Roundup (glyphosate) is available in a formulation that is labeled for use around ponds. I get it at the farm store. There are various trade names, but one is Shore Klear. I have used it frequently on small willows and it works well. Best to apply in the early fall when the plants are drawing the nutrients out of the leaves down to the roots. Beware, it will kill the grass around the willows also. The Remedy will spare the grass.
