Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/3/2005
Publication Date: 3/20/2006
Citation: Schillinger, W.C., Paulitz, T.C. 2006. Reduction of rhizoctonia bare patch of wheat with barley rotations.. Plant Disease. 90:302-306 Interpretive Summary: Until now, rotation crops have not been shown to have any effect on Rhizoctonia bare patch, because of the wide host range of the pathogen, Rhizoctonia solani AG-8. However, after 6 years of continuous spring cereal production in a direct-seed experiment near Ritzville, we have observed that wheat following barley has less disease and greater yield than continuous wheat, even though barley is a host for this pathogen. The mechanisms behind this disease suppression are unknown.
Technical Abstract: The soil-borne fungus Rhizoctonia solani AG-8 is a major concern for farmers who practice direct seeding (i.e., no-till) in the inland Pacific Northwest, USA. Bare patches caused by rhizoctonia first appeared in 1999 during year 3 of a long-term direct-seed cropping systems experiment near Ritzville, Washington (290 mm annual precipitation). The extent and pattern of patches were mapped each year from 1999-2003 at the 8-ha study site with a backpack-mounted global positioning system equipped with mapping software. The average percentage area of bare patches ranged from 7.5% in 1999 to 11.7% in 2002. Comparison of patterns over years show that some patches increased in size, new patches formed, and some patches disappeared. Bare patches appeared each year in winter and spring wheat (Triticum aestivum L.), spring barley (Hordeum vulgare L.), yellow mustard (Brassica hirta), and safflower (Carthamus tinctorius L.). Crop rotation had no effect on the occurrence of bare patches caused by rhizoctonia during the first five years of the experiment, but continuous annual spring wheat had significantly greater area with bare patches compared to spring wheat following spring barley in a 2-yr rotation in 2002 and 2003. Research is underway or planned to determine why some bare patches disappear with time and on management practices to help alleviate the severity of the disease.