Scale Commonly Encountered in Maryland
Landscapes and Nurseries
Integrated Pest Management for Commercial Horticulture
extension.umd.edu/ipm
Introduction
Scale are sucking insects that insert a needle-like
mouthpart, composed of four slender stylets, into
plant tissue and remove plant juices. This feeding
causes stunting, reduced vigor and sometime dieback
of plants. Scale were once classified in the order
Homoptera, but have now been moved into the order
Hemiptera. Scale insects feed on plants through
a long stylet bundle (straw-like mouthparts) that
is inserted into the plant. Armored scales pierce
plant tissue and suck up cell contents from stems
or leaves, depending on the species. They suck out
cell contents from conductive tissue in the wood and
the chlorophyll-containing cells of leaves. Armored
scales do not produce honeydew. Early damage
symptoms of armored scale feeding are chlorosis of
the foliage immediately surrounding the feeding site
of each scale. If many scales are present, this may be
followed by browning and defoliation. Honeydew
deposits are usually the first signs of feeding by
soft scales and mealybugs. A black sooty mold
grows on the honeydew that may cause a blackened
appearance to the foliage, twigs, branches, and
any other surface beneath an infested plant. They
do not suck out chlorophyll, so there is no sign of
chlorosis around their feeding sites. Soft scales and
mealybugs generally feed on the sap in the phloem
of the plant on stems and along leaf veins. Sunken
areas in bark are symptoms of pit scale in the family
Asterolecanidae.
Lines in calendar tables for each
scale indicate when crawlers are
most likely to be active.
Pest Alert - 2011
Azalea Bark Scale (Acanthococcus azaleae)
Family Erioccicdae
APR
MAY
JUN
JUL
AUG SEP
OCT
Plants Damaged: This scale is a pest of azaleas
and rhododendrons. This scale has been reported
on hawthorn, Andromeda, poplar, willow and
ornamental cherry trees.
Damage Symptoms: Azalea bark scale has become
recognized as a prominent pest of azaleas. Infested
plants usually appear chlorotic and unthrifty. Infested
plants are often covered with sooty mold, a black
fungus that grows on the honeydew excreted by the
azalea bark scales as they feed. Eventually twigs may
die back.
Life Cycle: As the female azalea bark scale matures,
it secretes white, waxy threads, which become
felted or matted into a thick covering over its entire
body. Females lay eggs in this white wax. As the
female lays eggs, its body shrivels gradually as the
egg sac fills with eggs. Eggs are laid in May. They
hatch in central Maryland in late May to early June.
Individual crawlers are active and moving for 12 –
24 hours. New crawlers continue to emerge over
a couple of weeks. There are two generations in
Maryland. This new generation matures during the
Life Cycle: This scale overwinters as second instars
and molts and matures to 3rd instars in early spring.
The nymphs of this scale will migrate out onto the
foliage in June and feed through the summer. In the
fall the immatures will migrate back to the twigs
where the females overwinter.
summer and produces eggs in September. Mature
females tend to feed in crotches and on twigs. Adult
males, two-winged and tiny, tend to feed on the
leaves. Azalea bark scale overwinters as immatures in
the forks of the twigs.
Control: If the population is low and damage is
minimal, look for beneficial insects which do a good
job controlling this insect. If necessary, apply a
dormant spray for overwintering nymphs on twigs.
In summer when crawlers are active, you can use a
summer rate (0.5 – 1.0%) of horticultural oil.
Monitoring: Look for copious amounts of honeydew
in late May and early June. Look for the oval-shaped,
yellow-bodied crawlers in June.
Control: Apply horticultural oil in March to
early April to kill overwintering females. When
crawlers are out, use pryriproxyfen (Distance) or
buprofezin (Talus) with 0.5 – 1% oil. Another option
for controlling soft scale is to use a soil injection,
basal flare, or soil drench of a systemic insecticide,
dinotefuran (Safari, Transtect). This material takes 20
- 30 days to be taken up by the plant before it begins
to control the scale. It is very effective against soft
scale insects such as calico scale.
