The incidence of Swiss needle cast on Douglas-fir has increased significantly in recent years on the Oregon coast. Genetic variation in symptoms of disease infection, as measur- ed by foliage traits, was assessed in two series of progeny trials

The incidence of Swiss needle cast on Douglas-fir has increased significantly in recent years on the Oregon coast. Genetic variation in symptoms of disease infection, as measured by foliage traits, was assessed in two series of progeny trials to determine whether these “crown health” indicators were under genetic control and correlated with tolerance; tolerance being continued growth in the presence of high disease pressure. Foliage traits generally had lower heritabilities than growth traits and were usually correlated with diameter growth. Foliage traits of crown density and color appeared to be reasonable indicators of disease tolerance. In the absence of basal-area data, assessing crown density and color can help screen for families that show tolerance to the disease.