How to Remove Duckweed

Duckweed can be a nuisance. It is thought to be the fastest-growing aquatic plant in existence and can double its coverage area in a matter of days. Furthermore, it is exceedingly difficult to remove. Skimming might temporarily fix the problem, but more than likely, the duckweed will quickly repopulate.

Instructions

How to Remove Duckweed

1. Identify the plant. Not all green pond cover is duckweed, and Diquat does not kill all species of plant weed. If you are unsure, take close-up and wide shots of the pond cover, and take them to your local aquatic herbicide dealer for proper identification.

2. Carefully calculate the required dosage of Diquat you will need. You will need 1 gallon of diluted Diquat solution per surface acre of pond. An acre is 43,560 square feet. Be sure to calculate carefully and adjust for fractions of an acre. Too high a concentration will not kill the duckweed any faster, but it might harm other life in the pond.

3. Dilute the Diquat in water. Fill an appropriately sized container with the required amount of water. Then add the appropriate amount of Diquat in a 50:1 ratio.

4. Fill your pond sprayer with the diluted Diquat solution.

5. Spray the pond. Diquat is a spot treatment herbicide. It should be sprayed directly onto the duckweed. If the duckweed is dispersed, gathering it to one side of the pond (by dragging it with a board or spraying it with the hose) will make your job easier and increase the effectiveness of Diquat.

6. Wait two weeks, then retreat the pond in the same fashion. Repeat at two-week intervals if needed.

Tips & Warnings

• Late spring is the best time of year to apply Diquat. The plants are the most vulnerable during this time. Treating in July or August severely depletes the oxygen level and could kill your fish. If you must treat during these months, only treat one section at a time.

• It is wise to wait a minimum of 24 hours before allowing swimmers to return to a treated pond.

References

• Aquatic Plant Management

Resources

• The Environmental and Health Impact of Aquatic Herbicides