Monday, 20 June 2005 - 1:40 PM
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Effect of Increased Diversity of Non-Grain Crops on Soil and Residue-Borne Diseases of Wheat in North Dakota.

Robert W. Stack and Marcia P. McMullen. North Dakota State University, Plant Pathology Dept, Box 5012, North Dakota State University, Fargo, ND 58105-5012

Diversity of row crops has increased significantly in ND in the past decade. Although sunflower production has stayed level, a decline in small grain production has been balanced by increases in canola, soybean, dry bean, field pea, lentil, and flaxseed. The current trend is for further increases in these and other non-cereal crops. A number of important wheat diseases are carried in residue or in the soil and recropping often favors them. A diversity of row crops available to farmers should favor rotation, which in turn should benefit wheat crops by reducing disease potential. Some diseases, such as the rusts of wheat, are windborne and little affected by rotation, but several important wheat foliar diseases and root rots are favored by recropping. Wheat foliar diseases such as tan spot overwinter on residue. Wheat soilborne diseases such as common root rot and Fusarium crown rot build up in soil after successive wheat crops. In ND studies on root rot at Langdon, ND and Williston, ND, we found that recropping to wheat favored root rot while rotation to some non-creal crops lessened it. These results agree with many other studies that have reported similar findings. In wheat foliar disease surveys, occurrence of tan spot was significantly greater in recrop than where a crop other than small grain preceeded wheat. In the past, lack of opportunity for crop rotation was cited by farmers as a reason for recropping to wheat. Availability of additional broadleaf crop choices suitable for planting in spring wheat areas should help to encourage disease-reducing crop rotations.

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