The invention relates to the use of the succinate dehydrogenase inhibitor Fluopyram, for controlling Leptosphaeria maculans in Brassicaceae plants, plant parts thereof, plant propagation material or the soil in which Brassicaceae plants are grown or intended to be grown, to a method for treating plants or plant parts for controlling Leptosphaeria maculans and to a method for treating seed for controlling Leptosphaeria maculans in the seed and in the plants which grow from the seed, by treating the seed with the succinate dehydrogenase inhibitor Fluopyram.