WSU Extension


Common Insects & Mites : Oystershell scale
(revision date: 4/14/2015)

Oystershell scale is one of many armored scales that attack landscape plants. They are usually found on the bark of trunks, branches, and twigs. Rather small and flat with hard shells, these scales blend well on the bark they feed upon. Their resemblance to an oyster is enhanced when they become numerous, because clustered they resemble a bed of oysters. Oystershell scale produces little or no honeydew.
Management Options

Non-Chemical Management
  • Lady beetles, parasitic wasps and other natural enemies help control scale populations outdoors. Avoid use of broad-spectrum insecticides which kill these beneficials.
  • Prune and destroy heavily infested twigs or branches, if practical.
Select non-chemical management options as your first choice!

Chemical Management

Scout for crawlers. Certain insecticides are effective for control of scale crawlers only. Apply to control the immature crawler stage, usually in late spring to early summer. Refer to the fact sheet for oystershell scale on a particular host for registered pesticides.

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Caption: Oystershell scales
Photo by: Unknown