The screen is
down out to the edge of the zone of rooted plants,
Be certain to overlap the rolls so that there are no bare spots.
needed.
The
should be examined in about 2 to 3 weeks to reposition stakes and
smooth the screen to the sediment surface.
A poor application will have
missed areas, and extensive "ballooning" or even lift-off of the cover could
occur.
will be a nuisance to boaters and swimmers, and any screen with a
specific gravity less-than 1.0 poses a
to reservoir
if sub-
stantial amounts of it break free and float toward intake structures.
Application is best accomplished during water level drawdown.
Plants
are absent, obstructions can be avoided or removed, and the applicators can
Otherwise, early summer before dense vegetation develops is
see their work.
As Perkins, Boston, and Curren (1980) and
optimum.
(1982) have shown,
screens can be removed after 2 months and placed elsewhere.
The area treated
first (May-June) should remain essentially free of weeds during the remainder
of the summer, and the screen can be used for July-hugust control elsewhere.
Harvesting prior to application should also make the job easier and the cover--
age more complete.
Effectiveness, Costs, and Feasibility
Three materials, Aquascreen (fiberglass), Dartek (nylon), and Typar
received extensive testing and have been shown to be
(polypropylene),
effective in controlling rooted aquatic plants.
The use of these materials is
best described by presenting brief case histories of their use.
The other
materials will also be briefly described.
The reader should consult Cooke
et al. (1986) for other case histories and descriptions of techniques.
Aquascreen
screen coated with polyvinyl chloride.
It resembles window screen.
It is
sold in rolls of 7 by 100 ft, with a mesh size of 62 apertures
at
-1
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.20(1984 prices; Menardi-Southern Division of
or ,000 ha
ter Corporation, Augusta, GA), plus installation
Aquascreen has been shown, in many investigations, to be completely
effective in controlling rooted aquatic plants, at least for the season of
application.
Mayer (1978) fi rst described the use of this product follow
extensive experiments in Lake Chatauqua,
York_.
reported that
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