Tuesday, 8 November 2005
5

Reduction of Rhizoctonia Bare Patch Disease in Wheat with Barley Rotations.

William F. Schillinger, Washington State University, Dryland Research Station, P.O. Box B, Lind, WA 99341 and Timothy C. Paulitz, USDA-ARS, Root Disease and Biological Control Unit, Pullman, WA 99164-6430.

Rhizoctonia bare patch caused by Rhizoctonia solani AG-8 is a major fungal root disease in no-till cropping systems. In an 8-year dryland no-till cropping systems experiment near Ritzville, Washington, USA, 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. But from years 6 to 8, both soft white (SW) and hard white (HW) classes of spring wheat (Triticum aestivum L.) grown in a 2-year rotation with spring barley (SB) (Hordeum valgare L.) had an average of only 6.6% of total land area with bare patches compared to 15% in continuous annual SW or HW (i.e., monoculture wheat). Monoculture HW in patches was damaged or killed by Rhizoctonia before seedling emergence as evidenced by a 40% reduction in plant stand compared to monoculture SW and HW or SW in rotation with SB. In years 6 to 8, average grain yield of both SW and HW were greater (P<0.001) when grown in rotation with SB than in monoculture. Although both classes of wheat had less bare patch area and greater grain yield when grown in rotation with SB, monoculture HW was more severely affected by Rhizoctonia than SW. Soil water levels were higher in bare patches, indicating that roots of healthy cereals do not grow into/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.

Handout (.pdf format, 145.0 kb)

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