Ornamental cherry tree
Some of these growths look like lichen and some like fungus. In both cases, they are probably indications of a problem rather than the cause of a problem. Lichen indicates slow growth and moisture. It is telling you that a portion of your tree has stopped growing but doesn't tell you why. The fungus is breaking down dead tissue and is also telling you that there is damage to your tree that should be examined.
You should have a certified arborist examine the tree to determine what has caused the damage and what can be done to save the rest of the tree. You can find a certified arborist that works in your area through the International Society of Arboriculture (www.isa-arbor.com).