Mark,
The southern variety of pondweed that I'm experienced with does not exhibit the same early summer die back traits that you and Bill both described.
Grass carp, in my experience, prefer new growth on plants and attack new growth on our pond weed vigorously....but they don't do much to old growth pond weed. The Reward seemed to kill back the pond weed including old growth. The pond weed then tried to regrow/regenerate and at that point the newly introduced young grass carp really did a number on it. The southern variety I'm talking about sounds very different from your variety, however.
Is it possible that your original stocking of grass carp, in 04, escaped? If so, the pond weed growth could have taken off during their absence. Seems like your current numbers should get on top of the pond weed this season. I hope they do and you can get away from the use of chemicals.
