Hi - I am trying to find out the cause of multiple white powdery-looking spots on the leaves of our King Crimson maple tree. Others in the neighborhood have them as well, though the trees otherwise look healthy. what are the white spots, and are they damaging to the tree? if so, how can they be eliminated?

Hello Marion!

The symptoms you described appear to be the common fungal disease known as powdery mildew. Crimson King Norway Maple is unfortunately very susceptible to powdery mildew. Although unsightly, powdery mildew is relatively benign to the health and vigor of your tree since most infections occur late during the growing season. Therefore, treatment is often unnecessary.

However, there are several cultural practices that you can implement to help minimize future infection: (1) maximize airflow and direct sunlight to your tree (2) minimize humid conditions around your tree (3) rake and dispose of fallen leaves during autumn to remove the fungal spores (4) as necessary, increase the vigor of your tree by proper watering, fertilizing, and pruning.

Thank you for your question!