Treatment Process & Info

Milfoil Treatment

It is against the law in New Hampshire to remove or treat milfoil without a permit or dive certification. However, according to DES:

IF IT’S JUST ONE NEW STEM THAT COMES UP YOU CAN HAND REMOVE IT TO KEEP IT FROM SPREADING.  YOU NEED TO FOLLOW THE STEM DOWN INTO THE SEDIMENT AND GRAB THE ROOTS AND THE GREEN SHOOT OF THE PLANT AND REMOVE ALL FROM THE LAKE/SEDIMENT.  YOU CAN DISPOSE OF IT IN THE TRASH OR IN THE WOODS/GARDEN AS LONG AS IT’S WELL AWAY FROM THE LAKE AND CAN’T GET BACK IN.

NH-DES, creates infestation maps, and provides the Association with detailed data to obtain treatment quotes form qualified vendors.  These treatments include the use of chemicals, such as herbicides, for the control of noxious and nuisance plant species represents one of the most widely known and effective management options available.

Herbicide control of invasive aquatic plants is often the first step in a long-term integrated control program. In the last 15 to 20 years the use and review of herbicides has changed significantly in order to accommodate safety, health, and environmental concerns. Currently no herbicide product can be labeled for aquatic use if it has more than a one in a million chance of causing significant harmful effects to human health, wildlife, or the environment. Because of this, the number of effective and U.S. Environmental Protection Agency (EPA) approved herbicides for aquatic weeds are limited. In most cases the cost and time of testing and registration, rather than environmental issues, limits the number of potentially effective compounds.

All herbicide applications in New Hampshire are performed under permits issued by the New Hampshire Department of Agriculture, Division of Markets and Food, Bureau of Pesticide Control.

Two herbicides have been used in New Hampshire for the control of milfoil. Diquat (tradename Reward), the most often-used herbicide, is a contact herbicide that can generally provide one season of control for milfoil. Because this herbicide does not target the root systems, the plants eventually re-grow from established roots. The second herbicide, 2, 4-D (trade name Navigate or Aqua Kleen), is a systemic herbicide. It is absorbed into the sediments and taken up through the root system, killing both the roots and the plant biomass above the sediments. Label restrictions for aquatic application currently limit its use in New Hampshire to waterbodies with no water intakes, and with no wells adjacent to the shoreline.

The aquatic herbicide SONAR has been used in New Hampshire to control growths of fanwort. The chemical acts by limiting photosynthesis when chlorophyll-a is affected by the active ingredient of the herbicide.

According to Lycott Environmental Inc. (one of the approved State contractors), they typical treatment cycle/schedule would be as follows:

  • Notification of abutters along the area to be treated that a license has been granted for treatment.
  • Notification to abutters of when treatment will take place.
  • The pellet herbicide is applied from an airboat, and will take around 1/2 a day to cover our lake.
  • Restrictions:
  1. No swimming for 7 days
  2. No drinking of lake water for up to 30 days (depending on water test results)
  3. No irrigation with lake water for up to 30 days (depending on water test results)
  • Milfoil will die within a few days, and collapse on the lake bottom.
  • The milfoil will rot at the lakes bottom – no further removal is required.
  • Lake will have to be monitored, and will likely require a second treatment within 2 – 5 years.

NH DES Approved Herbicide Application Contractors:

  • Lycott Environmental Inc.
  • Aquatic Control Technology, Inc.