Your maple may be infected with powdery mildew disease. Here are some strategies to minimize the problem. Hope this helps for next year.
Anthracnose, leafspots, and powdery mildews can be curbed by using a multifaceted approach. These diseases are often effectively controlled by following good sanitary and cultural practices and are rarely serious enough to warrant chemical control.
Since many of these fungi overwinter on fallen leaves, it is important to rake and remove fallen leaves from the vicinity of the tree in autumn. This reduces the number of spores available to infect emerging leaves in spring or during the following growing season.
Tree vigor should also be maintained by proper watering, composting over the root area, and proper pruning.
During the summer, trees in the Northeast frequently experience drought. A good, deep watering in the daylight hours once a week will help the vigor of the tree, reducing stress. Water deeply and slowly.
For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service