Insights into the prevalence and management of soilborne cereal pathogens under direct seeding in the Pacific Northwest, U.S.A.

Abstract

Direct seeding or no-till leaves the soil undisturbed, except where the seed is planted and the soil fertilized. It offers several advantages in small-grain cereal production, including reduction in labor and other operating costs, reduction of soil erosion, and improvement of soil quality. However, only about 10% of small grains in the U.S.A., and 6% of the small grains in the Pacific Northwest region of the U.S.A. are currently direct seeded. Root diseases are major constraints to adoption of direct seeding; they increase because of lack of tillage, increased crop residue left on the surface, and typically cooler and wetter soil conditions in the spring. This review covers some recent research on the four most important root diseases of cereals in the Pacific Northwest and their causal agents. These diseases are rhizoctonia root rot and bare patch [Rhizoctonia solani AG-8, Rhizoctonia oryzae], pythium damping-off and root rot [Pythium spp.], take-all [Gaeumannomyces tritici var. tritici], and fusarium foot rot [Fusarium pseudograminearum and Fusarium culmorum] We discuss how these diseases are affected by direct seeding and the impact of management strategies, including crop rotation, residue management, control of inoculum from volunteers and weeds, fertilizer placement, genetic tolerance, biological control, development of natural suppressiveness, and prediction of risk through DNA-based detection methods.Key words: soilborne pathogens, cereal, direct seeding, management strategies, no-till.