Abstract: Compounds of formula I are suitable for controlling and preventing infestation by microorganisms, insects and acarina on plants ##STR1## and their possible isomers and mixtures of isomers, whereina) X is CH.sub.2 F or CHF.sub.2,Y is CH andZ is OCH.sub.3, orb) X is CH.sub.2 F or CHF.sub.2,Y is a nitrogen atom andZ is OCH.sub.3 or NHCH.sub.3,and wherein R.sub.1 and R.sub.2 are each independently of the other hydrogen, cyano, C.sub.1 -C.sub.12 alkyl, halo-C.sub.1 -C.sub.12 alkyl, C.sub.2 -C.sub.12 alkenyl, C.sub.2 -C.sub.12 alkynyl, C.sub.3 -C.sub.6 cycloalkyl, cyclopropylmethyl, C.sub.1 -C.sub.4 alkoxy, C.sub.2 -C.sub.12 alkoxyalkyl, C.sub.1 -C.sub.4 alkoxycarbonyl, C.sub.1 -C.sub.4 alkylthio, C.sub.2 -C.sub.