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Stop the Spread

Knowledge is Power. Educate yourself and others, so together we can have a positive impact on the livelihood  and longevity of our region. 
Stop the Spread Top

Invasive Species

We Need Your Help!

DANGER, CAUTION and WATCH…these are the three warning levels we’ve assigned to the invasive species threatening the Schroon Lake Watershed. These “unwanted hitchhikers” threaten the lake we love, our home properties and our surrounding lands.


Invasives are non-native plants, animals or insects that cause harm to the environment and/or people’s health. The types of invasives creeping into the Adirondacks is rapidly increasing, and along with it, their proliferation and destructive wake. One of the biggest threats to our watershed is the Hemlock Woolly Adelgid. If not controlled, most of our region’s hemlocks will be destroyed within 10 years!


Invasives have no upside and numerous downsides:

  • Drag property values down

  • Impede access to recreational uses of the lake, such as swimming and boating

  • Increase the potential for erosion

  • Adversely affect the cold-water fishery

  • Destroy trees and other plants

Through surveillance, harvesting, boat washing stations and education, ESSLA is striving to protect the Schroon Lake watershed from the spread and negative impact of invasive species. But we can’t do it without you! Whether you’re a resident or visitor, please help us fight this battle. Learn how to identify the various species. Be on the lookout while on the lake, walking, hiking or working on your property. And please contact us at if you spot something!



Aquatic and terrestrial invasives that are already in Schroon Lake’s watershed and have the potential to wreak havoc.

NOTE: HWA has not yet reached our watershed, but poses such a serious threat, we've placed it in the Danger section.

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Bush Honeysuckles

An ornamental woody shrub which grows well in full or partial sun. Leaves are oval, opposite with smooth edges. Grey Stems are hollow. It flowers in May / June with pink, white or yellow blooms followed by clusters of red, pink or orange berries in late summer. Spreads long distances into forests by birds dispersing fruit & seeds.  Six-15’ feet tall and 20+ feet wide, it forms dense thickets, crowding out native plants and inhibiting forest regeneration.


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Eastern Larch Beetle (ELB)

 The Eastern Larch beetle is a bark beetle native to North America. Their main host is the native Eastern Larch tree (also known as Tamarck), a deciduous conifer. Recent reports have found that the beetles are attacking and destroying healthy trees. The Adirondack Park has the highest concentration of Eastern Larch in NYS. Once a stand is infested there can be substantial mortality over the course of several years. The Beetles are about 4 mm (5/32 “) and bore two millimeters (3/32”) holes into tree trunks and branches. 


Aquatic Invasive Species found in Schroon Lake:                                      Euras

Eurasion Milfoil

An underwater perennial grass that can reach heights of 20 feet, forming dense mats near surface. Usually 12-21 leaflet pairs per leaf.  Leaflets are closely spaced.  Leaves collapse around stem when out of water. Reddish stem that branches near surface. Plant fragments easily break off and can be transported from lake to lake via boats and trailers, starting new populations, degrading habitat and reducing recreational access. Once established, it spreads easily, grows quickly and is difficult to remove. The densely growing grass entangles boat propellers, interferes with swimming and fishing and negatively impacts the natural aquatic habitat.  


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Harmful Algal Blooms

Algae found along shore lines or in open water, its blooms often look like thick scum or paint in differing colors on the surface of the water.  They can be found along shore lines or in open water and last anywhere from hours to weeks. HABs can release dangerous toxins that are public health concerns. Avoid swimming, boating, otherwise recreating in or drinking water with a bloom.  In NY, they are increasing in frequency and in Sept. 2020, Schroon had a bloom that was confirmed as a HAB by NYS.



Japanese Knotweed

Introduced into the US from Asia as an ornamental and is now one of the most common invasive plants in the Adirondacks, spreading rapidly along stream banks, rivers, roadsides and woodlands while crowding out and altering the landscape. Its shallow, but extensive root system is ineffective at preventing streambank erosion or stabilizing soils.  Stands are very easy to identify. Stalks are persistent through winter. Heart-shaped or broadly ovate leaves grow in an alternating pattern on the stem and average 6’ in length and 3 – 4’ in width. Colonies are dense and thrive in shade and sun.  Clusters of small greenish white flowers arranged in spikes near the end of the stem bloom in Aug. to Sept. turning to buckwheat-like seeds by early October. It can damage homes and properties with its ability to grown through hard and dense materials (e.g.; cracks in foundations).


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Jumping Worms

 An aggressive Asian earthworm causing major forest ecosystem disturbance by stripping the soil of nutrients, inhibiting plant growth, allowing other invasive species to move in and displacing beneficial European earthworms. Jumping worms can reach six inches and live in leaf litter, organic matter and the top few inches of the soil. When disturbed, they thrash about with an erratic snakelike movement. They have a prominent milky white to light gray band that is flush with and completely encircling its body. European nightcrawlers look similar, but their band is raised and reddish-brown in color. 


