The classification of herbicides by site of action, published in 1997, has been revised. The classification system uses a numbering system for a herbicide's site of action, chemical family, and common name. Regulatory agencies in the United States and Canada have published labeling guidelines based on the classification to aid in herbicide resistance management.
Abbreviations: EPA, Environmental Protection Agency; HRAC, Herbicide Resistance Action Committee; PMRA, Pest Management Regulatory Agency.