A Technical Report from The Bartlett Tree Research Laboratories
Keithia blight, a disease caused by the fungus Didymascella, leads to blighting, twig dieback, and branch death on species of Thuja and Juniperus. The pathogen is most damaging on western red cedar, Thuja plicata. This disease is found throughout North America but is most common in the Pacific Northwest and Western Canada. Small trees, lower branches of larger trees, and hedges are most likely to be affected.