Eurasian Watermilfoil is an invasive plant that threatens Chateaugay Lake

Invasive species threaten waterbodies and landscapes and are a growing concern locally, nationally and globally. Once established they are difficult and expensive to control. Invasive species cost $137-$146 billion annually in the United States. In the case of Chateaugay Lake, over $668,000 has been spent since milfoil control began in 2008, averaging about $43,000 annually.

Species that are non-native to our lake and region and likely to cause ecological or environmental harm are considered “invasive.” A non-native species becomes invasive when it lacks predators and native parasites; produces many offspring/seeds; reproduces by multiple means; is a generalist outdoing natives for space; and monopolizes resources. In the absence of ecological controls such as disease and predators, non-native species can out-compete natives, which depletes the lake’s native biodiversity.

In Chateaugay Lake, the invasive aquatic plant Eurasian Watermilfoil is a serious problem and other invasive threats are on the horizon. The CLF works to prevent the establishment and spread of invasive species in Chateaugay Lake and its watershed.

What is Eurasian Watermilfoil?

Milfoil (Myriophyllum spicatum) is an invasive aquatic plant native to Europe, Asia and North Africa. It may have been first documented in North America in the 1940s and likely arrived either as ballast in large container ships or through the aquarium trade. Since it is not native to our waters, there are no natural predators to prevent its spread. This highly invasive aquatic plant has become notorious in the Adirondacks and beyond for clogging waterways, crowding out native plants, degrading wildlife habitat, and spoiling boating, fishing and swimming. Chateaugay Lake has native milfoil species that are non-invasive and other native plants that look similar to Eurasian watermilfoil and learning the difference is important.

What does Eurasian watermilfoil look like?

  • Usually 12-21 leaflet pairs per leaf
  • Delicate, feather-like leaves
  • Leaflets are mostly the same length
  • Leaves arranged in whorls (circles) of three to five around each stem
  • Leaves become limp when out of water
  • Leaflet ends with a blunt tip
  • Tiny reddish flowers may be found at the end of the stem blooming in late July to August
  • The stem is long and spaghetti-like. It can reach a length of 25 feet
  • It can be red to a light brown color
  • Each stem can branch several times as it reaches the water surface, forming a dense floating mat
  • The mats break up in late July and litter the shoreline

Eurasian Watermilfoil’s native look-alikes



 Bladderwort is a carnivorous aquatic plant. It can be distinguished from milfoils by the small “bladders” along its leaves that capture small aquatic organisms. The flowers are yellow and grow above the water’s surface. This plant is native to Chateaugay Lake.



Coontail is a rootless native plant that floats freely. It can form dense formations in the water. Leaves grow in whorls of nine or ten on a stiff stem. The plant is very bushy and when taken out of the water resembles a raccoon tail. The stems and leaves maintain their shape when removed from the water. Coontail is native to Chateaugay Lake.

Northern Watermilfoil

Northern Watermilfoil

Eurasian watermilfoil looks similar to native watermilfoils that are found in our lake. One common native look-alike is northern watermilfoil.

Northern watermilfoil has only five to nine leaflet pairs, the space between whorls is short, and when removed from the water the leaves hold their shape, unlike Eurasian watermilfoil which collapses when removed from the water.

Eurasian and northern watermilfoils often hybridize. Hybrids have similar characteristics and may require genetic screening to distinguish them from non-hybrids.

How does it spread

How does it spread?

Milfoil spreads mainly through fragmentation of plant tips or through root expansion from rhizomes that anchor the plant to the lake bed. With fragmentation, even a very small piece can float away, re-root and begin a new plant. It is easily fragmented and moved around within lakes by boats or just by wind and wave action, or between lakes via boats and trailers.

Why is it a problem?

Milfoil spreads easily and grows quickly. Milfoil crowds out native plants, diminishes fish habitat and negatively impacts wetland habitats. Dense mats form near the surface. They entangle boat propellers and interfere with swimming and fishing. Multiple drowning deaths in the United States have been attributed to entanglement in milfoil. Eventually, milfoil impacts property values by decreasing the attractiveness, safety and enjoyment of the shoreline of the lake.

Photo: a boat on Hayden Lake in Idaho ISDA (

Boat prop with milfoil

Prevent Spread

Photo: Upper Chateaugay Lake buoys in the south inlet mark a large milfoil bed.

Milfoil Protocols

  • Learn to identify milfoil and how to prevent accidentally spreading it with your boat or fishing equipment.
  • Avoid infested areas. The CLF has buoys that mark a large dense bed in the south inlet of Upper Chateaugay lake. In 2021 we will be installing marker buoys in the inlet to Lower Chateaugay lake to mark a milfoil free boating lane.
  • If boating through a milfoil area, reduce your speed and remove any plants that become entangled in propellers and dispose of on shore.
  • If washed up on your shore, or caught in your boat’s prop, or snagged on your fishing line, please do not throw it back into the water. Dispose of milfoil on shore at least 100 feet from a water source so it does not wash back into the lake.
Chateaugay Lake Boat Wash Station
Chateaugay Lake Boat Wash Station, DEC Boat launch.