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Purple Loostrife

An erect, hardy invasive herbaceous biennial averaging 3-7 feet, preferring open sun and moist soil conditions.  Grows along roadside ditches, marshes, river banks, edges of ponds.  It has five or six petaled magenta flowers arranged close to the stem emerging in July and remaining thru Sept.  Leaves are lance-shaped, typically opposite or whorled with smooth edge.  Stems are square / four sided and rigid.  Spreads quickly by seeds and crowds out native wetland vegetations such as cattails, grasses, sedges and rushes. Impact on native wetland has been disastrous with PL virtually eliminating all other plants and affecting the entire ecosystem.


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Wild Parsnip

An herbaceous biennial/perennial plant from Europe & Asia that thrives in full sun along roadsides & fields, growing 2-5 ft tall with celery-like leaves. It looks similar to Queens Ann Lace, but has yellow flowers. Blooms June thru August with small, five petaled yellow flowers arranged in a flat topped, 2 – 6” broad umbrella. Taproot is long cone-shaped and thick.  DO NOT TOUCH THIS PLANT! Its sap causes a painful and blistering rash that persists for up to 6 months and may require medical attention. The sap contains chemicals which can make skin vulnerable to sunlight / UV radiation.


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Curly Leaf Pondweed

Fully submersed aquatic plant. Has a very distinctive appearance with crinkled leaves resembling wavy lasagna noodles. They are approximately 1/2" wide and 2-3 inches long. The leaves are arranged alternately around the stem and are finely toothed, becoming denser at the end of branches. Plant dies in July and seeds drop to bottom sediment. Forms dense mats that inhibit growth of native species and impede recreational activities.



Emerald Ash Borer

A small beetle that attacks only ash species. Signs of infestation include dieback, thinning, usually starting at canopy top, epicormic shoots from the tree base, woodpecker activity and bark splitting. On the trunk and branches, look for small (1/8 in. diameter) D-shaped holes that are left by emerging beetles.  When the bark splits or falls off, S-shaped larval galleries may be visible. Ash seeds are a food source for bird & mammals. The tree is used for flooring, furniture, lumber and pallet manufacture. Heavily infested trees die within 2-3 years of when symptoms are observed.


Garlic Mustard

Garlic Mustard

A biennial herb averaging 3+ feet that emerges in early spring. It begins as an inconspicuous first year plant (rosette) that looks similar to wild violets having triangular somewhat heart shaped leaves that have coarsely toothed margins and wrinkled leaf surfaces. 2nd year - multiple stems with a tall flower spike and four petal white flowers developing into slender pods bursting with tiny round seeds and sharp-toothed leaves.  Leaves & single stems produce distinctive garlic odor when crushed. A native to Europe, Asia & NW Africa, it invades moist forests, wooded streambanks, roadsides and trail edges where it disrupts normal plant – fungi relationships resulting in elimination of native species. Its roots exude compounds that alter soil chemistry to favor its survival at the expense of other species. Difficult to control once established.  


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Hemlock Woolly Adelgid (HWA)

Tiny insect from Asia that attacks Eastern Hemlock Trees. Appears as white wooly masses clumped on the base of the needles under the outermost branches. Hemlocks are well suited for growing on steep slopes, stabilizing shallow soils and providing erosion control. If HWA is not controlled, vulnerable animal populations are expected to diminish and most of the region’s hemlocks will be killed within the next decade. If you see something suspicious, note the location, take pictures and report it right away by calling the DEC forest pest hotline at 866-640-0642.


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Japanese Barberry

An ornamental bush from Japan which spreads rapidly, forms dense thickets and crowds out native understory plants.  A dense deciduous spiny shrub, 2-8 ft tall with small oval to spoon shaped green, yellow or purple leaves with smooth margins that turn red in fall. It has tiny pale yellow dangling flowers that hang in clusters of 2-4 nodes that bloom in April and May.  Arching branches are grey with sharp thorns. Berries-bright red oval shaped. Grows well in bright sun or shade. Unpalatable for local wildlife, but serves as a deer tick habitat and is implicated in the spread of Lyme Disease.



Oriental Asian Bittersweet

An aggressive perennial woody vine from Asia. It has elliptic alternating leaves with serrated edges, spiraling around a stem. Stems vary in diameter and can be up to 6+ inches.  Prefers open sun along forest edges. Flowers May – early June with bright reddish-orange fruit in fall.  Can be distinguished from native American bittersweet which has flowers and fruit at the end of its branches.  Competes for sunlight, growing up to 60 ft. It chokes out native plants and trees by smothering them with its dense foliage and strangling stems and trunks.



Spongy Moth

Insect from Europe. Caterpillars emerge from eggs in early spring when they begin feeding on a large variety of trees. Eggs are laid in mid-summer and overwinter. Buff color egg masses contain 75-700 eggs & can be found on tree trunks.  Outbreaks are cyclical.  In 2021, our region had a significant outbreak with major tree damage. Most healthy trees can withstand a year of leaf loss dependent on how much defoliation took place. But defoliation reduces the resistance of trees making them more susceptible to pests and diseases and reach destructive levels.




Invasives that are present in the Adirondacks and are getting closer to Schroon Lake.

