Twigs and stems are covered with powdery white or shiny brown crusty bumps, 1/2 inch in diameter, or soft masses of purple insects. Stems that are normally light green may appear enlarged and purple or whitish. The crusty bumps can be scraped or picked off; the undersides are soft. Leaves may be yellowing and smaller than normal; trees may be weakened or killed. A shiny, sticky substance usually coats the leaves. A black sooty mold often grows on the sticky substance.
Spray with an insecticide labeled for scale. Early the following spring, before new growth begins, apply a dormant oil spray to control overwintering insects, following label instructions.