Didymascella thujina

Didymascella is commonly known as Cedar leaf blight.

Description:  It is a brownish blotching on cedar leaves.  It kills the cedar’s leaf scales and this reduces the photosynthetic area of the tree, and this is especially bad for seedlings and saplings.

Identification:  The blotching caused by cedar leaf blight can be easily confused with the color changes that occur in the fall.  To tell the difference you can look for brown or black spots on the leaf scales.  These are the fruiting bodies of the fungus.

Hosts:  Western redcedar.

Distribution: Throughout the range of western redcedar.

Sources:  Field Guide to the Common Diseases and Insect Pests of Oregon and Washington Conifers.