Eurasian
Watermilfoil
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news around the Lake, please check out our Waterlines Newsletter issues - links
may be found on our home page. Thank you.
Huron Pines 2007 Milfoil Survey
Click
here to view 2007 survey.
Click
here - Map 1 recommended milfoil treatment 2008
Link
to Huron Pines Milfoil Report on their website
Milfoil growing along the
drop-off at Flag Point
Prolific
areas of milfoil near drop-off between Detroit Point and
Old
Point Comfort - photo on left shows a barrier next to a wall of milfoil.
Photo
on right shows thick patch of milfoil growing almost to the surface
of
the lake, and choking out native vegetation.
Huron
Pines RC&D
Project
Fact Sheet July 2004
Higgins
Lake
: A five
star approach to controlling Eurasian watermilfoil
The July 12 stocking of two weed beds in
Higgins
Lake
with the “milfoil
weevils” is the latest attack on controlling the spread and growth of Eurasian
watermilfoil in order to protect both the lake ecosystem and the recreational
opportunities it provides. Eurasian
watermilfoil (EWM) is an invasive exotic species thought to have first entered
lakes in
North America
in the 1940s.
EWM is a concern because it rapidly colonizes lakes and spreads easily by
fragmentation. The plant can grow to
the surface of the water and form extremely dense mats, inhibiting boating,
fishing and swimming. It also crowds
out some of the more ecologically beneficial aquatic plants. Once established,
Eurasian watermilfoil is very difficult to remove and can be spread from lake to
lake by boat traffic.
Higgins
Lake
is a 9,900-acre
high-quality lake located in
Roscommon
County
.
The lake, 140 feet at its deepest point, is a tremendous natural
resource, attracting thousands of people to live near it and thousands more to
visit each year
Above,
biologists with Enviroscience prepare to stock
milfoil weevils at an EWM site in
Higgins
Lake
.
During
the period of June 2001 through December 2002 local citizens, organizations, and
resource agencies were involved with developing a watershed management plan for
Higgins
Lake
.
As an outgrowth of that project, the Higgins Lake Foundation funded an
assessment of Eurasian watermilfoil (EWM). The
survey was conducted late June/early July of 2002 by Huron Pines Resource
Conservation & Development Council and repeated in 2003. It was conducted in
order to identify major EWM weed beds in the lake, characterize
the extent of the problem, and provide baseline information for analysis of
future management options.
With its sandy substrate and low nutrient
levels, Higgins does not appear as susceptible to colonization of EWM as many
other lakes in
Michigan
. Due to
the fact that EWM can take hold quickly, addressing these small areas of plant
growth is essential to
the successful control of EWM in
Higgins
Lake
.
In addition, EWM is well established in several sections of the lake.
The EWM inventories highlighted 12 priority areas of concern; these areas
are the focus of treatment efforts by project partners.
These sites include the drop-off areas along Point Detroit and Flag
Point, the three major (state-owned) boat launches, a large weed bed several
hundred feet from shore between a private marina and Camp Westminister, two
sites several hundred feet off Cheney Point, an area where numerous small
growths are being established near Treasure Island, a two sites south of Flag
Point, and one weed bed between the shore and drop-off in the southwest section
of the lake. (For more detailed site information, contact
Huron Pines RC&D
at
989/348-9319.)
The
key to effective control of Eurasian watermilfoil in
Higgins
Lake
is to think in terms
of the long-term management of the lake. The
course of action should be realistic, cost-effective, and ecologically sound.
Due to the unique characteristics of
Higgins
Lake
and the fact that the
EWM problem is in its early stages,
Huron Pines RC&D
staff recommend an integrated
management program tailored specifically to
Higgins
Lake
.
The involvement and support of community organizations and residents
around the lake has made such an approach possible.
The strategy, employed one small site at a time, is designed for the
long-term health of the
Higgins
Lake
ecosystem, keeping
costs – both financial and ecological – to a minimum.
The integrated management program, a five-star approach to control of EWM,
includes the following: 1) Biological control, 2) Chemical treatment, 3)
Physical control, 4) Community Outreach, and 5) Continued monitoring.
Biological
control methods,
specifically predation of the plant by an aquatic weevil (Euhrychiopsis
lecontei), have been successful in many
Michigan
lakes. This method of
control can be expensive initially and time is needed to tell how well a weevil
population will sustain itself and provide long-term control; however, this may
well prove to be the most effective treatment over time. In
the summer of 2002, while collecting some plant samples, biologists with the US
Army Corps of Engineers were able to find these herbivores naturally occurring
in
Higgins
Lake
.
To supplement the natural population,
Huron Pines RC&D
contracted with the
Ohio-based company Enviroscience to stock 10,000 milfoil weevils at two of the
more problematic locations in
Higgins
Lake
(Flag Point and the
weed bed near between
Camp
Westminister
and B&B Marina).
