Lesions will have pycnidia, but these are difficult to see except by using a 20X lens and looking at lesions by holding diseased leaves up to the light. The difficulty in seeing pycnidia is the result of their light color and the fact that they are buried in the leaf tissue rather than being superficially imbedded, as is the case with S. tritici . Pycnidia of S. nodorum are honey-brown and are almost perfect circles. Individual lesions frequently have pycnidia of both fungi present. Lesions of one or both Septoria fungi can rapidly expand and kill portions of leaves or entire leaves.
Lesions frequently begin from the middle to the tips of leaves.
This is especially true when leaves are damaged due to freezing temperatures or some other physical or chemical factor. When one or both Septoria fungi invade the heads of wheat, the disease is known as glume blotch. Infected glumes will show irregular gray-brown lesions with a purplish border. The infection starts at the tips of the glumes and works its way toward the base. Pycnidia, a diagnostic sign of the disease, will be visible in the lesions using a 10X lens.