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Mussel Scale


Mussel Scale

Usually appear in

All Year

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Caused By:-     The Scale insect Lepidosaphces Ulmi


Mussel scale(Lepidosaphces Ulmi) is also known as the oystershell scale, but in New Zealand the name Oystershell scale is reserved for Quadraspidiotus ostreaeformis. It has a shape that resembles a saltwater mussel.
It is found on twigs at the base of the leaves of Buxus and on fruits, such as apple.
This insect lives under the scale which is about 3-4 mm and apart from the rare winged adult male and the tiny six-legged crawlers, all stages are immobile on the bark of the infected tree. The adult female lays eggs beneath its scale covering. After laying the eggs the female dies and the eggs overwinter until the next spring. after hatching the crawlers (or first instar nymphs) which are about 0.3 mm long, elliptical, and creamy-white to yellow crawl to new sites or are blown to other trees. After finding a suitable feeding site, the crawler inserts its stylets into the plant and immediately begins to suck the sap to produce its scale covering.
The adults are usually clustered together and in severe infestations may cover the bark of infested branches completely. If the scales are prised open in the winter the white mass of eggs can be seen.
Mussel scale has worldwide distribution but does not have quarantine significance and it is sufficiently different in appearance that it should not be confused with the major quarantine scale pest, San Jose scale.
Picture by William M. Ciesla, Forest Health Management International,
See these other Scale insects Azalea Bark, Azalea Cottony, Beech Bark, Brown, Eucalyptus Gumtree, Euonymus Mussel, Hemispherical, Horse Chestnut, Hydrangea, Juniper, Oleander, San Jose, Scale, Soft, Viburnum Cushion, Wisteria, Wooly Vine.


Spraying with an insecticide in early spring when the crawlers are hatching will control this pest. In the winter a tar oil wash will help to get rid of the hibernating eggs.

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