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.

Bushy, green Japanese knotweed fills in the banks of a stream. A guardrail is bordering the stream on the right.

Together, the LGLC and our partners—including the New York State (NYS) Department of Environmental Conservation (DEC), Adirondack Park Invasive Plant Program (APIPP) and other members of the NYS Partnerships for Regional Invasive Species Management (PRISMs), NYS Hemlock Initiative, Adirondack Mountain Club, and iMapInvasives—are leading the charge in invasive species research, education, monitoring and management.

A group of people wearing reflective safety gear are talking and surrounded by green trees.

What is the LGLC Doing to Manage Invasives?

The LGLC has been monitoring and managing terrestrial invasive plants throughout the watershed for more than two decades. 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.

In addition to plants, the LGLC is working with our partners to manage invasive pests, particularly the hemlock woolly adelgid, an invasive insect that can decimate eastern hemlock forests. (See below for more about this pest.)

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 THE HEMLOCK WOOLLY ADELGID 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 does HWA 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.



With special infrared mapping, the LGLC has identified locations of priority hemlocks on LGLC protected lands 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 LGLC’s protected lands within the watershed to check for signs of HWA.

The first widespread infestation of HWA within the watershed was confirmed in 2020. Following that discovery, the LGLC assisted partner organizations (APIPP, Capital Mohawk PRISM, and DEC) with delineating and treating hemlocks on NYS DEC lands. In addition to assisting with HWA treatment on NYS DEC lands, we have joined partners at The Nature Conservancy (TNC) in treating the 15-acre Dome Island Sanctuary on Lake George.

In 2021, the LGLC joined in a state-wide initiative to engage citizens in efforts to monitor for the invasive HWA. As a result of this Adopt-A-Trailhead program, more than 100 trails were monitored regionally by nearly 400 citizen scientists, all of whom went through training for HWA identification and how to report their findings with iMapInvasives (see below for more info on how to join this effort).


The LGLC’s trained staff have assisted with the treatment of over 30 acres of infested hemlocks on Dome Island, Shelving Rock and Paradise Bay.

In spring of 2023, HWA was found on LGLC’s Clark Hollow Bay property in the Town of Putnam. Under the guidance of the New York State Hemlock Initiative, NYS Regional PRISMs, and forest health professionals, the LGLC developed a strategy for long-term management of HWA at the site. In accordance with the HWA Management Plan for the property, chemical treatment at Clark Hollow Bay began in fall of 2023.

Each year, up to 256 diameter inches can be treated per square acre. As of October 2023, a total of 3,929 diameter inches have been treated with an imidacloprid-based insecticide. Within a year of Imidacloprid-based treatment, trees are protected from HWA for up to seven years of efficacy.

LGLC staff released 2,000 Laricobius nigrinus beetles in early winter, 2023, and Leucotaraxis silver flies in spring of 2024. These releases are part of an effort to establish hemlock woolly adelgid (HWA) biological control (bio-control) on the property, which is part of a long-term management plan.

The goal of using a chemical and bio-control two-prong approach is to provide chemical protection to the trees while the bio-controls have time to build numbers and establish populations large enough to keep the HWA population down through natural predation.

Laricobius beetles are native to the Pacific Northwest, and are specialist predators, feeding exclusively on HWA throughout the fall and winter when HWA is in its adult form. Silver flies are natural predators of HWA on the U.S. west coast. They are released in the spring and feed on HWA during their egg-laying season. Because the Laricobius beetles and silver flies target different HWA life stages, they can more effectively reduce the reproduction of HWA when established together.

Though these bio-controls have been released at other protected lands in the Lake George watershed, this release is the first on LGLC-owned land, and the site is the northern most known HWA infestation. The LGLC will continue working with the NY Hemlock Initiative to monitor and manage the site. Visit the Hemlock Initiative’s site for more information about their research.

Other Invasives and Resources

Emerald Ash Borer

Emerald ash borer (EAB) is an Asian wood-boring beetle that feeds on ash trees (Fraxinus spp). Adults are approximately ½ inch (1.2cm) long with a metallic green body and copper segments beneath their wings. EAB is spread long distances through infested firewood or wood packaging material, but is also an efficient self-disperser, capable of traveling up to seven miles in a single flight. Larvae feed on the inner bark of ash trees, disrupting the tree’s ability to translocate nutrients. Trees infested with EAB may have a thinning crown, bark splits, heavy bark loss from woodpecker feeding, and/or D-shaped exit holes.

Once established, eradication of EAB is not possible. Reducing the transport of infested ash nursery stock, firewood, unprocessed ash logs, and other ash products can slow the spread. Insecticide can be used to save ornamental or street trees but is not viable for treating at a landscape level. Biological controls are being explored. Prevent the spread of EAB by not moving untreated firewood, buy firewood local to where you will burn it, or purchase heat treated firewood. 

