There are two species causing stem canker, namely:
- Leptosphaeria maculans (Desm.) Ces. et de Not.
- Leptosphaeria biglobosa (Shoemaker i Brun 2001).
Taxonomic affiliation of those fungi goes as follows:
- Order: Pleosporales
- Class: Dothideomycetes
- Subphylum: Ascomycotina
Those species are different as far as morphological, biochemical and genetic features are concerned as well as in pathogenicity. L. maculans is considered to be more pathogenic, because it may cause a total plant necrosis whereas L. biglobosa usually results in extensive, but superficial spots on the stem.