Cause Two fungi, Rhizoctonia solani and R. oryzae, that survive in soil and crop residues. Various factors favor this disease including heavy straw residues on or near the soil surface during fallow years; no-till cropping systems; and annual cropping of small grains.
Symptoms Stunted plants often are within rows of plants that look normal. Stunted plants also may be in distinct patches. Maturity is delayed in stunted plants. Roots rot and become severed in the top 4 inches. Symptoms on seedlings usually include a dark brown root terminus that tapers to a fine point 2 to 3 inches from the crown or seed, representing the upper half of the lesion that severed the root. Plants whose crown roots are all rotted are anchored only by the subcrown internode, and they may either fall over or "blow" out of the soil as late as after heading. Severe disease may occur where soils have high concentrations of these pathogens; seedlings can die out in large patches across a field.
Cultural control
- Disturb the soil with a rod-weeder or cultivator several days or more before seeding.
- If a preplant tillage is not planned, delay planting at least 21 days after applying a broad-spectrum herbicide to kill weeds and volunteer plants. This is especially important for spring-seeded barley.
- Rotations to fallow help reduce the severity of disease.
Chemical control No effective chemical treatment is known.
Biological control
- Bexfond at 7 to 14 fl oz/A. O