Disclosed herein are methods of controlling a broadleaf volunteer crop, comprising applying to the broadleaf volunteer crop, an area adjacent the broadleaf volunteer crop, or to soil or water to prevent the emergence or growth of the broadleaf volunteer crop, a herbicidally effective amount of a 6-arylpicoline carboxylic acid, a 2-arylpyrimidine carboxylic acid, or a salt or ester thereof.