Sharpen your pruners to remove dead branches on woody ornamentals due to a two punch combination of drought and fungal pathogens such as Botryosphaeria and Seiridium. The long term effects of this summer’s drought are becoming visible in landscapes throughout the Southeast. Much of this dieback has appeared in the last month. Drought stress has predisposed many of our woody plants to infection by fungal pathogens and in some cases wood boring insects. Rhododendron and Leyland cypress are two common hosts for these diseases, but you may see similar dieback on laurel, viburnum, holly and some juniper species.
Chemical treatments are not effective for the control of most fungal canker diseases. The best preventive strategy is drip irrigation during dry periods. Once dieback has occurred, diseased branches should be pruned out below the canker; below discolored wood in the stems.
Taken from article written by Alan Windham, Ornamental Pest and Disease Update, 9/07
Photo of Seiridium canker on Leyland Cypress, credit to J. Williams-Woodward, UGA