When applied, these oils suffocate insect and mite pests and their eggs. Thorough coverage is required for effective control. There are summer oils and dormant oils. 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.