Linden Borers and Decay: Treat Borers, Accept Hollows

Mature lindens have borers deep in trunk, bark peeling in crotches, 5″ branches may break. Malathion won’t work.

Borers

• Use permethrin (Onyx) or imidacloprid (Merit) trunk spray—penetrates bark.
• Or soil-applied imidacloprid (Bayer Advanced) for systemic uptake.

Decay/Hollows

• Peeling bark, brown interior = heartwood decay (fungi).
• Living cambium under bark is separate; tree can live decades hollow.
• Hollow limbs may break—prune if over targets.

Vigor

• Fertilize: 10-10-10 at 1 lb/inch trunk diameter, scattered, watered in (before rain).
• Healthy tree resists borers and walls off decay.

Bottom Line

Spray Onyx/Merit or drench imidacloprid for borers. Fertilize. Accept hollows as natural; prune hazardous limbs only.