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 drylan d environment. General principles relating to factors influencing redu ced 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 histo ries are presented showing how reduced tillage may result in a decreas e in some diseases (common root rot) but in an increase in others (tan spot and septoria complex). For common root rot, inoculum levels of B ipolaris sorokiniana and isolation frequency are reduced under zero ti llage, although Fusarium species in the disease complex appear to be m ore prevalent. Differences in seeding depth and changes in soil temper ature and moisture appear to be the factors responsible for this patte rn. Zero tillage will not provide complete control of common root rot and should be used in conjunction with rotation using a diversity of c rop species to achieve maximum benefit. Foliar diseases increase under reduced tillage but not always to damaging levels. The biology and su rvival of the pathogens involved demonstrate why the residue is respon sible for the increase in disease. Crop rotation, resistant cultivars, and fungicides will reduce disease severity in reduced tillage system s and biological control agents may provide additional protection in f uture.