Leptosphaeria maculans (anamorph Phoma lingam) is a fungal pathogen of the phylum Ascomycota that is the causal agent of blackleg disease on Brassica crops. Symptoms of blackleg generally include basal stem cankers, small grey lesions on leaves, and root rot. The major yield loss is due to stem canker. The fungus is dispersed by the wind as ascospores or rain splash in the case of the conidia. L. maculans grows best in wet conditions and a temperature range of 5-20 degrees Celsius.
Symptoms generally include basal stem cankers, small grey oval lesions on the leaf tissue and root rot (as the fungus can directly penetrate roots).