Leyland Cypress Browning: Canker Diseases and Management

Our Leyland cypress trees in south Louisiana turned brown last year, recovered this spring, but are now declining again on more trees. Some bare branches show small green buds.

Common Leyland Cypress Diseases

Leyland cypress (× Cupressocyparis leylandii) faces several fungal diseases:

Seiridium Canker

Caused by Seiridium unicorne, this is the most damaging disease. Sunken, dark brown or purplish cankers form on stems and branches with heavy resin flow. Affected twigs turn bright reddish-brown. Spores spread via water splash and pruning tools. No chemical controls exist. Prune infected branches 1 inch below cankers, sterilize tools between cuts (rubbing alcohol or 1:9 bleach solution), and destroy severely affected plants.

Botryosphaeria Canker

Similar symptoms but with less resin flow. Long, narrow trunk cankers may extend a foot or more. Occurs on stressed plants. Management includes mulching, adequate watering during drought, avoiding heavy fertilization and severe pruning. No effective chemical control.

Cercospora Needle Blight

Browning starts on lower interior needles, spreading upward. Tiny greenish pustules appear on needles. Control with copper fungicides (e.g., Kocide) at 10-day intervals from bud break until new growth matures.

Diagnosis Resource

Compare symptoms with photos at UGA Extension publication B1229.