The present invention relates to the use of ALS inhibitor herbicides for controlling unwanted vegetation in ALS inhibitor herbicide tolerant Beta vulgaris plants, more preferably this invention relates to the use of ALS inhibitor herbicides for controlling unwanted vegetation in areas of growing Beta vulgaris plants, preferably sugar beet, wherein Beta vulgaris, preferably sugar beet, comprises a mutation in codon 1705-1707 of an endogenous ALS gene encoding an ALS protein containing an amino acid that is different from tryptophan at position 569, preferably tryptophan is substituted with leucine.