Eurasian Watermilfoil in Lake George

Photo courtesy of: Alison Fox, University of Florida, Bugwood.org

Eurasian watermilfoil (Myriophyllum spicatum) was first discovered in Lake George in 1985. As part of a coalition of organizations, the Lake George Association is working to remove milfoil from Lake George, investing tens of thousands of dollars each year to hand-harvest the plants and cut back in the invasive species' footprint. Additionally, we swim through and survey milfoil sites in Lake George multiple times each summer to ensure the removal process is effective after our contractor has stopped working in an area.

But it is not an easy job. Because the plant self-fragments, pieces of milfoil from patches break off and re-root nearby, confounding efforts to completely eradicate it. By 2016, the aquatic plant had spread to 216 known sites, though at least 30 of those sites were removed from active "inventory" because hand-harvesting or other treatment had left the site with no active growth of the invasive species. Several methods to control milfoil in Lake George have been used, including hand harvesting and matting.

See the 2016 Comprehensive report of milfoil management operations on Lake George - pdf.

What is Eurasian watermilfoil?
This invasive aquatic plant is native to Europe, Asia and North Africa. It was first documented in North America in 1942 in the District of Columbia. It was most likely brought to this continent in the ballast of a ship and has since spread to almost every continental state and throughout Canada.

Photo courtesy of: Leslie J. Mehrhoff,
University of Connecticut, Bugwood.org

Why is it a problem?
Eurasian watermilfoil spreads easily and grows quickly. Eurasian watermilfoil crowds out native plants, reducing biodiversity, diminishes fish habitat and negatively impacts wetland habitats. Dense mats form near the surface.  They entangle boat propellers and interfere with swimming and fishing.  As a result, Eurasian watermilfoil can adversely affects our local tourist-dependent economy.

What does Eurasian watermilfoil look like?
Eurasian watermilfoil resembles the native Northern Watermilfoil (Myriophyllum sibiricum), however there are several distinguishing characteristics that can be used to differentiate between the two species.  Unlike the Eurasian variety, Northern milfoil offers shade, shelter and foraging opportunities for fish. Click here to print out the LGA "Good vs. Bad" Milfoil card - pdf. Click here for a Milfoil Look-a-Likes fact sheet - pdf that includes additional look-a-like species.

Eurasian Watermilfoil

Native Northern Watermilfoil

  • 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 are limp when out of water
  • Stem is as thick or thicker than a pencil and is long and spaghetti-like
  • Usually 7-10 leaflet pairs per stem
  • Rigid feather-like leaves form a Christmas tree shape
  • Lower leaflets are usually quite long
  • Leaves arranged in whorls (circles) of four to six around stem
  • Leaves are usually rigid when out of water
  • Stem is usually whitish, or whitish-green in color

What should you do if you find Eurasian Watermilfoil in Lake George?
Leave it alone.  As a homeowner you can carefully remove plants immediately around the area of your dock. (Read more details in the Adirondack Park Agency's Advice for Hand Harvesting - pdf)  You need to know what you are doing because if you break the plant up you will just create more plants and do more harm than good.  Eurasian Watermilfoil reproduces through vegetative propagation, so each tiny bit that floats off can form a new plant. 

If you find an area of Eurasian watermilfoil, email the LGA or call us at 518-668-3558.  Alternatively, you can check the location maps - pdf to see if the Lake George Park Commission knows about the bed.

Where is it located in Lake George?
As noted above, the 2016 Report explains that a total of 216 Eurasian watermilfoil sites have been identified. In the southern basin, there are high concentrations of milfoil sites near human population centers and boat-use areas including, but not limited to Lake George Village, Bolton Landing, Harris Bay, Warner Bay, Dunham's Bay, Huddle Bay and off of Long Island. In the north basin, clusters of Eurasian watermilfoil sites are also found in areas of high use near Huletts Landing, Putnam, Hague, and Roger’s Rock

A total 80,500 pounds -- or about 40 tons -- of Eurasian watermilfoil was harvested in 2016.

Management activities in Lake George continue to have a positive impact on the control of many milfoil sites.

Photo credit: NYS Dept of Environmental Conservation

How does Eurasian watermilfoil spread?
The primary way Eurasian watermilfoil spreads is through vegetative reproduction. This spread is mainly through fragmentation of plant tips or through root expansion.  With fragmentation, even a very small piece of this aquatic plant can float away, re-root and begin a new colony. It is easily fragmented and moved around within lakes by boats, or between lakes on boats and trailers. Eurasian watermilfoil milfoil can form thick, floating mats of vegetation, clogging the water and hindering recreation. It can grow in water 0.5 -10 meters deep.

 

 

 

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