Environmental Science & Engineering - www.esemag.com - May 2003
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Tiny insect to tackle eutrophication in Quebec lake
Canadian lakes are to be rescued
by a tiny insect the size
of a sesame seed. It has six
legs and is a dedicated vegetarian.
This tiny beetle called the milfoil
weevil has recently proven it is
capable of handling an invasive weed.
Eurasian Watermilfoil (EWM), one of
the most invasive and notorious exotic
plant species in North America, is
engaged in a highly aggressive infestation
on fresh bodies of water. The plant
is responsible for serious impairment
of swimming and boating,
habitat loss and native
species decline in lakes
across the U.S. and
Canada.
The US Army Corps
of Engineers has listed
EWM as a major threat
for domestic lakes. It
thrives in a wide range of
water conditions, spreads very
quickly and is capable of choking out
native plant species that are essential
for fish habitat and overall lake health.
Since its accidental introduction to the
U.S. in the 1930s from the aquarium
trade, the situation had become
increasingly desperate.
In 1998, a group of biologists, led
by Dr. Sallie Sheldon at Middlebury
College in Vermont, theorized that the
naturally occurring milfoil weevil
would have a taste for the exotic variety
of milfoil. Marty Hilovsky, president
of EnviroScience, Inc., in Stow,
Ohio, realized the potential for this
innovative idea, and soon thereafter
acquired the sole rights to market it.
“Essentially what we’ve done is to take
advantage of a highly effective predator-
prey relationship,” he said.
While in the larval stage, the weevils
are voracious eaters and quickly
dispose of the plant’s long stems—ultimately
this stops the plant from nourishing
its branches and spreading. The
weevils have a built-in appetite for a
naturally occurring variety of milfoil –
although the exotic version must
taste much better, because the
weevils go after EWM. The
weevils also reproduce
quickly and can breed
three to five generations
of hungry larvae per summer.
The process was eventually
named MiddFoil®.
Biocontrol strategies for
controlling invasive exotic species
are becoming a more commonplace
solution, despite the fact they often
take a longer period of time to solve
the problem. Previous strategies for
eradicating milfoil have all proven to
have side effects and/or they are simply
ineffective as a long-term solution.
Herbicides only provide 1-2 years of
relief at most and are potentially harmful
to native plants and animal species.
Mechanical harvesters can bring shortterm
relief, but ultimately help the milfoil
spread—broken milfoil fragments
easily flourish and form new colonies.
The introduction of exotic grass carp,
an early attempt at biocontrol, did not
work. Grass carp are not EWM specific.
In fact, they often wipe out native
aquatic plants before targeting EWM,
and this is very harmful to the habitat
needs for native fish, insects and various
invertebrates.
“We now have more than five years
of documented results for the
MiddFoil process,” stated Hilovsky.
“The data are very favorable – milfoil
weevils are the only proven long-term
solution that is currently available,” he
added. Perhaps the most unique aspect
of MiddFoil‚ is that it uses a native
insect to control an exotic species.
Although each lake responds somewhat
differently, Hilovsky stated that
the Lac Cayamant, Québec project,
scheduled this summer, “will be the
first MiddFoil project in Canada,
although there are numerous successful
projects in the Midwest and Eastern
U.S. We believe that this insect is very
well adapted to more northern climates,
so the relatively long, cold winters
shouldn’t be any problem for our
weevils,” he said. “Lac Cayamant also
has exactly the right shoreline characteristics
that should make for a good
MiddFoil project.”
Because each lake is different, each
strategy is different. Each body of
water will have different levels of
infestation, so a customized solution is
created for each project.
The strategy usually involves the
calculated deployment of tens of thousands
of weevils into targeted areas in
each lake. This process repeats itself
for several years, with each application
typically becoming smaller as the
EWM beds are eliminated. And further
proving the beauty of this biocontrol
strategy, the weevil population naturally
adjusts to its food source so
there is no concern about an overpopulation
of the tiny insects after the
EWM is gone.
For more information, contact
www.enviroscienceinc.com.
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