Oystershell scale, Michigan trees, shrubs

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IPM Scouting in Woody Landscape Plants

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Oystershell scale - Lapidosaphes ulmi

This armored scale has two forms (lilac and apple) that attack numerous hosts, including ash, lilac, maple, willow, crabapple, linden, elm and others. It overwinters as eggs, which hatch in mid-May, when black cherry or blackhaw viburnum are in full bloom. No honeydew is produced.

Management: Target first generation crawlers with insecticides or oil. The first generation of crawlers should have emerged by the time Spirea x vanhouttei is in full bloom, in mid- to late May. There is one generation of the lilac form and two of the apple form per year. Twice-stabbed lady beetles and parasitic wasps are natural enemies of oystershell scale.

Scales with exit holes caused by emerging parasitic wasps.


Symptoms of oystershell scale include dieback of branches and twigs, yellowed or undersized foliage and an unthrifty appearance, as shown on this Carolina silverbell.	Brown-to-grayish oystershell shaped scales, about 3 mm long, form a crust on the bark.

Additional information

MSU Diagnostic Services for assistance in pest identification.
MSU Landscape Alert newsletters for information about the current growing season, pest concerns and plant advice.

This information was developed from A Pocket IPM Scouting Guide for Woody Landscape Plants by Diane Brown-Rytlewski. Purchase this in a pocket-sized guide for reference in the orchard from MSU Extension (publication E-2839).

The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the Michigan Agricultural Experiment Station, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.
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Updated 10/11/07