Untitled Document Apple scab is a disease of apples and crabapple trees caused by the fungus Venturia inaequalis. Symptoms are most commonly observed on the leaves and fruit, but apple scab will grow on petioles and blossoms also. Leaves with several spots turn yellow and drop from the tree.
Infected fruits have brown corky spots with cracks in the fruit.
The fruit matures unevenly and appears deformed. Life Cycle the fungus overwinters in leaf litter and in cracks and crevices on the tree bark. During wet weather in early spring spores produced on the leaf litter and carried by wind and rain to emerging spring leaves. Damage from apple scab is not life threatening to well establish healthy trees. Frequently very susceptible trees are severely defoliated by the middle summer making the ornamental tree aesthetically unattractive.