A method is disclosed for controlling the growth of undesired vegetation in a plantation crop by applying to the locus of the crop an effective amount of a compound of formula I ##STR1## and A, R.sup.1, R.sup.2, R.sup.3, R.sup.4, X, Y and Z are as defined in the disclosure. Also disclosed are novel substituted heterocyclic compounds and their agriculturally suitable compositions which are generally useful as herbicides, as well as methods of their use as general or selective preemergent or postemergent herbicides, or as plant growth regulants.