Oak Borer Management: Vigor, Merit Spray, and Japanese Maple Safety

Case

30-yr-old oak (NW Arkansas) attacked by borers. Half tree healthy. Concern: will borers attack nearby Japanese maple?

Borers 101

• Attack stressed trees only (drought, injury, disease).
• Healthy, vigorous trees resist via sap pressure/defense compounds.
• Species-specific mostly—oak borers unlikely on maple.

Two-Pronged Treatment

1. Boost Vigor: 10-10-10 at 1 lb/inch trunk diameter. Scatter, water in.
2. Trunk Spray: Merit (imidacloprid) now + April. Kills larvae in trunk + adults laying eggs.

Japanese Maple Safety

Different borer species. Maple borers exist but attracted to stressed maples. Keep maple vigorous (water, mulch, no wounds) = best protection.

Monitoring

• Check for new exit holes, frass, canopy thinning.
• Arborist eval if decline continues.
• Consider soil test for targeted fertilization.