Number Resistant Species for Several Herbicide Sites of Action(HRAC Codes) -ACCase Inhibitors(A) -ALS Inhibitors (B) -EPSP Synthase Inhibitors(G) -Synthetic Auxins(O) -PSII Inhibitors(C1,C2,C5) Note:PSII Inibititors Combined 160 140 120 C1,C2,C3 100 80 60 40 20 0 1955 1965 1975 1985 1995 2005 2015 Year Dr.lan Heap,WeedScience.org 2015