Answer: There are in fact many types of scale insects. What they have in common is their method of protecting themselves: they all develop either a soft or hard protective covering over their body. Male insects are mostly winged. The females, which are wingless, move from plant to plant via wind, physical contact, birds or man. The females attach themselves to a plant and remain there until they die and often for a number of years afterwards. If you observe a large number of scales on a plant, you may not have a heavy infestations. These may be the scale coverings of insects that have died.
In the fall, after mating, the female scale insects create their overwintering protective covering. Scale coverings range in size, shape and color. The pine needle scale insect creates a white, waxy, elongated covering. This pest should not be confused with the wooly aphid, which creates a wooly, white fuzzy round covering. The poplar scurfy scale appears as a small, scabby growth which can easily be scraped off the stems with a knife or fingernail.
While it is under its protective covering, the female lays eggs. In spring, the eggs hatch and the unprotected larvae (crawlers) emerge. The crawlers move out from under the protective scale and begin feeding on their own. The actual date of emergence varies with each type of scale insect.
There are a number of insects which prey on scale insects. Beneficial predator insects such as braconid wasps and lady beetles prey on both the larvae and eggs of scale insects. Although the population of these beneficial insects is large, the harmful scale insect population may be larger, and therefore control may be necessary.
Insecticidal soap should prove effective if applied to crawlers before they mature. Chemical control is effective only on the unprotected crawlers (larvae). When they are still under their protective covering, the crawlers are quite resistant to chemical attack. Therefore, in order to control them chemically, you need to know when the crawlers emerge from the coverings.
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