Septoria tritici Roberge in Desmaz.
Phaeosphaeria nodorum (E. Müller) Hedjaroude [teleomorph]
Stagonospora nodorum (Berk.) Castellani & E.G.Germano [anamorph]
Phaeosphaeria avenaria (G.F. Weber) O. Eriksson f. sp. triticea T. Johnson [teleomorph]
Stagonospora avenae (A. B. Frank) Bissett f. sp. tritica T. Johnson [anamorph]
- Symptoms: Initial infection sites tend to be irregular in shape, oval to elongated chlorotic spots or lesions. As these sites expand, the centers of the lesions become pale, straw colored, and slightly necrotic, often with numerous small black dots (pycnidia) (Picture at left). The lesions of septoria blotch tend to be linear and restricted laterally (Picture on right), while those of stagonospora blotch (Picture at bottom left) are more lens shaped. All above ground plant parts can be affected. Light infection produces only scattered lesions, but heavy infection can kill leaves, spikes (Picture at bottom right is stagonospora blotch), or even the entire plant. Identification of species in the field can be difficult, and microscopic examination is often necessary.
- Development: Initial infections tend to be on the lower leaves, progressing to the upper leaves and spikes if environmental conditions remain favorable. Cool temperatures (10-15ºC) and prolonged wet, cloudy weather favors the development of these diseases.
- Hosts/Distribution: These are primarily diseases of wheat, but other cereals are somewhat susceptible. The diseases are limited to temperate wheat-growing areas where cool and moist conditions prevail.
- Importance: Major losses can occur, through seed shriveling and lower test weights, if these diseases reach severe levels prior to harvest.