Managing cereal diseases under reduced tillage

This paper examines the effects of reduced tillage on cereal diseases commonly found in the Canadian prairies and relates mainly to a dryland environment. General principles relating to factors influencing reduced tillage and reducing the risk of disease loss are illustrated with examples. Disease problems vary with environment and comparisons are made between the prairies and other locations. Two detailed case histories are presented showing how reduced tillage may result in a decrease in some diseases (common root rot) but in an increase in others (tan spot and septoria complex). For common root rot, inoculum levels of Bipolaris sorokiniana and isolation frequency are reduced under zero tillage, although Fusarium species in the disease complex appear to be more prevalent. Differences in seeding depth and changes in soil temperature and moisture appear to be the factors responsible for this pattern. Zero tillage will not provide complete control of common root rot and should be used in conjunction with rotation using a diversity of crop species to achieve maximum benefit. Foliar diseases increase under reduced tillage but not always to damaging levels. The biology and survival of the pathogens involved demonstrate why the residue is responsible for the increase in disease. Crop rotation, resistant cultivars, and fungicides will reduce disease severity in reduced tillage systems and biological control agents may provide additional protection in future.