Dealing with Borer Damage in Crimson Maple Trees

A homeowner noticed two limbs on their crimson maple tree had split and were leaking sap down the trunk. The tree was transplanted 4.5 years ago at 30 feet tall and appeared healthy otherwise. This scenario typically indicates an infestation by borers—insects that bore into the trunk, causing the tree to exude sap as a defense response.

Identifying the Problem

Borers target stressed or wounded trees. The sap leakage is the tree's attempt to flush out the invaders. Left untreated, borers can weaken the tree structurally and lead to further decline.

Recommended Treatment

Apply an insecticide containing imidacloprid (such as Merit) directly to the wound. This systemic treatment kills borers inside the trunk, allowing the tree to stop exuding sap and heal naturally. Consult your local nursery for Merit or equivalent products.

Prevention Tips

• Keep the tree well-watered during dry periods.
• Avoid mechanical damage to the trunk.
• Monitor for early signs of borer activity, such as sawdust-like frass or additional sap flow.