I've killed hundreds and hundreds of those bastards through my management plan in west virginia. Straight Garlon 3a. No mixing . Fill up some squirt bottles, take a hatchet and and hatchet around the tree and immediately squirt or two in each hatchet wound. I spaced hatchet wounds every 3 inches apart around the diameter. About chest height. Killed some large trees also. Total kill. Then following year early summer come thru with backpack sprayer full of gly and spray the foliage on the little bastards that are still there. I killed off a hell of grove. I hate those things lol. Good luck.