are established and negatively impacting our forests and shorelines, or are not here yet but expected to infest the Lake George watershed in the near future.

What are invasive species?

Invasive species are plants, animals, and other organisms either accidentally or intentionally introduced from outside their historic range that cause harm to the environment, economy, or human health. In recent years, the rate and risk of invasive species introductions has been exacerbated due to increased movement of people and materials and increased environmental degradation. Due to the lack of natural predators in their new environment and high reproductive ability, invasives can quickly become widespread and out-compete native species.

What invasives do the LGLC manage in the Lake George watershed?

LGLC staff monitor hemlocks for HWA

LGLC staff monitor hemlocks for HWA

The LGLC has been monitoring and managing terrestrial invasive plants throughout the watershed for more than a decade. There are many invasive plants well established here, but we focus our efforts on a handful that present especially significant risks to the surrounding habitat and water quality: shrubby honeysuckle, garlic mustard, purple loosestrife, phragmites, and Japanese knotweed.

When identified on protected land, either owned by the LGLC or in cooperation with an easement owner or other partner, these invasives are managed through hand removal, cutting, or in some cases, use of carefully applied herbicide. For an example of a successful phragmites management project on an easement property, see pages 18-19 of our 2018 fall/winter newsletter.

In addition to plants, the LGLC is working with our partners to plan for the arrival of the hemlock woolly adelgid, an invasive insect that can decimate eastern hemlock forests.

Hemlock Woolly Adelgid

What is the hemlock woolly adelgid?

The hemlock woolly adelgid (HWA) is an invasive forest pest that was introduced to North America from Japan. They are tiny, aphid-like insects that attach to hemlock trees and suck the moisture and nutrients from the base of the tree’s needles. HWA does not have any natural predators in the eastern U.S., and our hemlocks do not have a natural resistence to infestations.

Why does it matter to Lake George?

The eastern hemlock, Tsuga canadensis, makes up an estimated 60% of total tree cover in the Lake George watershed. Commonly found along streams, hemlock roots stabilize streambanks, preventing erosion and drastically reducing the amount of sediment and excess nutrients that enter the lake.

Eastern hemlocks also provide food and habitat to many animals in the northeast. Brook trout depend on the cool water temperature that is maintained by dense hemlock cover. Chickadees, wrens, warblers, and other songbirds rely on hemlock for habitat. White-tailed deer, snowshoe hare and porcupines feed on its bark and needles.

Without the eastern hemlock, the water quality of Lake George, and the forest habitat of the watershed, would suffer.

What do they look like?

An eastern hemlock can be most easily identified by its needles. They are flat with round tips, and have two distinct white lines on the needle’s underside.

HWA is very small and is most easily identified during the winter months when its eggs appear on hemlock twigs as “woolly” masses.

Picture the underside of hemlock needles

Eastern hemlock needles have two white lines. Photo credit: Pennsylvania Department of Conservation and Natural Resources-Forestry,

HWA egg "woolly" masses

The “woolly” egg masses of HWA on an eastern hemlock branch. Photo credit: Chris Evans, The University of Georgia,

What is the LGLC doing about HWA?


With special infrared mapping, the LGLC has identified locations of hemlocks within the watershed believed to be most at-risk and critical to monitor and protect.


On-the-ground monitoring is the most effective way to detect HWA infestations. Each year LGLC staff and volunteers walk more than 75 miles on protected lands within the watershed to check for signs of HWA.

Following the confirmed infestation of HWA within the watershed in 2020, the LGLC worked with partner organizations (APIPP, Capital Mohawk PRISM, and DEC) to identify and monitor priority hemlocks throughout the watershed. In addition to monitoring our own preserves, we surveyed hemlocks on partner-owned public lands as well as several ecologically important private properties.


Trained staff will treat infestations if found on LGLC land, and provide assistance to partners if HWA is found on other properties.


The LGLC has hosted trainings at our office and in partnership with other groups, for hemlock and HWA ID, monitoring, and reporting.

What You Can Do

Attend a Training

If you are interested in learning more about HWA, please contact the LGLC or check back here to see if we have any upcoming informational sessions. Knowledge is power!

Monitor for HWA

You can look for infestations while you are out in the woods, or even in your front lawn. It only takes a few seconds to check the underside of a hemlock twig—but this short exercise could make a huge impact in protecting the health of our watershed.

Report your Findings

If you suspect that a tree is infested with HWA, please take a photo of the and email it to Monica at with a note of its location.