I used Sonar on my 3 1/2 acre pond which had a heavy lily pad problem and it killed them all, along with all the coontail and Eurasian milfoil.
In short it cleaned my pond out of all vegetation which happens to be what I wanted because it was a mess. I highly recommend it. Be careful though because massive plant kills result in heavy nutrient release and could cause fish kills. Reward works pretty well on water lilies in local areas. You have to use a sticking agent and high concentrations to overcome the waxy barrier on the leaves so that it will be absorbed(Reward is basically Roundup by the way).

Layton Runkle