Flowering Cherry Bacterial Canker: Gumming, Dieback, and Copper Spray

Symptoms

Cherry blossom tree: yellowish, slimy, irregular "blob" near base of trunk (like Jell-O).

Diagnosis: Bacterial Canker

• Caused by Pseudomonas syringae.
• AKA: bacterial blast, bacterial gummosis.
• Prime attacker of cherry (especially young).
• Cool, moist conditions favor.

Disease Progression

1. Leaf yellow/green discoloration → premature drop.
2. Bark lesions ooze amber/yellow gum (spring, fall, winter).
3. Blossoms wilt/die in cool wet springs.
4. Limbs weaken, die; severe defoliation.
5. Fruit: sunken lesions. Leaves: angular holes.

Management (Difficult)

• Pruning: Remove cankered branches. Sterilize shears with alcohol between EVERY cut.
• Sanitation: Destroy all debris.
• Fall Copper Spray: Basic copper fungicide prevents new infections.
• Avoid Spring Pruning: Wet weather spreads bacteria.

Key Challenge

Pruning wounds = entry points. Sterilization discipline is critical but often neglected. No chemical cure for established infections.