Thanks for the informative response. I'm not near the pond right now but my buddy is, so if he pulls out a handful of EWM and the ends are green. bushy and healthy looking we need to treat again? If that is the case should we treat now or wait a couple more weeks to make sure?

The EWM that was in small areas is really looking bad, it is the areas that the matt is the thickest that its still looking healthy. Does the size and thickness of the matt have anything to do with it?