Duckweed and Copper Sulfate
Peter Benson
The pond is roughly 100' by 30'. It fills each winter with the rains and
dries out over the summer and fall. The last rains have come and gone and
I do not expect that there will be anymore new water added to the pond.
Thus, no spillage over the embankment.
In the last month, duckweed has covered the surface of the pond. Duckweed
is a small leafed plant, about 1/8" in size. It is not slimy nor does it
stink. It is just VERY green and completely obscures the surface of the
water except when the wind blows patches clear.
I would prefer a pond that had mostly water visible. The consulting
freshwater biologist said I probably would not be able to get a permit for
sterile carp. Instead, he suggest using .5 parts per million of copper
sulfate. He said that it might make the small fish and frogs in the pond
sluggish, but it would not kill them.
I can buy copper sulfate in 50 pound sacks, but I suspect I need about 2
pounds - at most. So here are my questions:
1. what is the consensus of opinion on using sopper sulfate to control
weeds.
2. Where can I get smaller quantities.
--
Peter Benson, Ph.D. | ITT Aerospace/Communications Division
phone: (619)578-3080 | 10060 Carroll Canyon Road
fax: (619)578-5371 | San Diego, CA 92131
email: ben...@acdca.itt.com
brett rowley
Depending on the alkalinity of your water, copper sulfate may or may
not kill your fish. I have found a couple of effective treatments for
duckweed. One is to spray the duckweed with a mixture of one part
liquid dish soap mixed with 100 parts diesel fuel. Spray directly on
top of the duckweed. This works, but requires several treatments before
controlling the weed. It smells bad, especially when the stuff dies,
but is not harmful to any fish. The other is to spray the duckweed with
the herbicide Diquat dibromide at the recommended rate. This is easier
and cleaner, but diquat is a dangerous chemical and must be handled
carefully. Hope this helps.
Brett
BBezdek
Copper Sulphate will not kill duckweed. It is used for algae control, It
can be VERY toxic to fish if used above 1ppm (part per million).
Byron T. Bezdek (Tab)
Aquatic Management
Lisbon, Ohio
bbe...@aol.com
Michael P. Masser
Peter:
Diquat or "Reward" (same chemical) or SONAR are the only FDA
approved chemicals that will work on duckweed. Technically I don't believe
the diesel fuel is legal. Anytime you apply a herbicide you must be
careful that an oxygen depletion (due to the decomposition of the plants
that you killed) does not occur. It is best to apply these chemicals
early in the growing season before while they are in the rapid growth
phase and before the water temperature gets too warm. Also these
chemicals may kill other plants in the pond! Finally grass carp will not
work, they will not consume duckweed in any quantity. Good Luck!