Septoria sp. are facultative parasites and survive on straw, seed, volunteer plants, and wild grasses. Causes significant damage in areas where cond itions favor the disease. Occurs on wheat, bromegrass, wheatgrass. Barley has some degree of resistance and oats are immune. Tan spot is increasing as a disease problem in no-till, continuous wheat.
Infection leads to development of tan leaf spots with yellow borders.
Lesions become dark in the center as conidiophore development occurs. Extensive development of pseudothecia may occur on straw and provides abundant primary inoculum. Development and dispersal of inoculum, as well as infection are favored by prolonged periods of wetness. Seedborne inoculum is no t a factor. Yield loss is associated with the degree of damage to the flag leaf.