The present invention relates to the use of succinate dehydrogenase inhibitors and/or complex III inhibitors for controlling undesired fungal pathogens and simultaneously improving the ratio of harmful to beneficial microorganisms in crops and to a method for treating crops or parts of crops for controlling undesired fungal pathogens and simultaneously improving the ratio of harmful to beneficial microorganisms by treating the crops or parts of crops with a succinate dehydrogenase inhibitor and/or a complex III inhibitor.