This work aimed to evaluate the effectiveness of herbicides applied during post-emergence on weed control in onion crop that recently have infested the onion crop areas in Monte Alto city, São Paulo state, Brazil. Fourteen herbicides, either alone or in mixture, were tested to control Sisyrinchium micranthum Cav. and an unidentified specie of the genus Agrostis. The herbicides used were: flumioxazin, bentazon + ioxynil + oxyfluorfen, fluazifop-p-butyl, fluazifop-p-butil + ioxynil, fluazifop-p-butil + oxyfluorfen, paraquat + oxyfluorfen, paraquat + fluazifop-p-butil + […]