This spring/summer has been particularly tough on many plants, including crab apple trees. The wet cool spring gave fungal leaf diseases a perfect environment to thrive. Even though leaves look bad or are falling off it is not at all likely to kill the tree. If it is a young tree, planted in the last 5 years, be sure to water it weekly through this very dry spell until the ground freezes. It should leaf out just fine next spring.

Paul - Tree Care Advisor volunteer