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Euonymus Mussel Scale


Euonymus Mussel Scale

Usually appear in

Summer to autumn

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Caused By:-     Unaspis euonymi


Adult euonymus scale insects appear as small white or brown, immobile spots on stems and leaves.
The males males about 2mm long and females about 4mm oval and brown. The adults have wings and can fly to mate and infect other plants. The insects on leaves are mainly the whiteish male, the brown females prefer the stems.
Although this insect mainly attack Euonymus it can also infests Celastrus, Camellia, Eugenia, Holly, Pachysandra and Twinberry. Depending on the temperature throughout the year this scale insect can have up to three generations in one year.
The females lay eggs under their protective shell, and the tiny crawlers hatch and emerge from the mother's protection scale from spring onwards. The scale insects crawl about before inserting their mouthparts to start sucking the sap from the plant, then they start to grow and secrete their waxy scale.
The leaves initially are spotted yellow which gradually becomes yellow before dropping off.
Euonymus scale is easy to miss until it has damage the plant severely. Some plants can die after several years of severe infestation.
Picture by John A. Weidhass, Virginia Polytechnic Institute and State University,
See these other Scale insects Azalea Bark, Azalea Cottony, Beech Bark, Brown, Eucalyptus Gumtree, Hemispherical, Horse Chestnut, Hydrangea, Juniper, Mussel, Oleander, San Jose, Scale, Soft, Viburnum Cushion, Wisteria, Wooly Vine.


These insects are difficult to eradicate because their waxy covering. This covering protects them from insecticides.
Before they settle down, the crawler stages of these insects are much more susceptible to application of knock down insecticides.
Systemic insecticides are best applied from late spring onwards.
Heavily infected parts of the plants are best pruned out as strong winds can blow the insects to other nearby plants.
Biological control is possible as the insects are susceptible to many predators, including lady beetles, green lacewing, and predatory mites, but these predators cannot control large infestations.
Another strategy to control this pest is to spray with a plant oil wash in winter.

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