Differentiating Symptoms Of Soilborne Diseases From Winter Injury In Wheat

• Cephalosporium stripe. Infected leaves may initially show mosaic-like yellowing, which will be followed by the appearance of chlorotic longitudinal stripe on many leaves during jointing and heading. The yellow stripe will become prominent, running from the leaf blade to the sheath (Figure 2) and the veins are often darkened.

Figure 2 Cephalosporium stripe on the upper side of a leaf. 

Figure 3. Common root rot showing discoloration on the subcrown internodes and rotting of the crown.

• Common root and foot rots. Dark brown to black lesions on roots, sub-crown internodes, and stem bases. Lesions may merge, forming large areas of dead tissue in the crown. Discoloration of the sub-crown internode (Figure 3) is diagnostic for common root rot. Primary or secondary roots may appear brown or blackened.

Figure 4. Yellowing caused by Fusarium foot rot.

• Fusarium root, crown, and foot rots. Scattered patches of chlorotic (Figure 4), dead and dying plants may be seen in affected wheat fields. A diagnostic symptom of Fusarium foot rot is a cottony pink mycelium that may appear on affected stem bases. Dark brown lesions around the node of mature plants and the whole stem base may become girdled by a dark brown lesion.

• Pythium root rot. Symptoms are likely to be more uniformly distributed in the field than symptoms of other soilborne diseases, but are also subtle and may not be easily noticed. Symptoms could include stunting, yellowing, and missing plants and those that may look nitrogen-deficient, have poor tillers, and poorly filled heads.

Figure 5. Plants showing symptoms of take-all (white heads). 

• Rhizoctonia root rot. Patches of stunted or missing/dead (bare patch) plants should not be confused with winter killed areas. When you dig up the plants, root ends could appear reddish brown and taper to a fine point, which is a diagnostic symptom of this disease. Also, the root could appear constricted or pinched. In fields where infections might have occurred before winter injury, it is not likely that plants can outgrow the disease.

• Take-all. Symptoms include stunting, plants with few tillers, and chlorosis. Other symptoms will become obvious near heading as plants can die prematurely and have white heads from distinct bleaching (Figure 5). Premature heads may contain shriveled grain and become darkened from secondary infection. Affected plants will pull up easily or break near the soil line and the roots will appear sparse, blackened, and brittle.