Calico Scale (Eulecanium cerasorum),
Family Coccidae
APR
MAY
JUN
JUL
AUG SEP
OCT
European Fruit Lecanium (Parthenolecanium
corni), Family Coccidae
APR
MAY
JUN
JUL
AUG SEP
OCT
Plants Damaged: Calico scale is a general feeder
and can be found on many nursery and landscape
plants including dogwood, honeylocust, magnolia,
maple, sweet gum, tuliptree and ornamental fruit
trees.
Damage Symptoms: Calico scale covers the
branches and leaves of the host plant and feeds on
the phloem tissue. The plant may be covered in sooty
mold as a result of the large quantities of honeydew
produced by the calico scale. In large numbers,
feeding can result in branch dieback.
Identification: This white and dark brown calico
scale is about 1/4 inch in diameter and is brightest
when it reaches maturity and then darkens. First
instar nymphs start out pinkish and become yellowish
as they enlarge. Overwintering immature females are
oval, flattened, and light to dark brown and have a
hard waxy coating. Just before egg hatch the covering
is white with gray-blue patterns.
2
Plants Damaged: This soft scale occurs on many
shade tree species including hawthorn, red maple,
pyracantha, and other plants in the rose family. The
European fruit lecanium is a common soft scale insect
pest of shade trees and other woody ornamental
plants in Maryland. This species feeds on a wide
range of host plants and is considered polyphagous.
Populations of this pest build up quickly so
monitoring for this pest on potential host plants is
important.
Damage Symptoms: Feeding damage may cause
curled, chlorotic foliage that may drop prematurely.
Smaller infested branches are weakened due to
feeding injury or in some cases may be killed. Also,
when this soft scale species is feeding on leaves and
twigs, a large quantity of honeydew is secreted.
tan. This scale can reproduce quickly with over 1,000
eggs per female. There is one generation a year.
Crawlers begin to appear in mid-June. The scale tends
to accumulate on the undersides of foliage.
Life Cycle: The 2nd instar females overwinter on
the branches. The females will start to swell-up in
May and crawlers emerge in late May to early June.
Nymphs move out onto foliage where they feed in
summer and migrate back to the stems and trunk to
overwinter.
Monitoring: Look for sooty mold and honey dew on
the foliage. Examine the undersides of leaves for the
white cotton-like sacs.
Control: Wait for eggs to hatch and then treat with
pyriproxyfen (Distance) or buprofezin (Talus) mixed
with 0.5 - 1% horticultural oil. Another option
for controlling soft scale is to use a soil injection,
basal flare, or soil drench of a systemic insecticide,
dinotefuran (Safari, Transtect).
Monitoring: Look for sooty mold growing on the
honeydew excreted on the foliage and branches.
Inspect branches using a 10 -16X magnifier for
crawlers
Cottony Cushion Scale, (Icerya purchase
Maskell), Family Margarodidae
Control: Using pryriproxyfen (Distance) or
buprofezin (Talus) with .5 – 1% horticultural oil
applied when crawlers are active gives good control.
Another option for controlling soft scale is to use a
soil injection, basal flare, or soil drench of a systemic
insecticide, dinotefuran (Safari, Transtect).
APR
MAY
JUN
JUL
AUG SEP
OCT
Cottony Camellia/Taxus Scale (Pulvinaria
floccifera), Family Coccidae
APR
MAY
JUN
JUL
AUG SEP
OCT
Plants Damaged: This large scale attacks a wide
range of woody and herbaceous plants including fir,
maple, boxwood, cedar of Lebanon, citrus, cypress,
elm, laurel, locust, magnolia, nandina, Boston
ivy, pear, oak, rose, and willow. It also attacks the
herbaceous plants sage and verbena.
Damage Symptoms: By removing sap from the
plant this scale causes foliage to yellow and stems to
die back. Large amounts of honeydew are produced
with sooty mold often growing on the honeydew.
Plants Damaged: Taxus yews, camellia, holly,
rhododendron, Japanese maple, English ivy, and
mulberry.
