Scale is a name applied to 8,000 different species of insects. While they vary greatly in appearance, Scales are significant crop and tree pest. Female Scales develop a protective covering, and become immobile (sessile) and attached to the plant they are feeding on.
Scales are divided into two groups: armored and soft. Armored Scales are less than ⅛ inch in diameter and have a waxy covering that is separate from the insect body. Soft Scales, such as Cottony Cushion Scale, are less than ¼ inch in diameter and have a waxy layer that is part of the insect body.
Scales suck the juices from plants causing reduced growth, yellowing foliage and premature leaf drop. Scales also excrete honeydew, a sweet, sticky substance that attracts Wasps, Ants and Bees and can serve as a medium on which Sooty Mold can grow. (See Sooty Mold.)
Sprays to control Scales are most effective during the immature crawler stage, which usually occurs from late winter to early summer. Your local cooperative extension can provide precise spray timing.
Various types of Scales are found throughout the United States.