Thanks for your inquiry on addressing duckweed.  I assume that you question relates to duckweed growing in your pond? Though duckweed can be viewed as a nusiance, the plant also provides habitat value.  An abundance of duckweed could be a symptom of underlying problems to address such as high nutrients in the water. Thus reducing the input of nutrients into the pond (e.g. fertilizers from nearby uses) should always be explored. High nutrients in ponds also encourages algae growth and related problems from algae. Duckweed shades and call cool the pond.  Thus, treating duckweed can encourage algae growth.  

Mechanical removal of duckweed (e.g. skimming) is often the first management option to consider. By removing the duckweed, you are also removing the nutrients that fuel the growth of duckweed. The duckweed will make good compost or feed for certain animals (e.g. poultry).  Please check that the duckweed is safe for your livestock. 

Chemical control can be complicated and only used if other measures are not meeting your goals.  Chemicals must be applied to regulatory procedures stated on the label and state regulations. Further restrictions on chemical use may also apply to water bodies that connect to other waters, especially streams, and rivers.

Here some resources for you to learn from.

https://extension.psu.edu/duckweed-and-watermeal

This an informative video that includes much of the information I would typically sharing with you.  Note that sharing this link is not an official  endorsement for a specific company or its products. 

Thanks for your inquiry. Please do not hesistate to contact me if I can be of further assistance.

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Samuel S. Chan

Statewide Watershed Health and Aquatic Invasive Species Specialist

Broader Impacts Research Team Leader, NSF Water Sustainability 2100

Sea Grant College Program; Extension Service, Oregon State University

1600 SW Western Blvd. Suite 350, Corvallis, OR, 97330 USA

Cell:<personal data hidden>, FAX:<personal data hidden>

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