Once the insects are under the protective covering, most insecticidal applications are ineffective. Heavy scale infestations weaken the trees or shrubs. Infestations isolated on individual branches may be pruned from the plant in an attempt to reduce scale populations. Horticultural oils are petroleum-based products. 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.