Hail can injure apple fruit, shoots, and limbs. The extent of the injury usually depends on the size of the hail, its shape, and the duration of the event. Injury can range from torn or shredded leaves and small dents that don’t break the fruit skin to so severe that an entire crop is lost because of physical damage. In some cases, replacement of trees will be necessary, especially when young trees have large amounts of bark injury. Fungicide protection of injured tissues may be necessary immediately after a hail storm to prevent fungal colonization of wounds. Orchards with fire blight may be devastated by the disease following a hail storm because the pathogen rapidly colonizes wounds. In orchards with a history of fire blight, and where there is no resistance to streptomycin, apply a streptomycin application within the first 24 hours following a hail event. See this article, Hail Injury on Apple Trees and Fruit, for photos and more information on hail injury.
Answer provided by Alan R. Biggs, West Virginia University.