Borer and Decay in Old Oak Trunk

Diagnosis

Spongy, barkless area with dark spots indicates borer damage with secondary decay fungi. Decay is slow; structural failure is years away if canopy remains healthy.

Management

• Spray affected trunk area with Onyx (bifenthrin) or Merit (imidacloprid) to kill borers.
• Fertilize with 10-10-10 at 1 lb per inch trunk diameter to boost vigor.
• Monitor for limb breakage; consult arborist if decay advances high into canopy.