Damage Symptoms: Yellowing of foliage and
dieback of plant in severe infestations. This soft scale
produces large amounts of honeydew on which sooty
mold will grow.
Life Cycle: Adult females are oval and yellowish
3
Life Cycle: This scale was not believed to be winter
hardy in this area, but there are indications that with
the milder climate the scale is now being found on
outdoor plant material in some areas. We had samples
from Prince George’s County and D.C. where the
scale has overwintered. The large white, elongated
ovisac with its distinct ridges is very noticeable.
Inside the sac are hundreds of bright red oblong eggs.
This scale is also unique in that it is a hermaphrodite.
There are multiple, overlapping generations per year.
After hatching the crawlers move to the foliage. This
scale in mobile in all life stages and the scale will
migrate back to stems and the trunk during the winter
just before foliage drops in the fall.
foliage. Heavy infested plants are chlorotic. Dieback
occurs when populations are high.
Life Cycle: This scale overwinters as second instar
females. Adults occur in spring in March and April.
Females lay eggs in June with crawlers appearing in
June through early July. There are two generations
per year. Adults of the second generation are present
in July and crawlers are present in late August
through September. Immatures overwinter on the
needles.
Monitoring: The large elongated, white egg sacs are
the most obvious feature to monitor for this scale.
Control: Soil application of imidacloprid (Merit
in the landscape and Marathon in the nursery) or
dinotefuran (Safari, Transtect) should give good
control. Another option is to apply pyriproxyfen
(Distance) or buprofezin (Talus) to mobile stages
during the summer months.
Monitoring: Look for chlorotic foliage with
yellow spotting or banding on the needles. Look for
overwintering scale on the needles.
Control: A mixture of 0.5 - 1% horticultural oil and
pyriproxyfen (Distance) or buprofezin (Talus) does a
great job controlling this scale. Dinotefuran (Safari,
Transtect) applied as a soil drench also works well.
Control: A soil injection, basal flare, or soil drench
application of dinotefuran (Safari, Transtect) should
give good control. Another option is to apply
pyriproxyfen (Distance) or buprofezin (Talus) to
mobile stages during the summer months.
Biological Control: A lady bird beetle called the
Vedalia beetle (Rodolia cardinalis), has been used to
control this scale.
Euonymus Scale (Unaspis euonymi
Comstock), Family Diaspididae
APR
MAY
JUN
JUL
AUG SEP
OCT
Cryptomeria Scale (Aspidiotus cryptomeriae
Kuwana), Family Diaspididae
APR
MAY
JUN
JUL
AUG SEP
OCT
Plants damaged: Boxwood, camellia, and evergreen
euonymus – especially Euonymus japonica.
Damage Symptoms: Yellowing of foliage, twig
dieback and general thinning of infested plants.
Plants Damaged: This scale is found on many
conifer species including fir, Cedrus, Chamaecyparis,
rarely this scale is found on Cryptomeria, pine,
spruce, Taxus and hemlock.
Damage Symptoms: As the scale draws out sap
from the needles it causes a yellowing spotting of the
4
Life Cycle: This armored scale overwinters as 3rd
instar females. Crawlers appear in May and continue
for 4 – 5 weeks. Second generation adults are out
in July with crawlers present from August through
September. The females are dark brown, oyster shell
shaped and usually found on the stems. Males are
smaller, white and mostly found on the leaves.
Monitoring: Look for chlorotic foliage with
yellowing spotting or banding on the needles. Look
for overwintering scale on the needles.
Control: A mixture of 1% horticultural oil and
pyriproxyfen (Distance) or buprofezin (Talus) does a
great job controlling this scale. Dinotefuran (Safari,
Transtect) applied as a soil drench also works well.
Monitoring: This scale tends to blend in with the
corky ridges on the winged euonymus branches
making detection more challenging until your eye is
trained to pick up the scale covers.
Control: A mixture of 0.5 - 1% horticultural oil and
pyriproxyfen (Distance) or buprofezin (Talus) does a
great job controlling this scale. Dinotefuran (Safari,
Transtect) applied as a soil drench also works well.
