Italian Cypress Canker: Seiridium, No Cure, Manage Stress

Black Oozing Lesions on Italian Cypress = Seiridium Canker

Your 9 ten-year-old cypresses near the coast have black, oozing cankers. This is Seiridium canker (Seiridium unicorne), the most damaging cypress disease. Stress (weather, wounding) triggers it. Resin flow alone isn’t diagnostic—healthy cypress also bleed resin.

No Chemical Cure

• Prune infected branches 1 inch below canker; sterilize tools between cuts (alcohol or 10% bleach).
• Destroy severely affected plants.
• Avoid water stress and wounding.
• Phosphoric acid injections are not proven effective.

See Arizona guide for details.