Leyland Cypress Turning Brown: Canker Diseases and Management

Why Are My Leyland Cypress Trees Browning in Patches?

A homeowner lost one Leyland cypress last fall; now another shows patchy browning in spring. The rest appear healthy.

Likely Culprits: Seiridium & Botryosphaeria Cankers

These fungal diseases are increasingly common on Leyland cypress. Symptoms:

• Sunken, dark brown/purplish cankers on bark, often with resin flow (Seiridium).
• Bright reddish-brown dead twigs/branches contrasting with green foliage.
• Small black fruiting bodies on cankers.
• Botryosphaeria cankers may be longer, with less resin, and can girdle branches.

Management (No Chemical Cure)

• Prune out infected branches 1 inch below the canker; destroy debris.
• Sterilize tools between cuts (70% alcohol or 10% bleach).
• Reduce stress: mulch annually, water during drought, avoid heavy fertilization and severe pruning.
• Remove severely affected trees.

Prevention

Plant in well-drained soil, provide adequate spacing for air flow, and avoid overhead irrigation.