Oyster Shell Scale
The most significant of these pests is the oyster shell scale, so named because it resembles a minute oyster attached to the bark of trees. Aspen, ash, lilac, cotoneaster, willow and poplars are among the many plants in the region highly susceptible to this insect. Oyster shell scales kill, often because of the increased susceptibility to disease caused when the scales sap the plant’s vigor.