The present invention relates the use of the compounds of the formula I or the N-oxides, or the agriculturally acceptable salts thereof for combating phytopathogenic harmful fungi, wherein the variables are defined as given in the description and claims. Further present invention relates to novel compounds, to mixtures comprising at least one such compound of the formula I and at least one further pesticidally active substance selected from the group consisting of herbicides, safeners, fungicides, insecticides, and plant growth regulators; and to agrochemical compositions comprising at least one such compound of the formula I and to agrochemical compositions further comprising seeds.