It's up to you, but crape myrtles are quite capable of sprouting out from the base even if everything above is killed.

@bengz6westmd, thanks! If I cut all the branches now, next spring will the scales come back?

in northern VA crapes are over planted - every suburban yard has at least one and they line roadway medians. As a result scale is rampant. I stopped growing crapes because I don't want to deal with scale (if it's endemic in your area it's going to keep coming back) and there are many other lovely small trees to choose among.

Why not take the garden hose and blast all the scale off?

The black is most likely the black sooty mold that forms when scale exudes its honeydew.

I had this on my Natchez White crepe this Spring. I blasted it off with the water hose over and over and over again. Don't see any now but it may come back next Spring.

treatment recommended is to apply a systemic insecticide containing imidacloprid late march through may once per year and also treat nearby uninfested crapes.

sourced from auburn university extension service. see link below.

crape myrtle bark scale

@jeff_al, thanks so much for the information. Will follow and spray the trees next March

Really a bummer about this bark scale.