Question
We have two ornamental crab apple trees that are 6 years old and approximately 8-9 feet tall.  This spring I noticed that one of the trees has red mounds growing from the tree trunk and branches.  They look like blisters or cankers but are part of the tree itself.  The other tree is showing not signs of this appearance.  Neither tree has flowered at all to date.  What is wrong with the tree and what can I do to help it and prevent spreading to the other tree?  Thank you for any and all assistance you can provide.

Answer
If the red mounds you describe are rather corky and round in appearance, I would think the tree had black knot, which is a fungal disease of many fruit type trees.  Black knot galls will turn black with age and will be hard and appear like dead tissue.  Pruning off branches that have this problem is one solution.  Use a general purpose fungicide like Daconil and treat the entire tree.  Treat the other trees as well as this disease can move to healthy trees.  Let me know if does no seem to be the case and I will pursue a different path.  Good Luck.