Watershed Management Bureau

  Exotic Species Program

  Weed Control Diver Course - May 10, 2008

  2008 Proposed Herbicide Applications for Variable Milfoil Control in New Hampshire

The DES Exotic Species Program coordinates activities associated with the control and management of exotic aquatic plants; as well as activities associated with the implementation of education programs and volunteer plant monitoring programs.

Exotic aquatic plants, such as milfoil and fanwort, have been a problem in New Hampshire lakes and ponds since the mid-1960s. Variable milfoil, by far the most wide-spread exotic aquatic plant in NH, was first found in Moultonborogh Bay in Lake Winnipesaukee. From there it has spread to infest 38 waterbodies.  Fanwort, water chestnut, Eurasian milfoil, purple loosestrife, and common reed are also problematic species in this state.

Why are these plants such a problem? Native plant communities have evolved together over hundreds of years. Animal and insect grazers have become specialized to feed on these native plants. Since exotic plants are introduced from outside of the state, they have no established relationships with native fauna that would keep their growth in check. When these exotic plants grow without natural controls they encroach into and replace the habitats of native plants, disrupting the food chain, stunting fish growth and degrading wildlife habitat.

Other states besides NH are also faced with the problem of exotic plants, and unfortunately, no one has yet found a practical, ecologically sound means of eradication for these plants. Once in a waterbody, continuous management and control practices are the only tools to control the nuisance plant growth.

It therefore becomes increasingly more important to prevent infestations, and to identify new infestations early. DES biologists conduct numerous field investigations each summer, but with over 800 lakes and ponds in the state, the efforts of volunteers in monitoring waterbodies for new infestations become critical. Through materials and training sessions by DES, numerous lakes and ponds have initiated their own Volunteer Weed Watching programs.

For more information, please contact the Exotic Species Coordinator at 603-271-2963 or

Amy P. Smagula
Limnologist/Exotic Species Program Coordinator
NH Department of Environmental Services
29 Hazen Drive, PO Box 95
Concord, NH 03302-0095
Phone: 603-271-2248
Fax: 603-271-7894
E-mail: amy.smagula@des.nh.gov

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