Hi Richard, thanks for the question.

This looks like an invasion of scale insects.  Your cherry tree is susceptible to scale insects.  There is not enough detail to identify the particular scale; however, it may be prunicola  or white peach scale.  It looks as if the crawlers or out. Managing them can be a challenge and timing is critical. Use dormant oil sprays at the appropriate time (see link).  Insecticides can be used while crawlers are active.  Check out the following links:

Pseudaulacaspis prunicola | Insect & Mite Guide | Center for Agriculture, Food, and the Environment at UMass Amherst

Dormant Oil Sprays for Scales.pdf (unl.edu)

I hope this is helpful.