Euonymus Scale
Unaspis euonymi
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.
Life History
Figure 1. Euonymus
Scale
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.
Damage
Figure 2. Euonymus
Scale on Euonymus
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.
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.
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.