The protective shell resembles miniature oyster shells. Their eggs hatch in late May or early June. Plants infested include cotoneaster, apple, lilac, spirea, snowball, high bush cranberry and others. The protective shell is pear-shaped and whitish in color. The scales cluster on stems and branches.
Heavy infestations give the bark surface a flaky appearance.
Eggs hatch in mid-May. Plants infested are elm, ash, apple, maple, willow, aspen, and cotoneaster. The covering is oval, flat, and pale to dark brown. In the spring a white cottony egg sac two to three times the length of the scale is produced. The eggs hatch in late June or July.