Armored scales are so named because they secrete a protective cover over their bodies. Most species overwinter as eggs beneath the female cover. In spring, eggs hatch into tiny mobile crawlers which migrate to new feeding sites. After a few days, crawlers settle, insert their mouthparts, and begin feeding. Soon they secrete a protective cover and lose their legs.
Large populations can build up unnoticed before plants begin to show visible symptoms.
Our most common armored scale pests are described and illustrated below. San Jose Scale Mature scales are circular, slightly convex, and smoky black. Under a magnifying glass, a conspicuous, dark gray, concentric ring is visible. San Jose scale is perhaps the most widely distributed and most destructive scale insect pest of fruit trees, shade trees, and ornamental shrubs in the United States. Over 60 host plants are known, including apple, pear, peach, cherry, ash, poplar, lilac, elm, willow, pyracantha, and cotoneaster.