Aquacide — Q & A - What aquatic herbicide will kill duckweed in a pond


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Q & A - Started Getting Duckweed Last Year - Suggestions?

Published by Jamie Markoe on December 27, 2013 0 Comments


A customer recently contacted us regarding weeds. Below is the question and our response.


Was given your company name by a previous customer of yours. I have a ¾ acre pond with max depth of about 20 feet. Started getting Duckweed last year with complete cover by late summer. This year already really bad and about ½ covered. Suggestions, costs and application instructions appreciated. I also have filamentous Algae but typically am able to control it with copper sulfate. Some weeds, but quite honestly they provide great breeding grounds and cover for fish. Thanks.

SC, Caseyville, IL


Restore Liquid and Weedtrine-D Liquid are 2 great options for Duckweed control.

Restore Liquid is a systemic option that must be applied to the entire pond and cannot be used for spot treatment. Restore Liquid will not affect filamentous algae but may also affect the weeds in your pond.

A ½ acre pond with a 20’ maximum depth is 21,780 sq. ft. with an average 10’ depth or 5 acre-feet. A pond this size would require 32 oz. of Restore Liquid per treatment. For best results, mix 10.5 oz. of Restore Liquid with enough water to spray evenly over the pond surface. Wait 14 days, mix the second 10.5 oz. of Restore Liquid with water and spray over pond surface. Again, 14 days later apply the final treatment of 10.5 oz. of Restore Liquid mixed with water. Normally, one 3-part application is all you need. Consistent concentration at the treatment site will insure maximum results.

Weedtrine-D Liquid is a fast-acting contact option that can be used for spot treatment or treatment of the entire pond. For best results, mix 15 oz. of Weedtrine-D Liquid with enough water to make 3 gallons of solution and top with 3 oz. of Cygnet Plus Liquid (surfactant). Three gallons of solution will treat 1,000 sq. ft. (100’ x 10’).  A ½ acre pond covered with Duckweed would require 2.5 gallons of Weedtrine-D Liquid and 2-quarts of Cygnet-Plus Liquid.  Repeat treatment may be needed to make good contact with all the small particles of Duckweed. Weedtrine-D Liquid may also affect both filamentous algae and weeds in your pond.

Please feel free to e-mail me or post questions you may have and I will respond accordingly.

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