I agree with Shan. I advise pondowners to hire me for the first treatment with Reward (and take notes), but do it themselves after the first application. You really have to stay on top of it to compeletely eradicate with Reward, but it can be done. The 3% that is not killed will quickly take back over if not retreated.
When using Sonar we will siphon or pump the lake down so the required ppb concentration is maintained for at least a month. It has worked 3 out of 4 times to control duckweed or even worse watermeal.
