+1 The brush blade works great! Unwanted growth is demolished. Only problem is it will come back. I had areas similar to what you are describing and hit them with a 41% glyphosate laced with 2-4-D cocktail first (recommended by the glyphosate manufacturer). I wacked them after they died off. That cocktail is now my go to mix in areas away from the pond.
FWIW Near the pond I use Aqua Neat and it has proven effective. There are several approved herbicides for areas near ponds.
Last edited by Bill D.; 12/20/15 08:46 PM. Reason: Clarification