METHOD FOR INCREASING THE EFFICACY OF A HERBICIDE

A method for increasing the efficacy of a herbicide which comprises applying an aqueous spray liquor of the herbicide in combination with an anionic copolymer CP, where the copolymer CP is made of repeating units of polymerized ethylenically unsaturated monomers M comprising a) 50 to 99.5% by weight, based on the total weight of ethylenically unsaturated monomers M, of at least one monomer Ma selected from the group consisting of primary amides of a monoethylenically unsaturated monocarboxylic acid having 3 to 6 carbon atoms; b) 0 to 50% by weight, based on the total weight of ethylenically unsaturated monomers M, of one or more monomers Mb, where the monomer Mb is either - at least one monomer Mb.1 selected from the group consisting of monoethylenically unsaturated sulfonic acids and the salts thereof; or - at least one monomer Mb.2 selected from the group consisting of monoethylenically unsaturated monomers bearing at least one quaternary ammonium group; and c) 0 to 15% by weight, based on the total weight of ethylenically unsaturated monomers M, of one or more monoethylenically unsaturated monomers Me having at least one poly- C2-C6-alkyleneoxide moiety which has a terminal OH group or a terminal C1-C6-alkxoy group in addition to the moiety bearing an ethylenically unsaturated double bond; where the total amount of monomers Ma and Mb is at least 85% by weight, based on the total weight of ethylenically unsaturated monomers M, and where the total amount monomers Mb and Mc is from 0.5 to 50% by weight, based on the total weight of ethylenically unsaturated monomers M.