Oystershell Scale (Lepidosaphes ulmi)

From: Ostry, Michael E.; Wilson, Louis F.; McNabb, Harold S., Jr.; Moore, Lincoln M. 1988. A guide to insect, disease, and animal pests of poplars. Agric. Handb. 677. Washington, DC: U.S. Department of Agriculture. 118 p.

Importance- This insect sucks sap from the stems and branches of Populus and many other tree species. Outbreaks are sporadic; when populations are large, branches or scattered trees die.

Look For: Dead and dying branches or trees. Chestnut brown flat scales (one-eighth inch long), shaped like an oyster on the bark. Often in large clusters they appear as a crust on the bark.

Cluster of oystershell scales Photo by William M. Ciesla, Forest Health Management International

Biology- Eggs overwinter beneath the female scale, and crawlers hatch in spring. After nymphs settle down on the bark and grow into adults by late summer. Each year one generation occurs in the North, two in the South.

Monitoring- Inspect trees for scales any time of the year. Consider control only when 10 percent of the trees are heavily infested and shoots are dying.

Oystershell scales Photo by USDA Forest Service - Rocky Mountain Region Archives

Control:

• Prune and destroy infested branches.
• Spray individual infested trees with an insecticide recommended for scale insects.