Hybrid Willow Black Canker: Act Fast or Remove the Tree

Black patches on stems, dying leaves, and rapid spread to the main trunk signal black canker (Glomerella miyabeana), a aggressive fungal disease of willows. Wet Ohio springs accelerate it.

Immediate Actions

• Prune out all blackened wood—cut well into healthy tissue.
• Destroy (burn or bag) infected debris; do not compost.
• Spray with Bordeaux mixture (copper sulfate + hydrated lime) at leaf-out next spring and repeat per label.

When to Remove

If >75% of the canopy is dead, the trunk is extensively blackened, or nearby healthy willows risk infection, remove the tree entirely. Scraping bark off does nothing—the fungus lives inside the wood. The fungicide Aliette (fosetyl-Al) may help but isn't a cure.

DIY Bordeaux Recipe

Dissolve 6.5 tsp copper sulfate in ~1 gal water. In a separate cup, mix 3 tbsp hydrated lime with water. Combine, add a squirt of dish soap as a spreader-sticker. Use same day; rinse sprayer thoroughly (add vinegar to neutralize corrosion).

Fixed copper fungicides are easier alternatives for spring applications.