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