Clean, Drain And Dry

  • Inspect your boat, trailer and equipment after each use. Dispose of plant matter well away from water sources.
  • Clean boats and trailers with 140 degree water using a pressure washer or a stiff brush. Free wash stations can be found throughout the Adirondack Park including the DEC boat launch located on Rt 374 on the Chateaugay Narrows.
  • Empty bilge and bait wells.
  • Let boats dry out for 5-7 days between water body visits, leaving boats in the sun.
  • Disinfect anything that cannot be dried before reuse. A 2% solution of bleach is recommended.

Other Species of Concern

Unfortunately, milfoil is not the only invasive species that threatens our lake. The CLF is involved in monitoring the lake for other invasive species that are spreading throughout the Adirondack Park. Curlyleaf pondweed, an invasive aquatic plant, is found in the Narrows as isolated plants or in small clusters. Chinese Mystery snail has been present in Chateaugay for many years. In addition, zebra mussels, hydrilla, and spiny water-flea, among others, remain a threat but fortunately have not been identified in Chateaugay. Finally, a terrestrial invasive insect called woolly adelgid that kills off hemlock trees has been identified as far north as Lake George and could have a devastating impact on our watershed. CLF partners with other organizations in the park including the Adirondack Watershed Institute (AWI), and the Adirondack Park Invasive Plant Program (APIPP), among others, to keep abreast of these threats. The message here is keep educated about threats and remain vigilant!

Curly-Leaf Pondweed

Curlyleaf Pondweed

This invasive plant is most recognized by its lasagna like crinkled leaves. It grows very early in the season and is usually gone by mid-July. The leaves are two to three inches long and have tiny serrations. The stem is reddish brown. It reproduces by a winter bud called a turion. It can be difficult to distinguish from clasping leaf pondweed.

Status in Chateaugay: Found in the Narrows and targeted for hand harvesting. Previously found and removed from spots in the Upper and Lower Lakes.

Spiny Waterflea

Spiny Waterflea

Spiny water flea is a zooplankton. It is very small and may not be detectable to the eye unless clumped together on something like a fishing line. Its exoskeleton is so unpalatable that no predators want to eat it. It is a dangerous invasive because it causes a breakdown in the food web from the bottom up and will seriously impact fishing in the lake.

Status in Chateaugay: Absent

Zebra Mussels

Zebra Mussels

Zebra mussels have been found in nearby Lake Champlain. They are prolific eaters filtering out impurities in the water. Cleaner water allows for light to penetrate deeper in the water column. It results in greater plant growth, including invasives. It also allows for deeper light penetration making waters warmer and impacting the cold water loving fish present in our lake.

Status in Chateaugay: Absent



Hydrilla is called the world’s worst aquatic invasive species because it grows so quickly once established in a waterbody. Its stems can be up to 25 feet long and it forms thick mats. Hydrilla could cause serious disruption to the ability to use our lake.

Hydrilla looks very similar to a native Elodea in Chateaugay. However, hydrilla has:

  • Pointed, bright green leaves about 5/8 inches long.
  • The leaves grow in whorls of 3 – 10 along the stem, 5 being most common
  • The edges of the leaves are serrated but these teeth are very tiny and may need magnification to see
  • It has thin stems that have a single, small, floating white flower

Status in Chateaugay: Abset

Chinese Mystery Snail

Chinese Mystery Snail

This snail was likely brought to the US from East Asia possibly as a source of food. They are large and have a distinctive bad smell. They impact the food web taking resources from smaller native snail species. They can also clog water intakes. Their shells break easily into sharp shards that cause cuts on bare feet.

Status in Chateaugay: Endemic throughout the lake

Hemlock Woolly Adelgid

Hemlock Woolly Adelgid

The Wooly Adelgid is an aphid-like insect that feeds on the sap of hemlocks causing death to the trees. In the fall, the insect attaches to the stems of new growth and creates a wooly covering so they can overwinter. The hemlock forests of the Adirondacks would be significantly impacted as well as our watershed if this invasive pest finds a foothold. The Adelgid has recently been found in Lake George and is migrating north.

Status in forests around Chateaugay: Absent

Special Guidance for Anglers

Use only certified bait

The DEC has a list of all acceptable bait that can be used in freshwater bodies within NY. This list can be found at

However, several bait fish on the NYS list should not be used in the Adirondacks including Blunt Nose Minnows, Golden Shiners, Jumping worms (aka crazy worms), and the Rusty Crayfish.

Be sure to buy bait only from certified dealers. NY requires that you keep a copy of your baitfish purchase receipt and be prepared to show the receipt if asked by authorities.

Use proper bait disposal

  • never release live bait from a bait bucket into any waterway
  • dispose of fish carcasses into the trash
  • drain bait buckets and fish wells onto land
  • rinse all waders before moving waterbodies
  • don’t use felt bottom waders because they can spread invasive species
  • collect all lines and lures-do not leave them hanging from trees or stuck in rocks
  • encourage others to follow these rules