The present invention relates to methods for enhancing the herbicidal activity of 2-((3-(2-chloro-4-fluoro-5-(3-methyl-2,6-dioxo-4-(trifluorometh yl)-2,3-dihydropyrimidin-l(6H)-yl)phenoxy)pyridin-2-yl)oxy)acetic acid, methyl 2-((3-(2- chloro-4-fluoro-5-(3-methyl-2,6-dioxo-4-(trifluoromethyl)-2,3-d ihydropyrimidin-1(6H)-yl)phenoxy)pyridin-2-yl)oxy)acetate, and ethyl [3-[2-chloro-4-fluoro-5-(1-methyl-6- trifluoromethyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-3-yl)phen oxy]-2- pyridyloxy]acetate and to methods for controlling volunteer glyphosate-resistant corn comprising applying synergistic mixtures of 2-((3-(2-chloro-4-fluoro-5-(3-methyl-2,6-dioxo-4-(trifluorometh yl)-2,3-dihydropyrimidin-1(6H)-yl)phenoxy)pyridin-2-yl)oxy)acetic acid, methyl 2-((3-(2-chloro-4-fluoro-5-(3-methyl-2,6-dioxo-4-(trifluorometh yl)-2,3-dihydropyrimidin-1(6H)-yl)phenoxy)pyridin-2-yl)oxy)aceta te, ethyl [3-[2-chloro-4-fluoro-5-(l-methyl-6-trifluoromethyl-2,4-dioxo-1 ,2,3,4-tetrahydropyrimidin-3-yl)phenoxy]-2-pyridyloxy]acetate, or a combination thereof and glyphosate, or a salt thereof, to an area where volunteer glyphosate-resistant corn is growing.La presente invención se refiere a métodos para incrementar la actividad herbicida del ácido 2-((3-(2-cloro-4-fluoro-5-(3-metil-2 ,6-dioxo-4-(trifluorometil)-2,3-dihidropirimidin-1(6H)- 11)fenoxi)piridin-2-ipoxpacetico, 2-((3-(2-cloro-4-fluoro-5-(3-met il-2,6-dioxo-4-(trifluorometil)-2,3- dihidropirimidin-1(6H)-11)fen oxi)piridin-2-11)oxpacetato de metilo y [3-[2-cioro-4-fluoro-5-(1- metil-6- trifluorometil-2,4-dioxo-1,2,3,4-tetrahidropirimidin-3-il )fenoxi]-2-piridiloxijacetato de etilo, y a métodos para controlar el maíz voluntario resistente a glifosato, que comprenden aplicar mezclas sinérgicas de ácido 2-((3-(2-cloro-4-fluoro-5-(3-metil-2,6-dioxo-4-(trifluorometil)-2 ,3-dihidropirimidin-1(6H)-ipfenoxi)piridin-2-11)oxpacetico, 2-((3-(2-cloro-4-fluoro-5-(3-metil-2,6-dioxo-4-(trifluorometil)- 2,3-dihidropirimidin-1(6F0-11)fenoxi)piridin-2-ipoxpac
