(Eurasian watermilfoil) and Potamogeton
leafed pondweed) infestations decayed in 2 to 3 weeks following
The -deposition of sediment on the screen was
after 2 to 3 years of
and this permitted regrowth of the plants.
Mayer found that
autumnal removal of the screens and reposit oning in the spring maintained
95-percent control of nuisance weeds.
Curren (1980) examined the relationship between
Perkins,
coverage time by Aquascreen and control of Eurasian watermilfoil.
Panels that
measured 30 by 80
(9 by 24
were set out in shallow (0.5 to 2.0 m) and
deep (2 to 3
areas of
and then removed at
and
3-month intervals.
Compared with control areas, panels in place for 1 month
produced
and 35-percent decreases of biomass in shallow and deep plots,
and plant regrowth was small.
Two months of coverage produced
and
56-percent decreases in standing crop of plants and little regrowth.
Three
months
coverage essentially eliminated the plants.
Both Perkins, Boston,
and Curren (1980) and
(1982, 1984) found that
was most
effective when applied tightly to the sediment surface.
Growth will occur
emphasizes that screens left in position
under loosely applied screen.
for a second season will have plant growth on them. The screens should be
removed, cleaned, and repositioned.
Similar conclusions were made about
Aquascreen by Lewis, Wile, and Painter
following experiments in an
and Trvelson (1984) reported an average period of plant
Ontario lake.
control in British Columbia lakes to be 2 years.
The screen was found to
allow some plants to grow through it, while fragments of some plants were able
to root through it.
and Trvelson (1984) have found that vinyl-coated window screen
is a satisfactory and less expensive substitute for Aquascreen.
Dartek
Dartek is a black-pigmented, impermeable nylon sheeting material
(DuPont, Canada) with a specific gravity greater than
It is sold in
by 30.5-m rolls (about ,000
(1983 prices).
Perkins (1984) evaluated
the effectiveness of Dartek in Green Lake, Washington, where one roll was
placed over soft unconsolidated organic muck that supported a population of
Four panels of Dartek were
in Lake Washington over
Sheeting without gas-venting slits and those with
sand-gravel sediments.
diagonal slits lifted off the sediments.
Panels that had 12 cross-hatch slits
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