Follow-up study of these two sites during the next three years will help
determine whether this method should be used on a greater scale in
Higgins
Lake
.
Funding for the weevil project was administered by the Muskegon River
Watershed Assembly (MRWA) with project coordination help from the Higgins Lake
Property Owner’s Association. A
dollar for dollar matching grant, through MRWA’s partnership with the Wege
Foundation, allowed local contributions from the
Higgins
Lake
area to get twice as
much done for the resource as they otherwise would have been able to.
Local contributions came from the Higgins Lake Foundation and the
Schroeder Foundation. Also
contributing to the effort were The Robert R. Thalner Endowment Fund and the
John Morley Family – Higgins Lake Endowment Fund of the Roscommon County
Community Foundation.
The use of
herbicides
to treat a lake is a very expensive approach that raises several concerns.
These include the immediate effect of the application on non-targeted
species, the fact that long-term impacts on all organisms are poorly understood,
treatments will likely need to be repeated in future years, and the high
potential for re-infestation. “Whole
lake” chemical treatment is not appropriate for
Higgins
Lake
because Eurasian
watermilfoil is not found in abundant amounts throughout the lake and because of
the large volume of water. Limited
use of an herbicide for spot treatment at the three DNR Boat Launch sites will
be used in 2004 as these public access points seem to be the main entry point
for EWM into
Higgins
Lake
.
Without eliminating EWM from these three locations, the invasive plant
will continue to be introduced into
Higgins
Lake
and efforts to control
its growth would ultimately fail.
Above,
scuba divers place a benthic barrier in
Higgins
Lake
.
Physical
control,
such as the placement of a bottom (or benthic) barrier on the lake bottom, has
also been used to control EWM. This
is an ecologically sound, low-cost method for small problem areas, although it
is labor intensive to install and can be difficult to maintain.
By blocking out sunlight, EWM is prevented from growing.
This treatment was used in 2003, as a pilot project, at 4 locations in
the lake. At three of the four sites
in 2003, the treatment worked effectively. At
the fourth site, the material was dislodged by boat anchors.
(The unsuccessful site was thus targeted for treatment with the milfoil
weevils in 2004.) Because of the success of this approach, the treatment was
once again used in 2004 at four sites. Through
the volunteer efforts of teams of scuba divers, the sites are checked each week
and any maintenance work performed as necessary. The material, a geo-textile
fabric held in place by stakes and a small amount of rock, was cut into 15’ by
30’ panels for ease of installation by a 3-person team of scuba divers.
While the fabric is somewhat permeable, holes are cut into it to allow
the escape of gas from bottom sediments.
Above,
geo-textile fabric is used in a 2,500 square foot EWM weed bed in
Higgins
Lake
.
Note
the growth of plants where the barrier is not shading out the plants.
The
other form of physical control of EWM, plant harvesting, refers to both pulling
the plant by hand as well as using a machine.
Because fragmentation of EWM leads to its spread, mechanical harvesting
is not
a viable option for
Higgins
Lake
.
Careful hand harvesting may work in areas where only a small cluster of
EWM is present. Once again, EWM
spreads through fragmentation, so hand harvesting must be done with the utmost
care. All plant fragments should be
collected and disposed of off-site. The
benefit to this approach, on a micro scale, is that EWM can be prevented from
fully establishing itself.
Community
Outreach and Education
is as important to solving the milfoil problem as any other method of control.
Whether it is the use of effective signage at boat launches, the 2003
direct mail distribution of EWM identification cards to property owners, or the
2004 “Look Before You Launch” card pictured below (for distribution at
launch sites), all stakeholders that enjoy Higgins Lake need to know that they
ultimately play the key role in helping to protect it.
Key messages, such as, “Boaters need to wash watercraft and dispose of weeds before entering and
exiting
Higgins
Lake
,”
are very important for everyone to understand and act on.
Continued
Monitoring is the final component of the five-star program for managing milfoil.
It is vital so that project partners can implement control efforts as
soon as EWM if found, before it gets out of hand.
The early intervention approach, along with persistence, can ensure the
health of
Higgins
Lake
.
For more information on identifying or reporting EWM, contact
Huron Pines RC&D
at 989/348-9319.
Because EWM has been documented early on in its infestation of the lake, there
is a great opportunity to use a hybrid method of biological control, outreach
and education, limited use of chemicals, and physical control techniques to
reduce the spread of this invasive plant and help protect
Higgins
Lake
for years to come.
Above,
a milfoil weevil treatment site along the drop-off at Flag Point.
Eurasian Water Milfoil Project (2003)
Eurasian
Water Milfoil Project Report
