Agronomic practices and common root rot in spring wheat: Effect of tillage on disease and inoculum density of Cochliobolus sativus in soil

The effect of tillage, primarily zero tillage, on common root rot in spring wheat was studied at three locations in Saskatchewan. Generally, disease intensity was lower under zero than conventional tillage. It was significantly lower in 6 of 10 years at Scott and in 3 of 7 years at Swift Current. Differences occurred in wheat in oilseed - wheat - wheat, fallow - oilseed - wheat, and fallow - wheat rotations and in continuous wheat. On average, the disease intensity in minimum tillage plots at Swift Current was intermediate between that in zero and in conventional tillage. Effect of depth of seeding usually was significantly greater under conventional than zero tillage. Covariance analysis indicated that seeding depth influenced the disease intensity: shallow seeding was associated with the reduced disease under zero tillage. Isolations from subcrown internodes showed Cochliobolus sativus to be the dominant cause of common root rot at the three locations, with a positive association between the frequency o...