Troubleshooting
Showy mountain ash problems — and how to fix them
Showy mountain ash (Sorbus decora) 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.
Fire blight
Shoots wilt and blacken with a burnt appearance. Remove infected material well below the lesion with sterilised pruners; apply copper-based bactericide preventively during bloom.
Apple scab (Venturia inaequalis)
Dark, scabby lesions on leaves and fruit in wet springs. Rake and dispose of fallen leaves; consider a preventive fungicide programme from bud-break if historically problematic.
Cedar-apple rust (Gymnosporangium sp.)
Orange-yellow leaf spots appear where Eastern red-cedar (Juniperus virginiana) grows nearby. Avoid planting adjacent to Juniperus hosts; fungicide at bud-break if needed.
Prevent showy mountain ash problems before they start
Most showy mountain ash issues are care-mismatch, not bad luck. Dial in the basics:
Showy mountain ash problems — FAQ
Why is my showy mountain ash fire blight?
Shoots wilt and blacken with a burnt appearance. Remove infected material well below the lesion with sterilised pruners; apply copper-based bactericide preventively during bloom.
Why is my showy mountain ash apple scab (venturia inaequalis)?
Dark, scabby lesions on leaves and fruit in wet springs. Rake and dispose of fallen leaves; consider a preventive fungicide programme from bud-break if historically problematic.
Why is my showy mountain ash cedar-apple rust (gymnosporangium sp.)?
Orange-yellow leaf spots appear where Eastern red-cedar (Juniperus virginiana) grows nearby. Avoid planting adjacent to Juniperus hosts; fungicide at bud-break if needed.