This is a common disease on maples, but is not serious and does not usually warrant fungicide control. Raking and removing fallen leaves in fall will reduce the amount of overwintering inoculum that would be available to infect the trees next year.
Images (click to enlarge):
Disclaimer: Commercial products are listed for informational purposes only. Virginia Cooperative Extension does not endorse these products and does not intend discrimination against other products that may also be suitable. Due to continually changing laws and regulations, Virginia Cooperative Extension can assume no liability for the suggested use of chemicals contained herein. Always consult the pesticide label, which is the law, and follow label directions and precautions.
