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-(trifluoromethyl)-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-dihydropyrimidin-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)phenoxy]-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-(trifluoromethyl)-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-(trifluoromethyl)-2,3-dihydropyrimidin-1(6H)-yl)phenoxy)pyridin-2-yl)oxy)acetate, 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.
