Milfoil in Lake Fairlee – July 2010 Update

[ We were asked to provide a brief statement on the milfoil in Lake Fairlee to be used by the guides on the boat tours of the lake offered as part of LAKEFEST 2010. We include it here, as it provides a concise summary. ]

Eurasian Milfoil is a floating aquatic plant native to Europe, Asia, and northern Africa. It was imported and sold in the United States as a decorative aquarium plant. It has become a problem in many northern lakes, and has been in our lake for over fifteen years. It grows faster than many native lake plants, and tends to crowd out the native plants and can drastically alter a lake’s ecology.

Because it roots in the lake bottom and reaches for the sunlight at the surface, it grows primarily in water less than 15 feet deep. Even a small fragment can take root, so it spreads easily within a water body and from lake to lake, traveling on boat bottoms and trailers. In the spring it is frail and brittle, and easily fragmented. In the summer it grows strong and thick. If allowed to spread unchecked it threatens to clog the lake with dense mats of plant material. Parts of the lake can become inhospitable to boaters and swimmers, and ultimately property values and tax revenues may suffer.

The Lake Fairlee Association recognized the threat posed by Eurasian Milfoil fifteen years ago, and began a series of escalating responses intended to eliminate or at least control it.  Initially we used hand pulling of the plants and their roots.  In 2002 we began using bottom barriers for some of the most problematic areas.  In 2004 we built and deployed a suction harvester to make the hand pulling much more efficient.

These methods were not sufficient.  In fact, the milfoil has continued to spread in spite of our best efforts.  Scientific surveys we had conducted last summer found moderate or dense milfoil growth in 26% of the lake.  Late this spring we obtained a permit from the State to treat the lake with an herbicide, triclopyr, to which the milfoil is particularly susceptible.  In early June Lycott Environmental, Inc., a firm licensed to do this kind of work in Vermont, applied triclopyr to the areas of heavy milfoil growth.

The chemical has had its effect, and the milfoil in the lake is now dead or dying.  Most of the plants can be seen decaying on the bottom of the lake.  There has been negligible effect on other species of plants, and no observed effects on fish, birds, or other animals in the lake.  We have been testing the lake water in ten locations since the treatment, and the State has declared the lake’s water safe for drinking – at least as far as the herbicide concentration is concerned!

Late this summer another detailed survey will ascertain just how successful our treatment has been.  Until then we will enjoy swimming and boating in the open water of the lake.  And we will redouble our efforts at educating boaters how to wash their boats and equipment to curtail the further spread of milfoil and other aquatic nuisances from lake to lake.

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