Most people do not realize they have scale until the plant is badly infected. The scales are normally under the leaves and hard to spot. The best thing to do is inspect your euonymus during the growing season for signs of scales and if you find them, treat it early. There are volick oil sprays and systemic insect controls available to kill scale. You may have to treat the plant several times. Scale is not easy to get rid of in the garden. Discard any cutting that have scales on them to the trash can for disposal and not in the compost to prevent spreading. Euonymus scale is found all over the United States.
The Creative Gardener