Winged Euonymus Scale (Lepidosaphes
yanangicola (Kuwana)), Family Diaspididae
APR
MAY
JUN
JUL
AUG SEP
European Elm Scale (Gossparia spuria)
Family Coccidae
OCT
APR
Plants Damaged: Mainly found on winged
euonymus (Euonymus alatus), but the scale is
reported feeding on maples, ash, lilac and willow.
Damage Symptoms: Yellowing of foliage and
dieback of branched in heavy infestations. Heavily
infested plants have been defoliated during the
growing season.
Life cycle: Third instar females overwinter. Eggs are
produced from late May to early June and are present
through July. Females (as shown in smaller photo)
produce ‘crawler flaps’ (white edge) 2 - 3 weeks
before crawlers emerge.
5
MAY
JUN
JUL
AUG SEP
OCT
Plants Damaged: Elm, mainly European and
American species. Chinese elm appears to be
resistant.
Life Cycle: The female is oval-shaped, soft and
immobile, olive-green to reddish-brown with a white
waxy fringe around the edge of the body. The male
is rarely seen, and looks like a yellow gnat with one
pair of wings. Honeydew is produced by the scale.
This scale has one generation per year. Egg laying
starts in May and continues through July with each
female laying up to 400 eggs. Nymphs, in summer,
migrate to the foliage and establish on the undersides
of leaves, usually along the midrib veins. They use
their stylet mouthpart to pierces into the phloem of
the plant and extract plant juices. At this stage of
development they look very similar to mealybugs. In
the fall the nymphs will migrate back to the twigs and
bark of the tree. The scale overwinter as immatures
in bark cracks on elms (top photo).
for crawlers in July and August in your area. It is
found mainly on the Eastern shore of Maryland where
warmer winter weather allows it to overwinter.
Monitoring: Females are round, brown and
normally found on foliage.
Control: Evaluate whether it is an occasional pest or
a major threat to plant health by the population level
and any dieback occurring. If control is necessary
then a mixture of 0.5 - 1% horticultural oil and
pyriproxyfen (Distance) or buprofezin (Talus) does a
great job controlling this scale. Dinotefuran (Safari,
Transtect) applied as a soil drench also works well.
Monitoring: Look for the settled yellow crawlers
on the undersides of the leaves in June. When
examining the females squeeze the scale between
your fingers and it will be blood red in color.
Control: A soil injection, basal flare, or soil drench
application of dinotefuran (Safari, Transtect) should
give good control. Applications of oil or pyriproxyfen
(Distance) or buprofezin (Talus) are not practical on
large trees.
Felt Scale (Eriococcus quercus), Family
Eriococcidae
APR
MAY
JUN
JUL
AUG SEP
OCT
False Florida Red Scale (Chrysomphalus
bifasciculatus (Ferris)), Family Diaspididae
APR
MAY
JUN
JUL
AUG SEP
OCT
Plants Damaged: Only recorded on oaks.
Damage symptoms: heavy populations can cause
yellow of foliage and slow decline of trees.
Life cycle: Life cycle is not well studied and
recorded. Overwinters as immature females. Females
lay dark red eggs. Crawlers hatch in May to early
June. The scale feeds on new branches and in leaf
axils and is rarely found on leaves.
Plants Damaged: This armored scale feeds on a
wide range of plant material and is found on Acuba,
boxwood, camellia, daphne, euonymus, English ivy,
holly, osmanthus, and lantana.
Damage Symptoms: An occasional pest of
landscape and nursery plants, it has been reported to
cause yellowing and browning of foliage.
Life cycle: The biology in Maryland is not well
understood. Crawlers are present in May and move
out onto the host foliage. It is not known if there is
a second generation per season but you can examine
Monitoring: Examine the base of branches were
populations tend to accumulate.
Control: Pyriproxyfen (Distance) or buprofezin
(Talus) applied at crawler period. Another control
option is a soil injection, basal flare, or soil drench
application of dinotefuran (Safari, Transtect).
