Scale can be bad news to your trees, shrubs, and groundcover. Scale insects fit their name. They live in very hard shells that look like bits of bark for most of their lives. Hidden in their shells, they latch on and suck sap from plants. Scale bugs are very hard to see and control. They're most vulnerable after they hatch. That's when they crawl to their feeding spots where they will live the rest of their lives, except during a brief mating period.
Scale can be white and cottony masses; brown, crusty bumps; thick, white, waxy bumps; or clusters of flattened yellow scaly masses. The bumps or masses can be scraped or picked off easily. As they feed, leaves turn yellow and may drop. A shiny or sticky material may also cover the leaves and stems. Black sooty mold may develop on the sticky substance.