Duckweed Control

Duckweed is a free-floating, tiny aquatic plant that provides low levels of dissolved oxygen for fish and helps shade ponds. But when the population of duckweed explodes, it can completely shade out submerged plants and cause fish kills.

Duckweed relies on heavy nitrogen inputs to survive. Avoid fertilizing the pond, and don't use fertilizers or keep composting materials near the pond where they might run down into it during a rainstorm. Do not overstock the pond with fish or other aquatic life, since wastes are heavy in nitrogen. Remove excessive debris from the pond with a net.

The simplest removal method, especially for smaller ponds, is to scoop as much of the duckweed out of the pond as possible. Finely woven nets at the end of long handles work well, especially if the wind has pushed the duck weed to one side of the pond. Duckweed is a fantastic source of nitrogen for compost piles.

This is by far the most expensive and timing-crucial option. Aquatic herbicides that contain Diquat or Fluridone are effective duckweed controls, but you must use products that are specifically labeled for duckweed to avoid serious harm to your aquatic system. Use exactly as specified on the labels to ensure duckweed control. Several applications may be necessary. Restrictions on water use may apply 24 to 72 hours after application to avoid contamination or poisoning.