Water Oak Borer Damage: Insecticide Treatment and Tree Health

Identifying Borer Activity

Two black holes (~1 inch wide) penetrating deep into a water oak trunk with sap leakage indicate borer insect infestation. These beetles bore through bark and wood, triggering sap flow from wounds.

Systemic Insecticide Treatment

Apply Merit (imidacloprid) insecticide to the bark area. As a systemic, it's absorbed into bark and wood, killing borers inside. The tree can then heal over wounds. Available at local nurseries.

Addressing Underlying Stress

Borers typically attack stressed trees. Fertilize with 10-10-10 at 1 pound per inch of trunk diameter, scattered around the tree and watered in thoroughly. This boosts tree vigor and recovery capacity.

Monitoring and Prevention

• Watch for new holes or sap flow
• Maintain consistent watering during drought
• Avoid mechanical trunk damage
• Consider preventive Merit applications for valuable trees

Early intervention with systemic treatment combined with improved tree nutrition gives the best chance for recovery.