Brownish crusty bumps; thick, white, waxy bumps; or clusters of somewhat flattened yellowish scaly bumps cover stems or leaves. The bumps can be scraped or picked off; the undersides are usually soft. Leaves turn yellow and may drop. In some cases, a shiny or sticky substance coats the leaves. Black sooty mold often grows on the sticky substance.
Spray with an insecticidal soap or an insecticided labeled for bamboo scales in late spring when the young are active. Or spray with a horticultural oil to kill the adults, and hose down the plants the following day.