Frequent watering and fertilization favor disease development. 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.