Duckweed & Watermeal By: Heath Spence, Aquatic Biologist

Duckweed and Watermeal

     Does your pond resemble a putting green?  Your pond may be infected by Watermeal and Duckweed.  These are tiny free-floating plants that can reach nuisance levels very quickly.  Their rapid reproduction ability can quickly cause a pond to be completely covered in only a few weeks. Why may this be disastrous for your pond?  Not only aesthetically unappeasing, but complete coverage may cause summer fish kills.  Once a pond is covered the photosynthesis process is unable to be completed, resulting in lethally low oxygen levels.

             In two weeks, under ideal conditions, a single plant can produce up to 17,500 new plants.

• Both duckweed and watermeal require nutrient rich pond conditions for them to thrive.
•  Well-shaded ponds, protected from heavy winds may also prove to be ideal habitats for infestation.
•  Older ponds with considerable build up of organic matter that has not been broken down efficiently provide the necessary nutrient load for rapid reproduction of these plants.

 So now that these plants have control of your pond, how do you regain control?  The use of several different management techniques is suggested, some being more effective than others.  Prevention and control methods are key strategies in keeping your pond well managed.

•  Reduction of internal and external nutrient loads that are influencing your pond for example; lawn and agricultural fertilizers, waterfowl, leaves and faulty septic systems. 
•  Also the addition of aeration can play a key role in the reduction of nutrient levels
•  Manual removal may reduce some of the growth but will prove to be very labor intensive.

       The pond will most likely be recovered within weeks due to their explosive reproduction.

•  White amurs, Koi and Tilapia and some ducks may eat these plants, however they usually are unable to keep up with the rapid reproduction and will also add to the nutrient load of your pond by defecation.
•  The most reliable and long term control for these plants would be with either Fluridone (tradename of Sonar) or Flumioxazin (tradename of Clipper) applications.

     Duckweed and watermeal have been found to be a serious problem to Ohio ponds.  They are easily transported by waterfowl from one pond to another and since they are free floating they easily can move to your pond from upstream.  Once these plants are introduced and your pond fits the ideal habitat, say goodbye to your pond as you know and love it.  But there is hope! Contact AQUA DOC and allow one of their aquatic biologists to put together a management program for your pond.