Leyland Cypress Decline: Cankers, Pests, and Professional Diagnosis

Leyland Cypress Turning Brown: Multiple Possible Causes

Leyland cypresses in dense plantings are prone to three serious canker diseases and insect issues. Symptoms described (browning from bottom up, white sticky blobs) suggest:

Possible Diseases

• Seiridium canker: Bleeding cankers, needles fall easily.
• Botryosphaeria canker: Sunken V-shaped cankers, needles persist.
• Passalora needle blight: Browning starts low/inside, spreads up/out. No cankers.

White Sticky Blobs

Likely aphids or scale insects producing honeydew.

Action Required

DIY diagnosis is unreliable. Contact a professional:

• Andy Boone, retired forest pathologist: dendrodiagnostics@gmail.com
• Website: dendrodiagnostics.com
• Local certified arborist or state forestry extension.

Long-Term Note

Leyland cypress is disease-prone, especially outside its ideal range. Consider replacing with Green Giant arborvitae for a more durable screen.