Effect of Inoculations with Cochliobolus sativus at Specific Growth Stages on Grain Yield and Quality of Malting Barley1

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Field experiments were conducted to characterize the relationship between severity of spot blotch epidemics in barley (Hordeum vulgare L.) and loss in grain yield and malt quality. The effect of spot blotch on yield and quality must be known to evaluate the economic benefit of specific disease control strategies such as the use of resistant cultivars or fungicide. Spot blotch epidemics of different intensities were established by inoculating field plots at specific barley growth stages and by using two cultivars, ‘Larker’ and ‘Dickson’, that differ in disease reaction to spot blotch. Inoculations with Cochliobolus sativus reduced yield, yield components, and malt quality of Larker more than Dickson. Yield and quality factors were more adversely affected if inoculation was just prior to flag leaf emergence or at anthesis than at early milk development. Reduction in yield in response to spot blotch epidemics was largely a function of reduction in kernel weight. In 1983, field plots of Larker, Dickson, ‘Glenn’, ‘Bumper’, ‘Robust’, and ‘Hazen’ were either inoculated with C. sativus spores or sprayed with fungicide to evaluate changes in cultivar resistance to spot blotch since the release of Larker in 1961. Based on percentage yield loss [(yield of inoculated plots)/(yield of fungicide‐treated plots)], a significant improvement in disease resistance was achieved with the release of Dickson in 1964. Percentage yield losses observed for Dickson (released in 1964), Glenn (released in 1978), Bumper (released in 1980), and Robust (released in 1983) were not statistically different from each other, indicating no further improvement in disease resistance over Dickson. However, a significant improvement in disease resistance was again achieved with the release of Hazen in 1984.