Troubleshooting
Monterey Cypress problems — and how to fix them
Monterey Cypress (Cupressus macrocarpa) is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Seiridium canker
The most serious disease of Monterey Cypress. Seiridium cardinale causes resinous cankers, bark discolouration, and branch dieback ('flagging'). More severe in drought-stressed trees. Prune out infected branches promptly, sterilise tools, and improve tree vigour. No curative spray exists.
Cypress aphid (Cinara cupressivora)
Large brownish aphids feeding on inner branches cause yellowing, browning, and premature foliage drop, typically noticed in autumn. Treat with systemic insecticide or horticultural oil in spring when populations build. Remove dead inner foliage to improve air flow.
Wind root-rock
Fast growth in exposed, windy coastal sites produces tall trees vulnerable to wind throw if not properly anchored. Stake young trees with a low stake to allow stem flexing (building taper), remove the stake after 2 years, and avoid planting in shallow soils over rock.
Prevent monterey cypress problems before they start
Most monterey cypress issues are care-mismatch, not bad luck. Dial in the basics:
Monterey Cypress problems — FAQ
Why is my monterey cypress seiridium canker?
The most serious disease of Monterey Cypress. Seiridium cardinale causes resinous cankers, bark discolouration, and branch dieback ('flagging'). More severe in drought-stressed trees. Prune out infected branches promptly, sterilise tools, and improve tree vigour. No curative spray exists.
Why is my monterey cypress cypress aphid (cinara cupressivora)?
Large brownish aphids feeding on inner branches cause yellowing, browning, and premature foliage drop, typically noticed in autumn. Treat with systemic insecticide or horticultural oil in spring when populations build. Remove dead inner foliage to improve air flow.
Why is my monterey cypress wind root-rock?
Fast growth in exposed, windy coastal sites produces tall trees vulnerable to wind throw if not properly anchored. Stake young trees with a low stake to allow stem flexing (building taper), remove the stake after 2 years, and avoid planting in shallow soils over rock.