The eastern redbud is a small tree with a wide canopy and a short trunk. Its pinkish purple flowers and red fruit pods that are present in winter make it a pleasant little ornamental tree--which makes a scale infestation all the more unfortunate. A virulent scale infection can turn the eastern redbud's luscious green canopy yellow and even cause the leaves to drop. And the honeydew trail that scale leaves behind can attract black, sooty mold that can cover the branches if left unchecked.
Make sure that scale insects are the culprit. In their adult stage, scale insects look like small discs or waxy scabs that are often mistaken for part of the tree itself. Newly emerged scale nymphs are mobile for a short period of time when they crawl out from beneath their mother's shell to find a new spot on the tree.
Water your eastern redbud before applying any pesticides. A dry tree is under stress, and spraying it when dry could put it under more stress and temporarily affect its growth.
Spray your eastern redbud with a 2 percent horticultural oil solution as soon as you notice the scale insects. Concentrate on spraying the scales themselves. The horticultural oil actually suffocates them.
Spray crawling scale nymphs with a scale-specific insecticide. Scale nymphs emerge in late spring and early summer. As soon as you spot them, spray an insecticide like Bug Buster. Concentrate on the areas where you have seen scale activity.
Switch to a slow-release fertilizer with zero nitrogen. Eastern redbuds produce their own nitrogen. If it is also present in the fertilizer, your redbud will likely produce excessive new growth, which scale insects thrive on.