The disease is caused by fungi of the genus Septoria and related species, which infect all above-ground parts of plants. Light beige or grey-brown spots form on leaves and stems, and black dots, known as pycnidia, develop on their surface over time. The disease is dangerous in temperate climates with high humidity and frequent rainfall.
Pathogen development depends on weather factors, particularly temperatures in the range of +15…+25 °C and air humidity above 80%. The disease leads to a reduction in the photosynthetic area, grain shriveling, and a decline in baking quality. The level of loss varies from 10–15% in normal years to 50% during epiphytotics.
Varietal resistance is divided into vertical, based on specific Stb genes, and horizontal, which is considered more long-lasting. Horizontal resistance is determined by morphological characteristics: cuticle density, pubescence, the presence of a waxy bloom, and lack of sensitivity to fungal toxins.
Resistance evaluation in variety trials is conducted using infectious-provocative backgrounds, visual assessment of the degree of infection, and laboratory methods, including molecular diagnostics. The obtained data are compared with reference indicators to determine the effectiveness of variety protection under specific conditions.