The invention relates to novel carboxamides of formula (I), in which M represents a phenyl ring, pyridine ring or pyrimidine, pyridazine or pyrazine ring, respectively monosubstituted by R8, or represents a thiazole ring substituted by R8-A; R8 represents hydrogen, fluorine, chlorine, methyl, isopropyl, methylthio or trifluoromethyl; R8 can also represent methoxy; R8-A represents hydrogen, methyl, methylthio or trifluoromethyl; L1 represents C1-C10 alkene (alkanediyl); Q represents O, S, SO, SO2 or NR9; L2 represents a direct bond, SiR10R11 or CO; R represents hydrogen, C1-C8 alkyl, C1-C8 alkoxy, C1-C4 alkoxy-C1-C4-alkyl, C1-C4 alkylthio-C1-C4-alkyl, C2-C8 alkenyl, C2-C8 alkynyl, C1-C6 haloalkyl, C2-C6-haloalkenyl, C2-C6 haloalkynyl or C3-C6 cycloalkyl; A represents the group of formula (AI); the remaining substituents are defined in claim 1. The inventive substances have a powerful microbicidal action and can be used to control undesirable micro-organisms such as fungi and bacteria in the phyto-protection and material protection fields.