DISEASES UNDER CONSERVATION TILLAGE SYSTEMS

The primary focus of this paper is on the effects of tillage and resid ue management on some diseases of cereal and oilseed crops in western Canada. In this region, reduced tillage lowers the impact of some root diseases but increases the impact of foliar diseases on cereals. Publ ished data showing evidence of the effect of reduced tillage on diseas es of oilseed crops is scarce. Diseases that were less economically im portant under higher tillage regimes may become more important with re duced tillage, but location and local environment largely influence wh ich diseases will be present. Crop rotation is a key factor in residue management for disease control. Disease and yield loss were higher wi th monoculture than with more diverse rotations. Some crops may pose a greater risk to succeeding susceptible crops that share common diseas e problems, such as Sclerotinia on peas and canola. A well-balanced ro tation should be at least 4 yr long with 50% of the interval devoted t o cereals and the remainder divided among pulses, flax, other oilseed crops, or forages. The risk of most diseases may be lowered by underst anding and managing the interactions between pathogens and crop residu e through modifying local environmental conditions, crop rotation, lim ited tillage, and antagonistic mycoflora. Single disease control measu res may be inadequate with reduced tillage; a holistic approach to cro p systems and plant health management may provide the solution to dise ase problems.