The leaves and fruit (especially the calyxes on the bottom of the fruit) are very suggestive of crab apples.  The disease looks like cedar apple rust.  The amount of rust disease varies from year to year, closely related to weather in the spring.  Here is our website info on it: http://extension.umd.edu/hgic/rust-diseases-trees-and-shrubs
The infection period was early in the season. Fungicide applications need to be applied when leaves are starting to expand in the spring. No control measures are applied at this time of year.
 
ECN