Cedar leaf blight
Last updated on January 30, 2025Didymascella thujina
Cedar leaf blight affects western redcedar across its range in British Columbia and is caused by the pathogen Didymascella thujina. The blight is most damaging in the south and west coast regions.
On this page
Description
Signs of cedar leaf blight can appear as early as the fall on the current year’s growth. However, in most cases, the disease does not show show until one year after infection. Infection occurs when spores are released from fruiting bodies on previously infected leaflets.
High humidity, dew, or spring rainfall are important for both spore release and spore germination. Once spore release has completed, the fruiting bodies fall from the leaflet leaving a shot hole appearance to the leaflet.
Host tree species
Cedar leaf blight affects only western redcedar.
Damage symptoms
Symptoms include dead individual leaflets with a tan to brown colour and oval-shaped fruiting bodies. Cedar leaf blight infection reduces a leaflets photosynthetic capacity and, if infections are severe, the growth of the tree will be impacted by stress to the host.
Management
Cedar leaf blight can be controlled in forest seedling nurseries through cultural or chemical control methods. Employing these methods will ensure that disease-free seedlings are planted in reforestation sites. However, once the seedlings are in the site they will becomes infected by the disease present in surrounding cedar forests. There is no known information on protecting trees from cedar leaf blight in forested stands.
Identification images
Cedar leaf blight on western red cedar. Brown coloured dead leaflets with black fruiting bodies.
Further reading
Read about cedar leaf blight in the Field Guide to Forest Damage in B.C. (PDF, 6.6MB)
Contact information
Contact us if you have questions about cedar leaf blight in British Columbia.