Best way I've found to kill them is cut them flush to the ground in the Fall and immediately paint Tordon RTU on the cut stump. I have some in a small coffee can, and use a 3/4" or 1" wide "chip" brush that you find in the paint dept at the big box stores. The brush is typically under a buck and is of natural hair, steel clamp and a wooden handle. I pour about 1" in the bottom of the can, and leave the chip brush in the can (with the lid on) as I move it around. I waste less brushing it on vs. squirting it on.

$27.00 @ Tractor Supply or $16.95+ shipping from here:
https://www.forestrydistributing.com/tordon-rtu-specialty-herbicide-corteva

www.hoosierpondpros.com

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).