Answer: There are a number of pests and diseases that can attack a flowering crab apple just as they can attack ordinary apple trees. Some cultivars have better resistance than others to certain of these diseases. Some problems may require dormant season spraying for control. I would suggest you work with your local nurseryman to determine specifically what is affecting your tree and then based on that decide how to proceed. I hope it is nothing too serious.
Q&A Library Searching Tips