Oak Trunk Decay: Management and Structural Support

Decay Fungi vs. Living Tissue

The hollowed areas in your Florida oaks are caused by wood‑decay fungi entering through old wounds (possibly borer holes). Crucially, these fungi digest only dead heartwood—they do not kill living cambium.

What You Can Do

• Remove loose bark around the cavity to help the tree form woundwood (callus).
• Do not fill cavities—concrete or foam traps moisture and accelerates decay.
• Treat for borers: Spray trunk with a systemic insecticide containing imidacloprid (Merit) to prevent new borer entry.
• Fertilize: 1 lb 10‑10‑10 per inch of trunk diameter, scattered and watered in. Repeat in fall.

Structural Concern: Co‑Dominant Stems

The decay weakens the union where two large trunks meet. Install a cable‑brace system (through‑bolts with synthetic cable) to reduce wind‑splitting risk. See Texas A&M guide on cabling.

Hurricane Resilience

Decay alone won’t fell the tree, but combined with a weak union and high winds, failure risk rises. Cabling + vigor improvement = best insurance.