Brown or black crusty bumps or thick, white, waxy bumps cover nodes, stems, buds, and leaves. The bumps can be scraped or picked off; the undersides are usually soft. Leaves may turn yellow and drop off. In some cases, a shiny or sticky substance coats the leaves. Black sooty mold often grows on the sticky substance.
Apply a horticultural oil or an insecticide labeled for scales, following label directions.