ARS | Publication request: Effects of Shading on Cerospora Leaf Spot in Bigleaf Hydrangea

Submitted to: Southern Nursery Association Research Conference
Publication Type: Proceedings
Publication Acceptance Date: August 20, 2008
Publication Date: December 1, 2008
Citation: Li, Y., Windham, M.T., Trigiano, R.N., Reed, S.M., Spiers, J.M., Rinehart, T.A. 2008. Effects of Shading on Cerospora Leaf Spot in Bigleaf Hydrangea. Southern Nursery Association Research Conference, vol. 53 pp. 379-380 .

Interpretive Summary: Cercospora leaf spot is a common disease of bigleaf hydrangea in ornamental nurseries and gardens in late summer and fall. Some degree of shade is favorable to growth of bigleaf hydrangeas although they are grow normally in full sun. Effects of light on development of diseases caused by Cercospora species in coffee, sugar beet and banana have been studied, but effects of shading on leaf spot of hydrangea are unclear. In order to develop screening methods for disease resistance and integrated disease management, effects of shading densities on disease development of Cercospora leaf spot were investigated in six bigleaf hydrangea cultivars.

Technical Abstract: Shading densities significantly affected disease severities of Cercospora leaf spot on bigleaf hydrangeas. In general, lower disease severities were associated with higher shading densities. However, significantly differences in disease severities among cultivars could not be detected in higher shading densities with 90% and 60% shade. These results suggest that planting bigleaf hydrangeas under shade could be an effective component in integrated management of the disease. Screening of bigleaf cultivars for leaf spot resistance needs to be conducted under full-sun or low shading density to avoid false conclusions.