On many ornamental plants, scale insects are the most serious pests, and most ornamentals are susceptible to one or more species of scales. Scales cause damage by sucking the juices from the plants. Heavily infested plants appear unhealthy and produce little new growth. Scales feeding on the undersides of leaves may cause yellow spots to appear on the top sides, and these spots progressively become larger as the scales continue to feed. If the scales are not controlled, leaves will drop prematurely, sometimes killing portions of twigs and branches.
Scales also feed on trunks and stems of plants.
Female scales never possess wings and are disseminated primarily by infested plant stock. They are spread to a lesser extent in the crawler stage by man, birds, other animals and wind currents. The armored scales secrete a waxy covering over their bodies. This covering is not an integral part of the insect s body, but the scale lives and feeds under this cover that resembles a plate of armor, hence the name. The female armor is larger than that of the male, while the shape and color may be similar to distinctly different, depending upon the particular species.