A compound of formula (I): Het is pyridinyl, pyrimidinyl, thiophenyl, furyl, isothiazolyl or isoxazolyl, each being substituted by groups R 4 , R 5 and R 6 ; R 1 is hydrogen or halo; R 2 is hydrogen or halo; R 3 is optionally substituted C 2-12 alkyl, optionally substituted C 2-12 alkenyl, optionally substituted C 2-12 alkynyl, optionally substituted C 3-12 cycloalkyl, optionally substituted phenyl or optionally substituted heterocyclyl; and R 4 , R 5 and R 6 are, independently, selected from hydrogen, halo, cyano, nitro, C 1-4 alkyl, C 1-4 haloalkyl, C 1-4 alkoxy(C 1-4 )alkyl and C 1-4 haloalkoxy(C 1-4 )alkyl, provided that at least one of R 4 , R 5 and R 6 is not hydrogen. The compounds of formula (I) have plant-protective properties and are suitable for protecting plants against infestations by phytopathogenic microorganisms.