No. 4/April 17, 1998
Septoria Leaf Blight of Wheat
With the return of warmer weather to much of Illinois, farmers are beginning to notice discolorations of the lower leaves on wheat crowns. Many of these changes are normal physiological reactions of the plant to winter weather, but some are due to the presence of the Septoria fungus.
Septoria diseases of wheat are common throughout southern and, in some years, central Illinois. These diseases are typically not an economic problem unless the infections occur on the flag leaf or the leaf directly below the flag. Septoria diseases appear to have overwintered well this year due to lack of cold weather. So it's not unexpected to see plants affected by the disease.
Septoria leaf blight (or blotch) is characterized by light brown, lens-shaped lesions on the older leaves. The centers of these lesions may have dark black specks embedded in them. The specks are the fruiting structures of the fungus. The lesions themselves are usually light yellow in color initially and then turn brown as the lesions age and the tissues die. Some lesions may lie along the leaf edge and appear as long brown streaks.
Control of Septoria leaf blight at this time is not recommended, given the cost and a lack of economic return. Several fungicides are labeled, but their use should be directed toward protecting the flag leaf rather than the early crown leaves. Examine the new growth; if these leaves are green and healthy, no management is needed.
H. Walker Kirby, (firstname.lastname@example.org), Extension Plant Pathology, (217)333-8414