Herbicidal mixtures containing picloram were more effective than 2,4-D amine for injection of highly resistant species. Good kills were obtained with mixtures of 2,4-D + picloram or 2,4-D + 2,4,5-T + picloram. These mixtures were effective when applied undiluted in a 2-ml dose at 7- to 9-inch intervals around the tree, except that on dogwood the maximum effective spacing was 5 inches.
Peevy, Fred A. 1972. Injection treatments for controlling resistant hardwood species. In: Proceedings 25th Annual Meeting Southern Weed Science Society. Champaign, Illinois: Weed Science Society of America. p. 252-256.