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Description
The female scale lives under a gray or brown shell, shaped somewhat
like an oyster shell. The males produces a smaller white covering
and can be quite numerous. The eggs laid by the female are usually
orange-yellow. The newly hatched crawlers are also orangish is appearance.
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Life
History
The female scale is usually found along the stems and leaf
veins of the host plant. When infestations are heavy, the
whole plant may be whitened by the smaller male scales. The
scale overwinters as a fully-grown, fertilized female. Eggs
are deposited in early spring beneath the dark-colored scale
covering and hatch over a period of two to three weeks in
early June. The nymphs crawl to other parts of the host plant
or are blown to other susceptible hosts. There are at least
two generations per year.
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Click on image for larger
version
Figure 1. Euonymus Scale
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Damage
The euonymus scale can cause complete defoliation and even death
of the plant if infestations are heavy. It is particularly a problem
on evergreen euonymus such as Euonymus japonica, but E.
kiautschovica (=sieboldiana) appears to resist heavy attacks
of euonymus scale.
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Click on image for larger
version
Figure 2. Euonymus Scale on Euonymus
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Nonchemical Control
Currently, the Korean lady beetle is being evaluated as a
predator of the euonymus scale, but is not available commercially.
Pruning out heavily infested branches may help in reducing
scale populations. Planting less susceptible varieties can
reduce the need for scale control.
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Chemical
Control
Control of the euonymus can be achieved by applying a crawler spray
in early June with 4 applications 10-12 days apart. Dormant oil
applications may also be applied for control of overwintering females.
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