Scab

Scab is a disease of ornamental and fruit trees. Trees that are commonly affected include crabapple, hawthorn, mountain ash, apple and pear. This disease is more common in cold, wet weather. Some symptoms are listed below:
• Lesions on leaves, mostly on the upper leaf surface
• Lesions may be circular with feathery edges, may have an olive green to black color
• They may be about ½” diameter