The Septoria fungi destroy nearly 2 percent of the world's wheat annually. Actual damage to winter wheat is difficult to measure under field conditions because tan spot and leaf rust commonly occur simultaneously with Septoria within fields. Average annual losses amount to around 5 percent in Nebraska, but have been as high as 30 percent in individual fields because of foliar diseases. Symptoms Figure 2. Septoria pycnidia on leaf lesion.
Symptoms appear first as small, chlorotic flecks restricted by veins.
These specks are pycnidia, the spore-producing bodies of Septoria fungi. The presence of pycnidia is the most reliable field sign for distinguishing Septoria leaf blotch from other leaf spot diseases. The disease may also develop on leaf sheaths and stems, especially at the nodes, and occasionally on the tips of glumes. In the fall, wheat becomes infected during periods of wet, cool weather. Heavy fall infection retards root development which can aggravate losses in stand to crown and root rot.