Four barley (Hordeum vulgare L.) cultivars, Heartland, Harrington, Johnston and Kasota, were compared at the seedling stage for disease reactions to net blotch, caused by Pyrenophora teres f. teres, and spot blotch, caused by P. teres f. maculata. The plants were inoculated once with serial concentrations of conidia and then misted. Two misting treatments were tested, 24 and 48 h. The linear relationship between inoculum density and diseased leaf area was used to estimate the inoculum dosage causing 50% diseased area (ED₅₀) for Leaf 2 from the plant base and that causing 15% diseased area (ED₁₅) for Leaf 3, and to compare resistance across cultivars. The linear relationship for diseased leaf area over time was used to estimate the infection rate and to compare resistances. The ED₅₀ and ED₁₅ values adequately differentiated moderate resistance from susceptibility among the four cultivars. The lack of a linear relationship over time for diseased area of Leaf 3, caused by P. teres f. teres for cvs. Heartland and Kasota indicated the more resistant nature of Leaf 3 versus Leaf 2 in the two cultivars.

Heartland was the most resistant in terms of higher ED₅₀ and ED₁₅ values, having a lower infection rate. Kasota had intermediate resistance. Harrington and Johnston were susceptible. Comparisons of the two pathogens on these two cultivars showed that P. teres f. maculata, with higher ED₅₀ and ED₁₅ values, was significantly less virulent than P. teres f. teres. A mist period of 48 h tended to obscure the differences between resistant and susceptible cultivars, as compared to 24 h.

Results suggest that ED₅₀ and ED₁₅ values can be used as criteria for screening seedling resistance, and that 24 h of misting is better than 48.