Triclopyr (3,5,6-Trichloro-2-pyridinyloxyacetic acid) is an organic compound in the pyridine group that is used as a systemic, foliar herbicide and fungicide. It is used to control broadleaf weeds while leaving grasses and conifers unaffected or to control rust diseases on crops.
Triclopyr is effective on woody plants and is used for brush control in rights of way and defoliation of wooded areas. It is also used for broadleaf weeds, particularly Creeping Charlie (Glechoma hederacea).
Triclopyr is formulated both as an ester and as an amine salt. The usual tradeoffs regarding effectiveness, drift, and toxicity to humans apply to these two formulations. It is chemically very similar to the herbicide which it generally replaces, 2,4,5-T, which was phased out in the U.S. in the 1970s amid toxicity concerns.