Cedar needle blight
Damage, symptoms and biology
Young seedlings and saplings sustain the most damage where stem or branch death may occur. Disease on trees older than 4 to 5 years can retard growth. Disease levels are highest in dense stands where humidity levels are high. Such conditions can occur in forest nurseries where the disease can be a serious problem.
The symptoms appear as small whitish spots on the upper leaf surface in the spring, initially on one-year-old foliage. They turn brown and cover the entire needle. Apothecia become visible in late June. They are brownish red and turn black at maturity. The ascospores are released from June to October and travel several kilometres, with no loss of viability. They overwinter on green foliage and cause infections the following season.
Cedar leaf blight (also known as Keithia blight) can be confused with normal foliage colour changes that occur on western red cedar in the autumn. However, seasonal colour changes affect the entire plant in contrast to the scattered symptoms of the disease.