Compounds of formula (I), wherein G represents together with the two carbon atoms of the pyrimidine ring to which it is attached, a 5- to 7-membered aliphatic carbocyclic or heterocyclic ring system which contain 0 to 2 heteroatoms selected from the group consisting of nitrogen, oxygen and sulfur; and wherein said 5- to 7-membered aliphatic carbocyclic or heterocyclic ring system can be mono-, di- or trisubstituted by substituents selected from the group consisting of halogen, keto, C1-C6alkyl, C1-C6alkoxy, C1-C6alkyloximino and C1-C6alkylendioxy; and wherein the other substituents R1, R2, R3, R4, R5 and R6 are as defined in claim 1, and their use as microbicides.