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. By 2011, the aquatic plant had spread to 191 known sites. (See maps of where it is located - pdf.) Several methods to control milfoil in Lake George have been used, including hand pulling and matting. The Lake George Park Commission (LGPC) manages Eurasian watermilfoil on Lake George. See the 2011 LGPC report - 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 Lake George Park Commission (LGPC) 2011 Report - pdf to see if the LGPC knows about the bed.

Where is it located in Lake George?
The 2011 Lake George Park Commission Report - pdf explains that a total of 191 Eurasian watermilfoil sites have been identified. Approximately half of these sites are located in the southern basin, with high concentrations near human population centers and boat-use areas including: Lake George Village, Bolton Landing, and the southeastern shallow bays (Dunham's, Harris and Warner). In the northern basin, clusters of milfoil colonies are also found in areas of high use near Hulett’s Landing, Putnam, Hague, and the outlet.

173 sites were cleared of Eurasian watermilfoil in 2011. Combining Lycott hand harvesting and benthic barrier data, a total estimated 785,200
plants were removed in 2011.

Management activities in Lake George have had a positive effect on the control of many milfoil sites. However, seven sites remain with dense milfoil beds and eleven sites have moderately-dense growth. As of 2011, a total of 173 sites have been successfully cleared or managed. Thus, in addition to routine annual effort, 18 of the 191 total sites in Lake George require significant future effort.

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.