Leyland Cypress Browning: Canker Diseases and Management

19-year-old Leyland cypresses: inner needles browning, progressing outward. Tops still green.

Two Canker Diseases

1. Seiridium Canker (Most Destructive)

• Yellowing/browning on top/lateral branches (often spring).
• Thin, elongated cankers on stems/branches, sunken with raised margins, dark brown-purple.
• Cracked bark with resin flow. Cambium reddish-brown under ooze.
• Spreads until large portion destroyed.

2. Botryosphaeria (Bot) Canker

• Bright rust-colored branches, yellowing/browning shoots.
• Sunken, girdling cankers at base of dead shoots. Main trunk cankers up to 1+ ft.
• Little/no resin. Canker surface cracked, darker.
• Attacks stressed/wounded plants (freeze, drought, heat).

Management (Both Diseases)

1. Prune out brown/dead branches — improves appearance, reduces fungal inoculum.
2. Irrigate thoroughly every 7-14 days in drought (base of tree). Mulch beyond lowest limbs.
3. Sanitation: Destroy pruned material. Disinfect tools (alcohol or 1:9 bleach).
4. Remove extensively damaged or main-trunk-infected trees.
5. No fungicides effective once infected — prevention via stress reduction only.

Infection occurred years ago; symptoms now visible. Focus on water management and sanitation.