Milfoil Treatment

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 (trade
name 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:
  • No swimming for 7 days
  • No drinking of lake water for up to 30days (depending on water test results)
  • 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.

Click here for a list of waterbodies being treated by these companies in NH:

2009 Proposed Herbicide Applications in NH
The information posted on this
website is believed to be
accurate and is based on
research, interviews, and
meetings attended by the
associations officers, directors,
and/or members.
Join the Namaske
Lake Association to
help assure that
Namaske Lake is
clear of Milfoil.
Herbicide is
applied in lakes
with the use of
specially
modified  boats.