Lepidosaphes ulmi
Pest description and damage Scale insects are small (less than 0.125 inch in length) soft insects that live beneath waxy scales. These insects are often identified by the shape and size of their scales, the description of adult males and females, immature crawler stage, color of eggs, and host plant preferences. The mature insect is approximately 0.125 inch long beneath a brown, or gray scale that is usually elongated and slightly curved like an oyster or mussel shell. Oystershell scales are found on trunks, branches, and twigs of many broad-leaved deciduous plants. They occur less frequently on the leaves and other plant parts. Scale infestations often are limited initially to isolated colonies on single branches or twigs. Newly emerged crawlers look like bright white pimples on the bark. Stressed trees where the scales encrust entire branches suffer the greatest damage.
For biology, life history, monitoring and management
See:
Ash (Fraxinus)-Oystershell scale
See "Scale insect" in:
Management-chemical control
See Table 1 in: