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Euonymus Scale Fact Sheet
Fact Sheets
> Insect Fact Sheets > Euonymus
Scale
The euonymus scale, Unaspis euonymi (Comstock),
is an exotic armored scale of Asian origin that feeds on the foliage
and stems of woody landscape plants in Pennsylvania. It has become
a major concern in many landscapes because, without treatment, heavy
scale infestations will reduce photosynthesis, stunt plants, cause
leaves to abcise, and kill all or part of the plants.
Plants Attacked
Common
Problem |
Wintercreeper euonymus |
Euonymus fortunei |
| |
American Bittersweet |
Celastrus scandens |
| |
English ivy |
Hedera helix |
| |
Japanese Pachysandra |
Pachysandra terminalis |
| |
|
|
| Occasional Problem |
Boxwood |
Buxus spp. |
| |
Privet |
Ligustrum spp. |
| |
Honeysuckle |
Lonicera spp |
| |
Canby Paxistima |
Paxistima canbyi |
| |
Holly |
Ilex spp. |
| |
stone fruits |
Prunus spp. |
| |
Daphne |
Daphne spp. |
Insect Identification
 |
Male and female Euonymus
scale -- Photo courtesy of Michael Masiuk
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| Euonymus scale crawlers
-- Photo courtesy of David Shetlar |
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Females are dark brown or gray, about
1/16" long and pear-shaped. They are more commonly found
on the stems of host plants. Males are 1/32"long, narrow,
white with a yellow cap at one end, and often more abundant than
the females. They are easily seen on both the stems and leaves.
Eggs are tiny and yellow, and the crawler stage is also tiny and
yellow.
|
Life History
| Winter |
Fully grown, fertilized adult females. |
| Spring |
Eggs are laid in early spring and hatch over a two to three
week period in early June. The young nymphs crawl to other parts
of the host plant before settling down to insert their mouthparts
to begin feeding. Once settled, they secrete their waxy protective
covering.
|
| Summer |
Males emerge as tiny, two-winged insects and mate with
the females, which shrivel after they've laid eggs under their protective
shell. The second brood hatches in late summer. |
| Fall |
Mature females and settled crawlers are found on stems
and leaves. |
Damage Symptoms
 |
| Euonymus scale on
stem -- Photo courtesy of
Michael Masiuk |
The first visible damage is yellow spotting on the leaves. Variegated
forms of Euonymus sometimes exhibit a pinkish-red color in the
leaves. On heavily infested plants, thousands of mature female
scales encrust the stems and reduce photosynthesis. This results
in stunted plants and leaf drop, and can kill all or part of the
plant. |
 |
 |
 |
| Male Euonymus scales (white hyphens) on the
foliage of Euonymus fortunei |
Multiple layers of euonymus scale encrusting
the stems of Euonymus fortunei
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Euonymus fortunei showing branch dieback from
a severe infestation of euonymus scale
|
 |
 |
Servere infestation of Euonymus scale on Euonymus
fortunei completely killing the shrub
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Yellow spotting on Euonymus foliage resulting
from euonymus scale feeding |
Mangement Options
| Biological |
The lady beetle Chilocorus kuwanae was introduced by
the USDA for control of Euonymus scale from the early 1980's through
1995. This predator has been able to suppress heavy scale infestations
to lower levels in sunny locations. Due to the reproductive ability
of the scale, biological controls can not always keep the scale population
level at acceptable levels. |
| Mechanical |
Where possible, prune out and destroy infested branches. |
| Cultural |
Be sure Euonymus plants are
free from scale when you buy them. |
| Resistant Varieties |
Research at Auburn University indicates that spreading
euonymus, (Euonymus kiautschovicus), dwarf winged euonymus (Euonymus
alatus 'Compactus'), and winter creeper euonymus (Euonymus fortunei 'Acutus'), are more resistant to heavy attacks by this pest than other
varieties. Spreading euonymus, (Euonymus kiautschovicus), is marginally
hardy in many parts of Pennsylvania and is listed as hardy to zone
5. The cultivar 'Paulii' is reported to have the best cold hardiness
for this species. |
| Chemical |
Control of euonymus scale can be achieved by applying a registered
pesticide to the newly hatched crawlers. Thorough penetration
of dense foliage is essential to get adequate control, particularly
on scales located at the base of the plant near the ground on
vining type euonymus. Horticultural spray oils kill the crawler
stage that is present at the time of application. Good control
is achieved only with thorough coverage.
Control
measures for eunoymous scale. |
 download
Euonymus Scale Fact Sheet
Authored by: Michael Masiuk, Commercial Horticulture
Extension Agent, Allegheny County, Pennsylvania
Last Updated: Tuesday, February 11, 2003
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