In high flow rate situations you can setup a temp. siphon or rent a pump and pump the pond down a few feet prior to Sonar app. We then treat the exposed shoreline with Reward to kill duckweed on the edges. When this has been done SOnar has eradicated 83% (5 out of 6) of the ponds heavily infested with duckweed. We have also eradicated it when the pondowner stays on it with Reward and surfactant at proper rates. Good luck, I hate it for pondowners when all of a sudden they have duckweed and are forced into spending some serious time and money to have their pond back.
