There are currently 530 unique cases (species x site of action) of herbicide resistant weeds globally, with 272 species (155 dicots and 117 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 100 crops in 72 countries. The website has 3291 registered users and 698 weed scientists have contributed new cases of herbicide resistant weeds. View Recent Additions, Site of Action Summary, or the Herbicide Classification System.