Borer Infestation in Yoshino Cherry Trees: Gel-Like Sap as a Warning Sign

A Yoshino cherry in a dry summer showed hard, resin-like gel spots on bark while other yard cherries remained healthy.

Diagnosis

The gel is a defense response to injury, typically from boring insects tunneling into the wood. Extensive tunneling causes gradual decline. The insects are already inside the tree, making control difficult with contact insecticides.

Management

Consult a local garden center for systemic insecticide options applied as trunk sprays or soil drenches. Preventive applications before insect entry are most effective. Maintain tree vigor with proper watering and fertilization to help it tolerate some borer activity.