Tordon from you local farm store is about 15$ for a quart bottle (thera abouts) and is some tree killing stuff. I DON"T know if it should be used around a pond though...you'll have to look into that yourself.

It's great stuff, but has the potential to kill off tress within the range of the undesired tree's root system. This has not happened to me except if the surrounding tree/s are of the same species. I once killed several honey locust trees and several more a distance away also died. I didn't mind, those thorny buggars are hateful.

I put the tordon in a spray bottle and just spray the woody portion around the bark area after I cut the tree down. It saves a lot of poison compared to squirting it straight out of the bottle. It does not take much to do the job.

Fish on!,
Noel