It is nice to be able even think
about weed control in stock ponds; however because of the wonderful rainfall we
have recently received has filled some of our tanks in the area. Even though treating earlier would be better
it is not too late to think about pond management. With the runoff of rains our tanks are sure
to show new plant growth. I came across
this article that Dr. Michael Masser, Texas A&M AgriLife Extension Service
fisheries specialist wrote a couple of years back and thought it would be
important for pond owners this year.
"Aquatic
vegetation are the 'yin and yang of ponds," said Dr. Masser. "It
would be nice to have some aquatic plants for esthetics and wildlife, but too
many are a nightmare."
But
control of moss and other aquatic plants need not be expensive or complicated,
he said. Such vegetation can be controlled by mechanical, biological or
chemical methods – either singly or in combination – in an integrated pest
management approach.
Pond
moss and aquatic weeds can not only turn a pleasant day of fishing into a
perpetual snag, they can make swimming and boating impossible too.
"Ten
to 15 percent pond coverage of rooted aquatic vegetation would probably be good
from a fish and wildlife standpoint, but ponds typically start out with almost
none and after a very few years are almost entirely covered," he said.
There's
a misconception, Masser said, that ponds and lakes can't be cleared of all
rooted vegetation without critically reducing the food chain. True, plants are
the beginning of any food chain, he said, but rooted vegetation tends to take
over small ponds.
Too
many rooted plants not only disrupt recreational activities, but also increase
sedimentation, disrupt the oxygen balance and prevent largemouth bass from
finding prey fish, such as sunfish.
And
also contrary to popular belief, bass do not need rooted vegetation to spawn.
"No,
actually bass have to remove weeds to build their nests," Masser said.
"In fact, scientific research has shown that the most productive bass and
sunfish ponds are actually those that have little or no rooted aquatic
vegetation and instead have green water or planktonic algae blooms."
Other
research has shown that the same stringy, filamentous algae – what most would
call "pond scum" – produces a more constant food supply than rooted
vegetation, he said.
Counter
intuitively, one of the easy ways to prevent root vegetation from taking over a
pond is to fertilize, he said.
"Note,
that I said ‘prevent’ not ‘control,’" Masser said. "Proper
fertilization creates green planktonic algae blooms. The algae blooms shade the
pond bottom in areas over 2 or 3 feet deep and keep rooted weeds from getting
started along the bottom."
Because
fertilizing promotes algae growth, it also builds the food chain and enables
the pond to support more fish, he noted.
An
option is to use non-toxic chemical dyes to shade the pond bottom. The dyes do
not promote green algae growth as does a fertilization program, however. So the
treatment will promote higher fish populations.
There
are mechanical methods to control rooted vegetation, but they all require
considerable industriousness on the part of the pond owner, Masser said. Weeds
can be pulled or grubbed by hand or hoe. Some suppliers of mechanical cutters
use a sickle wire or blade to shred the weeds. The cutters are usually
hand-held and are labor-intensive. And like a home lawn, the vegetation is
continually growing, so cutting has to be done again – and again. The heavy,
water-laden cuttings have to be removed from the pond.
"If
you like mowing your lawn, you're going to love mowing your pond," Masser
said.
There's
only one biological method of pond weed control in Texas: the triploid grass
carp, he said.
Sometimes
called the white amur, grass carp eat most submerged aquatic weeds. They cannot
eat weeds that are on or project above the water surface, such cattails and
lily pads.
Because
it is feared the species might take over ponds and streams and crowd out game
fish, only sterile, triploid grass carp are legal.
To
purchase the fish, pond owners must get a permit from the Texas Parks and
Wildlife Department. The species is only legally available from certified
dealers.
Though
sterile, the grass carp live as long as 10 years. Typically, Masser said, they
control weeds for five to seven years, but are not effective for all species of
weeds.
"This
type of biological control is inexpensive from the standpoint of labor and
chemical costs," Masser said. "Many pond owners, after years of
frustration of trying to control aquatic weeds by other means, have found grass
carp to be a simple and effective answer to their problems if stocked in
sufficient numbers."
And
then there's chemical control, Masser said. The U.S. Environmental Protection
Agency has registered only nine active herbicide ingredients for aquatic weed
control. All have been extensively tested and are safe if properly used.
"However,
many of these herbicides still have water-use restrictions of a few days to
several months for uses like livestock watering, fishing, swimming and
irrigation that may make them unacceptable to many pond owners," Masser
said.
And
there is also the risk of killing too many weeds too fast with chemical
controls. Rapid decomposition of plant material in a small pond or lake can
cause oxygen depletion and kill fish.
Masser
offered these guidelines when using chemical controls.
–
Treat early in the year, April or May.
–
Treat a small section of the pond – about a quarter at most – at one time.
–
Allow time for the decomposition process to complete before treating the next
section.
–
Follow herbicide labels that state the entire pond must be treated at once to
get effective control.
–
Always read and follow label instructions to letter.
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