Entire leaf may turn yellow and red and fall off. Avoid wetting the foliage when watering. Rake and dispose of leaves. Same as for Flowering Crabapples . Leaves remain attached.
Bacteria enter through blossoms.
Prune out diseased shoots well below visible infection. Same as for Flowering Crabapples . Cankers on large branches and trunk. Fungi attack weakened trees. Prune out dead and diseased branches in summer.