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The citrus scale insect is generally found on the trunk, foliage, and, sometimes, fruit. It looks like small crusty, waxy, or smooth bumps about a ¼ inch or smaller in size. Several of the bumps can be clustered together making the scale look larger. The leaves of infested trees yellow and often drop, and a shiny sticky substance can coat the leaves. The presence of citrus scale can also cause black sooty mold to grow on the sticky (honeydew) substance.
The scale insects harm the tree by constantly sucking sap from the tree’s vascular system, thus placing stress on the tree and reducing its natural growth and fruit production cycles.
Scale insects over-winter on the trunk and twigs of the tree and do not move throughout their lifecycle, once they are established. In the spring or early summer, juvenile nymphs emerge and slowly move to other areas of the tree. This movement in the nymph stage is the only time that they are mobile during their lives, it is also the time that they are most vulnerable to insecticides.
In the fall and early spring, spray the tree with Horticultural Oil Insect Spray, which will serve to suffocate established scale. In the spring and early summer, when the nymphs are active, spray the tree with Take Down Garden Spray. Repeat the spraying every ten to fourteen days.