GB I think the key is having a good concentration of SOnar for the first thirty days. I try all efforts to increase that chance, draining and watching the weather. If it is going to rain heavy in a week, wait. ALso better to treat before it gets too hot. Kelly Duffie may add a comment on this, but I feel SOnar can work great on Duckweed under the right circumstances, (best way to eradicate). However, I find it hard to believe it will stop duckweed or other invasive plants after about 6 months of the application, much less 5 years, I mean how is it concentrated enough after the pond has received flows for a few months?
