Tillage affects the level of disease by reducing the population of wheat pathogens surviving from one year to the next. Plowing, disking, or chiseling fields soon after wheat harvest incorporates the residue into the soil. Soil bacteria begin to utilize the food reserves in the wheat residues and compete with the pathogens for this important food base. Most pathogens cannot compete effectively with soil bacteria and usually die within a few months of tilling the soil. Tillage achieves the same effect as rotation, but requires much less time.
The planting of no-till wheat, while an effective soil conservation practice, has increased the level of important and destructive diseases. Take-all, powdery mildew, tan spot, and the Stagono-spora diseases are generally more severe in no-till because the fungi that cause these diseases survive from one year to the next on residues on the soil surface and are ready to infect the young plants soon after germination. These disease problems are enhanced when wheat is in continuous production under no-tillage systems.
Producers using no-till or other conservation tillage systems must rely on other disease-management methods. Crop rotation is of primary importance in these systems with at least two- to three-year rotation away from wheat. Other methods that help to limit yield losses from disease are the use of resistant varieties, delayed planting date, seed treatments, and foliar fungicides.