Red Maple Bark Decay and Yellow Leaves: Borer Treatment and Fertilization

2-year-old red maple near highway shows bark decay extending to base, yellow leaves with red veins (premature fall color). Owner fertilized with 12-12-12 and added cedar mulch.

Diagnosis: Borer Damage

Insect borers in woody tissue.

Treatment

1. Spray affected areas with Merit (imidacloprid) — kills insects in wounds, prevents new attacks.
2. Fertilize at correct rate: 1 lb 10-10-10 per inch trunk diameter, watered in. (Already fertilized this year; repeat next spring.)
3. Remove loose bark from wounds to speed healing.
4. Keep mulch (cedar is good) but not piled on trunk.