Pyridine derivatives of the formula ##STR1## where R.sup.1 is alkylideneaminoxy which is unsubstituted or monosubstituted or disubstituted by alkoxy, alkylthio or phenyl, cycloalkylideneaminoxy which is unsubstituted or monosubstituted or disubstituted by alkyl, succinyliminoxy or azolyl which is unsubstituted or monosubstituted or disubstituted by alkyl or halogen, R.sup.2 and R.sup.3 are each alkyl, haloalkyl, alkoxy, haloalkoxy or alkylthio, R.sup.4 is hydrogen, halogen, alkyl, haloalkyl or alkoxy, and Z is nitrogen or the methine group, and their use for combating unwanted plant growth.