Seedling blight, spot blotch, and common root rot in Quebec and their effect on grain yield in barley.
When barley fields in SW Que. were surveyed the estimated intensities of seedling blight, spot blotch on flag and penultimate leaves, and common root rot in 1977 were 24.9, 8.8, 14.8 and 69.7%, respectively, and 17, 0.5, 1.6 and 38.7%, respectively, in 1978. The estimated grain losses relative to the yield of plants in common root rot class 0-10% were 38.9% in 1977 and 33% in 1978. An increase in common root rot severity resulted primarily in a reduction of ears/plant and seeds/ears, which contributed to grain yield loss. Highly significant correlations occurred in both years between seedling blight intensity and common root rot intensity, seedling blight intensity and yield loss, and common root rot intensity and yield loss. There was variation in correlations between spot blotch intensity and other diseases; spot blotch intensity was not significantly correlated with yield loss. The predominant organisms isolated from diseased subcrown internodes of barley were Cochliobolus sativus and Fusarium spp. (54 and 63.1%).