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Beech Leaf Disease

Effects and kills both native and ornamental Beech Tree species, which are a significant % of our watershed. It is associated with a nematode (worm) and can destroy mature Beech Trees in 6-10 years and have even killed in one year. Symptoms seen in the leaves including striping, curling and/or leathery texture. These symptoms may be visible from leaf out in May until the leave fall in the Fall. In early infestations, only a few leaves may be affected. A single tree can contain both heavily infected and unaffected branches. The backlighting seen when looking up into the forest canopy can help you spot the leaf striping associated with BLD.


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Spotted Lantern Fly

A highly destructive pest which feeds on wide variety of plants and crops such as grapes, hops, apple trees, maple, walnut, and more than 70 plant species critical to NY’s agricultural economy. SLF feedings stress plants making them vulnerable to diseases and attacks from other insects. They also excrete large amounts of sticky “honeydew” which attracts sooty molds, interfering with plant photosynthesis and negatively affecting the growth and fruit yields. SLF travels easily and can hitchhike on any stationary object. It can reproduce prolifically. Nymphs are black with white spots and turn red before transitioning to adults (active July to Dec.) A preferred host is Tree of Heaven and grape vines




An aggressive underwater perennial, Hydrilla is often referred to as water thyme. It has long stems branching at the surface with small bright green toothed leaves in whorls. Spread by seeds, roots, fragmentation and overwintering buds, it can grow one foot per day. It is one of the world’s worst aquatic invasive plants since it can tolerate various environmental conditions while spreading rapidly, clogging waterways, blocking sunlight to native vegetation and changing a lake’s physical and chemical features. Much like Eurasian Watermilfoil, Hydrilla plants are broken and spread by boats.


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Round Tubenose Goby

It poses a serious threat to eco-systems. A small round fish with protruding eyes, the Round Goby prefers shallow waters and preys on fish eggs, while outcompeting natives for food and nesting sites. During spawning season, Round Gobies are prolific breeders, reproducing every 20 days. Although they eat invasive Zebra and Quagga Mussels, studies have shown that can result in the adverse effect of introducing botulism into the food chain. They also steal bait off of angler’s hooks. Once gobies are established in a body of water, little can be done to eliminate them. Care and prevention by both anglers and boaters is the best method of control.


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Zebra Mussels

Zebra mussels are invasive voracious filter- feeding freshwater bivalve mollusks. They displace native species and attach to many surfaces, have sharp shells and are a nuisance to humans in addition to altering property values. As filter feeders they remove particles from the water affecting the food chain and ecosystem, effectively starving out many native zooplankton species. They attach to all hard surfaces including boats, water intake pipes, rocks, docks, etc. Zebra Mussels have D shaped shells which are typically fingernail size to less than 2 in. long with a striped pattern. Color can vary from light to dark. They attach to all objects including other mussels with Byssal threads. Zebra mussels can inhabit depths to 50 ft. Once established, very little can be done other than manual removal They are introduced into new bodies of water through boat bilges, live wells, bait buckets etc. The best way to prevent the spread is to Drain, Clean and Dry all equipment that will come in contact with our waterways.




Black and pale swallow-worts are herbaceous, perennial, twining vines which spread quickly and form dense mats that choke out large areas of favorable species and interfere with forest regeneration. They can be found in many habitats including woodlands, fields and roadsides. Both species look similar when not in flower and have 3-4“long by 2-3“wide oval dark green leaves are opposite and glossy. Pale swallow-wort leaves tend to be a lighter shade of green. Flowers of both species are similar and star-like. Small five petaled star-like maroon to pale pink flowers are present in late May through July. In late summer, abundant seed ponds (1 ½ - 3 “long) are smooth, slender and pointed, and split open releasing innumerable downy seeds.


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Water Chestnut

Black and pale swallow-worts are herbaceous, perennial, twining vines which spread quickly and form dense mats that choke out large areas of favorable species and interfere with forest regeneration. They can be found in many habitats including woodlands, fields and roadsides. Both species look similar when not in flower and have 3-4“long by 2-3“wide oval dark green leaves are opposite and glossy. Pale swallow-wort leaves tend to be a lighter shade of green. Flowers of both species are similar and star-like. Small five petaled star-like maroon to pale pink flowers are present in late May through July. In late summer, abundant seed ponds (1 ½ - 3 “long) are smooth, slender and pointed, and split open releasing innumerable downy seeds.




These invasives are not yet in the Adirondacks, but in New York State and/or Vermont. ESSLA is closely monitoring their status.  For details on our watch list invasives, visit APIPP's website at


If you see something you suspect may be an invasive, note the location, take pictures and report it to

Thanks for your help!

  • Autumn Olive

  • Asian Longhorn Beetle

  • Bloody Red Shrimp

  • Brazilian Eloda

  • Buckthorn

  • European Frog-bit

  • Fanwort

  • Hogweed

  • Kudzu

  • Mile a Minute Weed

  • Oak Wilt

  • Porcelain Berry

  • Southern Pine Beetle

  • Spiny Water Flea

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