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Duckweed Solution Center

Duckweed Frequently Asked Questions

Q.  If I use aquatic weed and algae control products will they harm my fish, pets or the local wildlife?
A.  Herbicides labeled for aquatic use are non-hazardous to fish, pets and the local wildlife when used in accordance with the product label.  Problems, should they occur, are caused by misuse of herbicides, such as:
• Exceeding recommended label rates
• Exceeding application recommendations
• Using products not labeled for aquatic use
Q.  How can I tell if I have algae or duckweed?
A.  There is a simple test: submerge your hand in the plant matter.  If the mass separates, it is probably duckweed or watermeal.  If the mass does not separate, it is probably algae.  Algae is usually slimy and stringy and forms mats on the surface of the pond.  Duckweed appears to form mats, but is a system of small plants the size of pencil erasers that float on the surface of the water.  Duckweed resembles clovers floating on the surface of the water and has small white roots hanging from the bottom of the plant.
Q.  Are there any other treatment options for duckweed besides Sonar?
A.  While the selective, systemic action of Sonar is the most cost-effective, long-term solution to control duckweed, contact herbicides may provide a quick burn-down on those plants with which they come into contact. In addition, contact herbicides may affect native vegetation and can lead to oxygen depletion and fish kills due to the rapid decay of treated vegetation.  Physical removal of the tiny plants is virtually impossible and fish such as grass carp and koi will eat duckweed but will generally consume other aquatic plants first.
Q.  How do I know if I have duckweed on my pond?
A.  If you’re not sure what kind of aquatic vegetation you’re dealing with, utilize the LakeLawnandPond.com Weed Identification interactive page for assistance.
Q.  What’s the best way to prevent duckweed from returning?
A.  Prevention is the key to avoiding costly control measures to eliminate a nuisance duckweed problem. Nutrient reduction and getting some motion in the water through a technique such as bubble aeration are two key preventative techniques. If duckweed does reappear, it is much easier to control the tiny emerging plants than the mature plants; so the best time to take action is at the first sign of infestation.
Q.  Where did all this duckweed come from?
A.  Duckweed is moved from pond to pond by animals and waterfowl such as ducks and geese.  Once duckweed is introduced into a waterbody, it can spread rapidly if conditions are right.  Ideal growing conditions are still or slow-moving water that is high in nutrients such as nitrogen and phosphorous.
Q.  How can I tell if I have algae or duckweed?
A.  There is a simple test:  submerge your hand in the plant matter.  If the mass separates, it is probably duckweed or watermeal.  If the mass does not separate, it is probably algae.  Algae is usually slimy and stringy and forms mats on the surface of the pond.  Duckweed appears to form mats, but is a system of small plants the size of pencil erasers that float on the surface of the water.  Duckweed resembles clovers floating on the surface of the water and has small white roots hanging from the bottom of the plant.
Q.  I have a "green scum" on my pond; what is it?
A.  Green water or "scum" on the top of your water can be any of several things: duckweed, watermeal, or algae.  Frequently these are mistaken for each other.  Duckweed are very small floating leaves with a small root while watermeal resembles green sand.  Filamentous algae form dense mats that float on top of the water and planktonic, or blue-green algae, give water a 'pea soup' consistency.

Sonar* A.S.

Sonar A.S., a liquid herbicide, provides selective control of undesirable aquatic weeds for a year or longer.  Sonar A.S. is your best choice for controlling duckweed, watermeal and many other undesirable plants in ponds with soft or muck bottoms.

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Sonar* A.S.
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