The invention relates to microbicidal silyloxyalkane azoles of the formula I ##STR1## wherein X is the bridge member --CH.dbd. or --N.dbd.,Ar is a phenyl, diphenyl or naphthyl group,R.sub.1, R.sub.2 and R.sub.3 independently of one another are hydrogen, nitro, halogen, C.sub.1 -C.sub.3 alkyl, C.sub.1 -C.sub.3 alkoxy or C.sub.1 -C.sub.3 haloalkyl,R is one of the groups --COOR.sub.5, --COSR.sub.6, ##STR2## or --CN, R.sub.5 is C.sub.2 -C.sub.10 alkenyl which is unsubstituted or substituted by halogen; C.sub.2 -C.sub.10 alkynyl which is unsubstituted or substituted by halogen; or is a C.sub.3 -C.sub.8 cycloalkyl group or a phenyl group which is unsubstituted or substituted by halogen, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy, --CN or --CF.sub.3 ; or is a C.sub.1 -C.sub.12 alkyl chain which from C.sub.2 alkyl may be interrupted by oxygen or sulfur and is unsubstituted or substituted by a member selected from the group consisting of halogen, phenyl, --COO--C.sub.1 --C.sub.4 alkyl, --CO--C.sub.1 --C.sub.4 alkyl, --CO--phenyl, an unsaturated or saturated 5- or 6-membered ring containing oxygen or sulfur as heteroatom, with each phenyl moiety being unsubstituted or substituted by one or more identical or different halogen atoms,R.sub.6 is C.sub.1 -C.sub.10 alkyl, or is a phenyl or benzyl group, each unsubstituted or substituted by halogen, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy, --CN or --CF.sub.3,R.sub.7 and R.sub.8, each independently of the other, are hydrogen, C.sub.1 -C.sub.6 alkyl, C.sub.3 -C.sub.7 cycloalkyl, or a phenyl or benzyl group in each of which the aromatic ring is unsubstituted or substituted by halogen, C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 alkoxy, --CN or --CF.sub.3, or one of R.sub.7 and R.sub.8 is also the --N(R.sub.9)(R.sub.10) group or both taken together form a 5- or 6-membered saturated or unsaturated heterocyclic ring which may additionally contain 1 or 2 further N atoms,R.sub.9 and R.sub.10, each independently of the other, are hydrogen, C.sub.1 -C.sub.4 alkyl or a phenyl radical which is unsubstituted or substituted by halogen, C.sub.1 -C.sub.4 alkyl, --CN or --CF.sub.3 ; andR.sub.4 is the --Si(R.sub.11)(R.sub.12)(R.sub.13) group, wherein each of R.sub.11, R.sub.12 and R.sub.13 independently is a radical selected from C.sub.1 -C.sub.4 alkyl, C.sub.3 -C.sub.7 alkenyl or phenyl, each unsubstituted or substituted by one or more halogen atoms,and the acid addition salts and metal complexes thereof.Also disclosed are methods of preparing these compounds and also pesticidal compositions which contain at least one of the novel compounds as active ingredient. A method of controlling phytopathogenic microorganisms with the aid of the novel compounds of the invention is also described.