The fungus that causes head scab in wheat and barley survives in the residues of previously infected crops. The fungal population is often the greatest in corn or wheat residue, and planting small grains directly into fields with large amounts residue from these crops remaining on the soil surface increases the risk of disease.
Rotation with broad leaf crops such as soybean, sunflower or canola is most likely to reduce the risk of disease. The length of rotation needed to reduce the risk of disease varies throughout the wheat and barley production regions of the US, and is affected by the rate of residue decomposition and subsequent decline of the fungal population. In areas where the rate of residue decomposition is high, a single year of rotation may be adequate to reduce the fungal population and lower the risk of disease. However, 3 or more years of rotation may be needed to reduce risk of disease in areas where cold temperatures or dry conditions slow the rate of decomposition of residue.