Ripens around September 5. Susceptible to fire blight, somewhat resistant to powdery mildew, resistant to cedar apple rust. In South Carolina, the recommended crabapple varieties that are resistant to many common diseases include Adams, Mary Potter, Professor Sprenger, Red Baron and Indian Magic. One of the most common diseases, apple scab, is caused by the fungus Venturia inaequalis . The disease begins in spring as dark, olive green leaf spots less than inch in diameter.
Severe infections can affect the entire leaf, causing it to turn brown and drop from the tree.
Slightly raised, black spots deform the fruits. Rake and remove leaves to reduce early spring infection sources. Apply all chemicals according to directions on the label. Apply all pesticides according to directions on the label. The disease spreads from the cedar to the apple and then back to the cedar.