Why is Hydrilla a problem?
- Makes swimming, boating, fishing, and water skiing difficult and
dangerous - or impossible (people have drowned because of Hydrilla!).
- Hinders commercial navigation
- Clogs water intake systems
- Shades out desirable aquatic plants
- Provides breeding habitat for mosquitoes and other pest.
How to Control Hydrilla
Once Hydrilla becomes established, eradication is often not possible.
The treatment required to control infestations within levels that would
permit continued use of lakes and streams is difficult and expensive.
Herbicides and mechanical harvesters provide some control of Hydrilla,
but both are expensive and regrowth can be rapid requiring repeated
treatments. NOTE: The Catawba Riverkeeper Foundation, Catawba Riverkeeper,
and The Lake Norman Covekeepers DO NOT support herbicides as a control
method!
Herbicides used on Hydrilla:
-
Glyphosate, (a
suspected human carcinogen and mutagen)
-
Diquat, (known
to cause liver damage and cataracts)
-
Copper, (known
human mutagen with varying toxicity to fish)
has also been found to damage aluminum boats and pontoons.
-
Fluridone. (moderate
toxicity to fish and other aquatic organisms)
The most cost-effective, long tern control of Hydrilla is the use of
sterile grass carp, Ctenopharyngodon idella. When this herbivorous
fish is stocked at rates of up to 20 fish per acre of Hydrilla, control
can generally be obtained in one or two years. Once control is
obtained, maintenance stockings of grass carp are required to maintain
control in subsequent years.
Click here for more info about Grass Carp used to control the Hydrilla on Mountain Island Lake.
Whole-lake management of hydrilla with grass carp is certainly
possible, however, the "getting there" will be exceedingly challenging.
An estimate of grass carp management costs of hydrilla on Lake Norman could
easily be based on 160,000 fish (8000 potential hydrilla acres times 20
fish per acre) at $4.00 a fish. Supplemental stocking (~25% of the
original stocking) would be required every two years or so to maintain a
viable weed eating population of grass carp. Management of hydrilla is a
long-term
commitment.
Following a time consuming hydrilla distribution assessment by Lake
Norman's Duke Power's Mosquito Control Teams, hydrilla is now scattered
over approximately 18 square miles of lake surface area. This is an increase of 14 square miles
from last year. The key word is scattered. It is not covering 18 square miles
of lake surface. The plant is growing in individual scattered sprigs,
small clumps to large clumps and complete cove coverage depending on the
location. Click here for Duke Power
Aquatic Plant Management Programs Hydrilla infestation map of Lake Norman.
The photo below shows the mosquito habitat and muck that can be created
by Hydrilla (photo taken at Mountain Island Lake July 2002).
Hydrilla look-alikes
American waterweed = Canadian elodea = Elodea canadensis
Native to the US
Brazilian elodea = Egeria densa
Non-Native to the US
(Anacharis is a term used for all the above)
Comparisons of
the three (this page may load very slow)
Links to Hydrilla information on other sites
Hydrilla
infestation at Lake James
Duke Power
answers Lake James Hydrilla questions
Mountain Island Marine Commission Hydrilla information
University of
Florida - Hydrilla identification and photos
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