Diagnosing Fire Blight and Powdery Mildew in 20-Year-Old Spirea

Two 20+ year spireas: one had back half die last year; now both have dead spots. Owner trimmed dead, now both look like bad haircuts. Cause and cure?

Primary Suspect: Fire Blight

• Bacterial disease spread by insects/rain.
• Destructive to spirea, pears, apples, hawthorns.
• Symptoms: declining leaves/limbs.

Treatment

1. Prune infected branches to healthy wood well below blight.
2. Spray streptomycin (or similar) to protect blossoms.
3. Avoid excess nitrogen (promotes blight).
4. Dispose of fallen infected leaves.
5. Multiple fungicide applications per label.

Secondary: Powdery Mildew

General garden fungicide works. Clean up fallen leaves to prevent re-infection.

Proximity to pome fruits increases fire blight risk.