Leptosphaeria spp. (anamorphic Phoma spp.) is a fungus of the Ascomycetes group. Symptoms mostly include basal stem rot, small grey leaf lesions and root rot. The most significant yield loss is caused by diseased stems. The fungus is dispersed in the form of ascospores by the wind or, in the case of conidia, by rain splash. Leptosphaeria species grow best in wet conditions and a temperature range of 5 – 20 degrees Celsius, Crop rotation, removal of stubble, application of fungicide and crop resistance are important control methods. The fungus can also occur on the seeds of various crops. The fungus is an important pathogen of Brassica crops. Seed treatment can protect seedlings against very early infection by the fungus.