There are currently 546 unique cases (species x site of action) of herbicide resistant weeds globally, with 274 species (156 dicots and 118 monocots). Weeds have evolved resistance to 21 of the 31 known herbicide sites of action and to 168 different herbicides. Herbicide resistant weeds have been reported in 102 crops in 76 countries. The website has 3479 registered users and 765 weed scientists have contributed new cases of herbicide resistant weeds. View Recent Additions, Site of Action Summary, or the Herbicide Classification System.