Substituted fused heterocyclic herbicides

A compound of the formula ##STR29## wherein X is CH;

• Y is N;
• Z is N or CR.sup.5 ;
• Q is N or CR.sup.5 ;
• R is C.sub.1 -C.sub.4 alkyl, C.sub.2 -C.sub.4 alkoxyalkyl, C.sub.2 -C.sub.4 alkenyl, C.sub.2 -C.sub.4 alkynyl, C.sub.1 -C.sub.4 alkoxy, C.sub.1 -C.sub.4 alkylthio, C.sub.1 -C.sub.3 alkylamino or N(C.sub.1 -C.sub.3 alkyl) (C.sub.1 -C.sub.3 alkyl);
• R.sup.1 is H, F, Cl or CH.sub.3 ;
• R.sup.2 is H, halogen, C.sub.1 -C.sub.3 alkyl, C.sub.1 -C.sub.3 haloalkyl, C.sub.1 -C.sub.3 alkoxy or C.sub.1 -C.sub.3 haloalkoxy;
• R.sup.3 is H, halogen, C.sub.1 -C.sub.4 alkyl, C.sub.2 -C.sub.4 alkenyl, C.sub.2 -C.sub.4 alkynyl, C.sub.1 -C.sub.4 haloalkyl, C.sub.3 -C.sub.4 halocycloalkyl, C.sub.2 -C.sub.4 haloalkenyl, C.sub.2 -C.sub.4 haloalkynyl, OR.sup.6, S(O).sub.n R.sup.7 or CN;
• R.sup.5 is C.sub.1 -C.sub.4 haloalkyl, C.sub.3 -C.sub.5 halocycloalkyl, C.sub.2 -C.sub.4 haloalkenyl, C.sub.2 -C.sub.4 haloalkynyl, OR.sup.6, S(O).sub.n R.sup.7 or halogen;
• R.sup.6 is C.sub.1 -C.sub.4 alkyl, C.sub.3 -C.sub.4 alkenyl, C.sub.3 -C.sub.4 alkynyl, C.sub.1 -C.sub.4 haloalkyl, C.sub.2 -C.sub.4 haloalkenyl or C.sub.2 -C.sub.4 haloalkynyl;
• R.sup.7 is C.sub.1 -C.sub.2 alkyl or C.sub.1 -C.sub.2 haloalkyl;
• and
• n is 0, 1 or 2;
• or their mono N-oxides or their agriculturally suitable salts, provided that:
• (a) when Z is N, then Q is CR.sup.5 ;
• and
• (b) when Q is N, then Z is CR.sup.5.