Transplanted Leyland Cypress Browning: Canker Diseases and Management

Two 10-foot Leylands transplanted in fall now brown after surviving winter. Owner seeks diagnosis and remedy.

First: Verify Viability

Scrape bark on twigs—green cambium = alive. Limber twigs = alive. Brittle/brown = dead.

Primary Suspects: Canker Diseases

Seiridium canker (Seiridium unicorne):

• Yellow/brown foliage on top/lateral branches
• Sunken, dark cankers with resin flow
• Black fruiting bodies (pinhead-sized)
• Spread by water splash, tools

Botryosphaeria (Bot) canker (B. dothidea):

• Similar foliar symptoms
• Sunken cankers, little/no resin
• Long trunk cankers possible
• Stress-triggered (drought, freeze, heat, wounds)

Management (No Cure, Only Suppression)

• Prune dead branches 1″ below canker; sterilize tools (alcohol/bleach) between cuts.
• Destroy pruned material.
• Mulch beyond dripline; irrigate 7–14 days during drought.
• No effective fungicides once infected.
• Remove severely affected trees (main trunk cankers).

Root Cause

Transplant stress + possible root damage during move predisposed trees. Infection occurred months before symptoms appeared.