Managing Borer Damage and Decay in a Mature Oak: Treatment and Fertilization

Dual Threat

Wood borers create entry for decay fungi. The fungi rot the heartwood slowly, weakening limbs over decades.

Action Plan

1. Spray Merit into borer holes.
2. Fill hollow cavity with expanding foam to exclude water.
3. Fertilize with 10-10-10 at 1 lb per inch of trunk diameter (circumference ÷ 3.14). Apply on your property proportionally to dripline area.
4. Repeat fertilization spring and fall.

Long-Term

Healthy outer growth compensates for internal decay. Monitor for large limb failure in storms.