A fungicidal compound of formula (1): where Het is a 5- or 6-membered heterocyclic ring containing one to three heteroatoms, each independently selected from oxygen, nitrogen and sulphur, the ring being substituted by groups R7, R8 and R9; R1 is hydrogen, optionally substituted (C1-4)alkylC(═O), optionally substituted (C1-4)alkylC(═O)O, optionally substituted (C1-4)alkoxy(C1-4)alkyl, optionally substituted allyl, optionally substituted propargyl or optionally substituted allenyl; R2, R3, R4and R5 are each, independently, hydrogen, halogen, optionally substituted (C1-4)alkoxy(C1-4)alkoxy or optionally substituted (C1-4)alkoxy(C1-4)alkyl; R6 is an organic group containing three to thirteen carbon atoms and at least one silicon atom and, optionally, one to three heteroatoms, each independently selected from oxygen, nitrogen and sulphur, and is optionally substituted by one to four independently selected halogen atoms; R7, R8 and R9are each, independently, hydrogen, halogen, C1-3alkyl, C1-3haloalkyl, C1-3alkoxy(C1-3)alkyl or cyano, where at least one of R7, R8and R9 is not hydrogen; and X is O or S; or an N-oxide thereof; and when present, each optional substituent on alkyl moieties, allyl, propargyl and allenyl is, independently, selected from halogen, hydroxy, cyano, methoxycarbonyl, ethoxycarbonyl, methoxy, ethoxy, methylsulfonyl, ethylsulfonyl, diflouromethoxy, trifluoromethoxy and trifluorothiomethoxy.