The Herbicide Resistance Action Committee (HRAC) classifies herbicides by their mode of action (MoA) to provide a uniform way for farmers and growers to identify the agents they use and better manage pesticide resistance around the world.
[1][2] It is run by CropLife International[3] in conjunction with the Weed Science Society of America (WSSA).
[7] The HRAC give a letter based class to each active constituent herbicide.
In 2021, alternative numeric classes were added, to make codes globally more consistent.
This set of classification changes also added or moved a few herbicides that had been misclassified, and reduced regional concerns that using the English alphabet could be an impediment for international growers.