Maple Bark Splitting: Sunscald Diagnosis and Borer Prevention

Three maples with severe bark splitting, foliage turning fall colors in mid-summer. Owner fears tree death.

Diagnosis: Sunscald

Winter injury: cells thaw on sunny days (south/west sides), rupture at night refreeze. Shows as sunken, discolored areas in spring. Fungi invade cracks. Young, thin-barked trees (maple, honey locust, linden, mountain ash) most susceptible. Heavy pruning exposes shaded bark to sun.

Prevention

• Wrap trunks with tree wrap paper each fall until bark roughens.
• Stage heavy pruning over years, not all at once.

Current Treatment

1. Spray splits with Merit (imidacloprid) to prevent borer entry.
2. Fertilize 10-10-10 at 1 lb per inch trunk diameter, watered in — boosts health to resist insects/fungi.