Problem: Fruit Scab
This disfiguring disease is caused by a fungus (Sphaceloma perseae) that is carried over from one season to the next on stem and leaf lesions. Young fruits are usually infected just after the petals fall from the flowers. As fruit ages, it becomes more resistant to infection, but it does not acquire immunity until it is more than half-grown.
Spray the entire tree with a fungicide labeled for fruit scab, following label directions.