Lilac: Oystershell scale

categories: Lilac Lilac Insects Ornamentals Shrubs

revision date: 2024-06-05 08:28

Severe oystershell scale infestation on twig.
Severe oystershell scale infestation on twig
Photo by: Unknown


Oystershell scale insects are usually found on trunks, branches, and twigs. They occur less frequently on the leaves and other plant parts. The mature scale is approximately 1/8″ long, striped with grayish and brown bands, and elongated like an oyster or mussel shell. Infested plants may wilt or show off-color foliage. Scales can be spread from plant to plant by birds, people, wind, or insects.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

  • In minor infestations it may be possible to wipe scales off branches.
  • Where practical, prune and destroy heavily infested branches.
  • Natural predators and parasites help control scale populations, but usually not soon enough to prevent damage to plants.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

  • Scout for crawlers. Insecticide applications can be effective when applied to control the immature crawlers stage, usually in late spring to early summer.
  • Oils are effective in the delayed dormant period. Use superior type oil sprays only on overwintering nymphs.
  • Homeowners should not make foliar applications to trees over 10 ft tall.
  • Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Approved Pesticides

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.