I’ve had fewer pond weed calls this year of any. I was talking with Alan Dennard this morning, and he has noticed the same. Last week, I was asked about algae in a pond. Sometimes these small, floating weeds resemble algae from the road. But this is actually duckweed mixed with watermeal. Both of these weeds are commonly seen together. In the morning, they will cover the entire pond. By afternoon, they float around pushed by wind. Oxygen depletion becomes an issue once these weeds take over a pond. There were no fish in this pond, but if this was eliminated all at once, we’d likely see a fish kill. Both of these weeds tend to grow in quiet, undisturbed water.
Identification
There are different chemical recommendations for each of these weeds; however, there are also compounds that will kill both however. Both are seed bearing plants, but duckweed is separated from watermeal by its roots. Duckweed has 1 to 3 leaves or fronds with a single root hair coming down. Below is a more up close photo:
Duckweed is larger than watermeal
The microscope picture below shows the difference in size between duckweed and watermeal.
Watermeal & Duckweed
Control
We would absolutely need to kill only 1/3 of this at a time (if fish are present). Diquat (Reward) has activity on both weeds, as also does Clipper and Sonar.
Thomas County Ag 