Rose Canker Disease: Branch Dieback with Brown Healing

Identifying Alternaria Stem Canker

Rose branches falling off with brown, cleanly scabbed bases showing gradual girdling indicates Alternaria stem canker—a fungal disease forming concentric rings in the cankered area. This is not nitrogen deficiency from wood mulch.

Confirmation & Treatment

1. Inspect canker for concentric rings (target-like pattern).
2. Prune 4–6 inches below visible canker into healthy wood.
3. Disinfect pruners between cuts (10% bleach/alcohol).
4. Apply rose fungicide (local nursery can recommend specific products for Alternaria).
5. Improve air circulation; avoid overhead watering.

Mulch Clarification

Raw wood mulch temporarily ties up nitrogen, but urea application would have corrected this. The progressive, ringed canker is distinctly fungal—nutrient issues don't create this pattern.