Hello,

This is an insect called euonymus scale. Right now the scale has a protective coating, the tiny white ‘scales’ that you see. They are not very vulnerable to insecticides right now. 

A systemic insecticide, such as a soil drench  of imidacloprid around the root zone this fall can kill the young crawlers when they hatch next spring.

Here are details on treatments-

https://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/adv...

https://hort.extension.wisc.edu/articles/euonymus-scale/

What you can do now is prune out the heaviest infested branches where possible, and keep the plants watered the rest of the season during dry times. This is an evergreen plant so it is important to water into October if the weather is dry, up to when the ground freezes.

The white scales remain after the adults die, so you will continue to see these after treatment. They can be gently brushed off as described in the second link above.