APIPP has established plots on ash tree stands throughout the Adirondack Park in order to monitor for EAB.

One such plot is a stand of black ash at the LGLC’s Sucker Brook Preserve in Putnam. Black ash trees are rare in the Adirondacks, so this plot offers an important study group to the project. LGLC staff worked with APIPP to inspect the black ash stand and tag the trees for annual monitoring.

Beech Leaf Disease

Beech Leaf Disease (BLD) kills both native and ornamental beech tree species, which is cause for concern since beech trees are prevalent in Adirondack forests. BLD was first identified in Ohio in 2012 and much about it, including the full cause of it and how it spreads, is still unknown. The disease is believed to be associated with a nematode, Litylenchus crenatae mccannii, but scientists have a lot to learn and data collection is an essential part of the process. The telltale banding between leaf veins, as well as browning and curling of leaves caused by BLD, is best observed from early summer to fall.

BLD was confirmed in the town of Bolton in summer of 2023, the first confirmed occurrence of this invasive forest pest in Warren County. The first confirmed case of BLD in the Adirondacks was in Herkimer County in 2022. It was first confirmed in the U.S. in 2012, and it is sweeping its way rapidly through infected areas. Click here to read APIPP’s recent press release about BLD.

APIPP launched its BLD Forest Pest Hunters volunteer program on August 2. Click here to watch the webinar recording. Click here to learn how to sign up to survey a trail. If you have questions, please reach out to Becca Bernacki, APIPP’s Terrestrial Invasive Species Coordinator (rebecca.bernacki@tnc.org).

Adirondack Park Invasive Plant Program: APIPP

The Adirondack Park Invasive Plant Program (APIPP) serves as the Adirondack Partnership for Regional Invasive Species Management (PRISM), one of eight partnerships across New York. The LGLC and APIPP work together on invasive species management, research, and outreach to help protected and manage the lands of the Lake George watershed.

APIPP is a partnership program founded in 1998 by The Nature Conservancy, New York State Department of Environmental Conservation (NYSDEC), New York State Department of Transportation and New York State Adirondack Park Agency, and it is housed under the Adirondack Chapter of The Nature Conservancy. Funding is provided via five-year contracts from the New York State Environmental Protection Fund as administered by NYSDEC. Since APIPP’s founding, the program has grown to include more than 30 partner organizations and hundreds of volunteers.

NYS Hemlock Initiative

The New York State Hemlock Initiative (NYSHI) is a Cornell University project that researches biological control solutions for hemlock woolly adelgid (HWA), and works with scientists, natural resources professionals, and New York residents that are united in their love for hemlock trees and dedication to hemlock conservation.

The LGLC has been working with NYSHI and its director, Dr. Mark Whitmore, for many years, gaining invaluable knowledge and resources to help us manage the lands of the Lake George watershed.

What Can I Do?

Attend a training or volunteer work day

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

You may also join a volunteer work day focused on managing invasives around the Lake George watershed. These group events are led by LGLC staff at various properties. Any scheduled events would be posted on our Volunteer page.

A group of young women posing in a large forest and holding tools to cut and clear branches.

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. If you suspect that a tree is infested with HWA, please take a photo of the and email it to Monica at mdore@lglc.org with a note of its location. Or, you can create an account in iMapInvasives to submit your finding directly:

A group of people wearing reflective safety gear are inspecting tree branches.
  1. Download the app to your device
  2. Visual step-by-step instructions on how to set up your iMap Account and start Collecting Data available online
  3. Visit the iMapInvasives website to set up your account
  4. Confirm your account using the email sent to the address you register with
  5. When setting your preferences, set your jurisdiction to “New York,” and find the Project: “APIPP VOLUNTEER FOREST PEST MONITORING (Project ID Number: 1108)”
  6. Grow comfortable using iMapInvasives using online self-guided trainings
Two phones are displaying the iMapInvasives application. The phone on the left has the iMpaInvsaives logo and the one on the right has the user interface.
Our partner in invasives management, the Adirondack Park Invasive Plant Program (APIPP) is a great resource for information on many invasive plants and animals within the Adirondack Park and New York State. Visit their website for searchable databases of terrestrial and aquatic invasives, downloadable info sheets, and training events planned throughout the year.
About Us

Protecting the land that protects the lake since 1988. The Lake George Land Conservancy is an accredited not-for-profit land trust dedicated to working with willing landowners and other partners to protect the world-renowned water quality of Lake George and to permanently preserve the natural, scenic, historical and recreational resources of the Lake George Region.

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