Growth on cherry trees
These are scale insects. They suck the contents out of plant cells. Scale insects have a covering to protect them, like a turtle. The fuzzy white ones are the males. Scrub the bark with a stiff-bristled brush (but not a wire brush). This will knock the covers off the scales. Then spray with insecticidal oil or soap. Be very careful of air temperature when you spray. Read the label closely. This also exposes the scale insects' bodies to beneficial predatory insects.
When the tree is dormant this fall through winter, spray again with a dormant oil.
Here is more info on scale insects: http://extension.umd.edu/hgic/plants/armored-hard-scale-trees-and-shrubs
Thank you very much! It looks much better after following the advice you gave