Fire Blight on Knock Out Rose: Identification and Control

Sudden Cane Dieback on Mature Knock Out

One of two 4-year-old Knock Outs in same bed suddenly lost 1/3 of canes—brown, scorched leaves like blowtorch damage. Excessive May rain; other roses fine. Pruned affected canes.

Diagnosis: Fire Blight

Bacterial disease (Erwinia amylovora), rare in roses but possible. Causes scorched, blackened canes.

Management

• Prune 6+ inches below visible damage.
• Sterilize tools between cuts (1:8 bleach:water or alcohol).
• Apply copper spray late fall/early spring to all roses in area.
• Avoid high-nitrogen fertilizer and heavy pruning—both promote susceptible succulent growth.

Monitor closely; fire blight spreads in wet conditions.