There are currently 514 unique cases (species x site of action) of herbicide resistant weeds globally, with 262 species (152 dicots and 110 monocots). Weeds have evolved resistance to 23 of the 26 known herbicide sites of action and to 167 different herbicides. Herbicide resistant weeds have been reported in 94 crops in 71 countries. The website has 2954 registered users and 628 weed scientists have contributed new cases of herbicide resistant weeds. View Recent Additions, Site of Action Summary, or the Herbicide Classification System.