Diagnosing One-Sided Dieback in a Red Maple

Symptoms and Misdiagnosis

Left half of a red maple (facing sun) has brown leaves/seeds that don't fall, resembling fire blight. Owner had fire blight on pear previously.

Why It's Not Fire Blight

Fire blight does not attack maples. One-sided dieback points to other causes.

Three Probable Causes

1. Phytotoxicity: If it's a Japanese red maple recently sprayed with insecticide, chemical burn can kill one side.
2. Verticillium Wilt: Vascular fungus causing sporadic branch dieback, often one-sided initially.
3. Girdling Root: Root circling the trunk chokes off one side gradually over years, not suddenly.

Next Steps

Confirm species and spray history. If Verticillium is suspected, consult an arborist for soil testing and management. Girdling roots require root collar excavation.