Black Spots on Japanese Maple Bark: Likely Harmless Lichens

Japanese green maple has black spots on bark. Owner worries about disease.

Assessment

Without a photo, likely lichens—common, harmless, indicate clean air. If tree is otherwise healthy, no concern.

Check For

• Oozing liquid from spots (could be insect borers).
• Cankers or sunken areas.

Send photo if unsure.