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Reduction of Rhizoctonia Bare Patch in Wheat with Barley Rotations

Rhizoctonia bare patch caused by Rhizoctonia solani AG-8 is a major fungal root disease in no-till cropping systems. In an 8-year experiment comparing various dryland no-till cropping systems near Ritzville, WA, Rhizoctonia bare patch first appeared in year 3 and continued unabated through year 8. Crop rotation had no effect on bare patch during the first 5 years. However, from years 6 to 8, both soft white and hard white classes of spring wheat (Triticum aestivum L.) grown in a 2-year rotation with spring barley (Hordeum vulgare L.) had an average of only 7% of total land area with bare patches compared with 15% in continuous annual soft white wheat or hard white wheat (i.e., monoculture wheat). In years 6 to 8, average grain yield of both soft white wheat and hard white wheat were greater (P < 0.001) when grown in rotation with barley than in monoculture. Although both classes of wheat had less bare patch area and greater grain yield when grown in rotation with barley, monoculture hard white wheat was more severely affected by Rhizoctonia than soft white wheat. Soil water levels were higher in bare patches, indicating that roots of healthy cereals did not grow into or underneath bare patch areas. This is the first documentation of suppression of Rhizoctonia bare patch disease in low-disturbance no-till systems with rotation of cereal crops.