Answer: Sounds like a classic case of apple scab, a fungus that causes problems with apple trees, but can affect crabapples as well. The symptoms include tiny water-soaked spots on leaves that eventually spread and cause the leaves to turn an olive-green color. Ultimately the leaves curl, turn brown and fall from the tree. This disease overwinters on the stems and branches of the tree, so the fungus is ready to attack as soon as the leaves unfurl. A lime-sulfur (Bordeaux) spray will halt the spread of this fungus. You'll have to spray a couple of times to get complete protection. Read and follow the label directions.
Q&A Library Searching Tips