6
Fern Scale (Pinnaspis aspidistrae (Signoret)),
Family Diaspididae
APR
MAY
JUN
JUL
AUG SEP
OCT
Damage Symptoms: Besides causing yellowing
of foliage this scale will produce large amounts of
honeydew in spring on which sooty mold grows.
Life Cycle: This scale overwinters as 2nd instar
females that mature in May. The overwintering
females are oval shaped and flattened in profile. In
May the females will swell and become distended.
The eggs will hatch into crawlers sometime in Juneabout the time when catalpa trees bloom.
Plants Damaged: In Maryland this scale is found
mainly on liriope, Rohdea and mondo (Ophiopgon)
grass and ferns but it is a general feeder and has been
reported on camellia, persimmon, peony, and Prunus.
Monitoring: Examine stems of arborvitae and yews
in winter looking for the oval shaped overwintering
females. In May and June, look for honeydew and
sooty mold on plants.
Damage Symptoms: When feeding on liriope and
mondo grass the scale causes yellow spots on the
foliage at the feeding sites.
Control: Pyriproxyfen (Distance) or buprofezin
(Talus) applied when crawlers appear or a soil
injection, basal flare, or soil drench application of
dinotefuran (Safari, Transtect).
Life Cycle: On liriope the scale has been observed
overwintering as late instar females in the crown of
the plants. Crawler emergence coincides with new
growth emerging form the liriope in May. A second
generation has been observed with crawlers present in
August and September. The second generation scale
appear to establish in the base of the mondo grass and
liriope plants.
Gloomy Scale (Melanaspis tenebricosa
(Comstock)), Family Diaspididae
APR
MAY
JUN
JUL
AUG SEP
OCT
Control: Cut off infested foliage in early spring
and remove it from the landscape. Treat with a
systemic insecticide or apply pyriproxyfen (Distance)
or buprofezin (Talus) and 0.5 – 1% oil when the
crawlers emerge in May.
Fletcher Scale (Parthenolecanium fletcheri
(Cockerell)), Family Coccidae
APR
MAY
JUN
JUL
AUG SEP
OCT
Plants Damaged: Arborvitae (Thuja species), and
yews (Taxus) are the two plants this soft scale is
commonly found on in Maryland. It has been reported
on pachysandra and juniper.
7
Plants Damaged: This armored scale is commonly
found on maples. It is also reported on several
woody plants including dogwood, sweet gum, poplar,
catalpa, black locust, willow, and grape.
Damage Symptoms: The heaviest damage is
reported on maples with dieback of terminal growth
on heavily infested trees.
Monitoring: Examine needles on the undersides for
the presence of this scale.
Control: Distance can be applied to the crawlers.
Horticultural oil can be used to control overwintering
females. Soil applications of dinotefuran (Safari,
Transtect) are effective in control of this scale.
Life Cycle: Fertilized females overwinter. Egg
laying occurs in early July and continues through
August. Crawlers are present a short time after egg
laying. Adult males are present in August.
Monitoring: Female covers are circular and brown
to gray in color. Shed skins in the center appear to be
shiny black.
Holly Pit Scale (Aterolecanium puteanum
Russell), Family Asterolecandidae
APR
MAY
JUN
JUL
AUG SEP
OCT
Control: A mixture of 0.5 - 1% horticultural oil and
pyriproxyfen (Distance) or buprofezin (Talus) could
be used on small trees. Dinotefuran (Safari, Transtect)
applied as a soil drench may control this pest.
Elongate Hemlock Scale (Fiorinia externa
Ferris), Family Diaspididae
APR
MAY
JUN
JUL
AUG SEP
OCT
Plants Damaged: American holly, Burford holly,
and Japanese holly. Most of the infestations have
been found on holly growing on the Eastern shore of
Maryland.
Damage Symptoms: Pitting and distortion of woody
tissue on branches and trunk of the tree. Heavy
infestations cause dieback of the plant.
Plants Damaged: Hemlock is the predominant tree
we see this scale damaging n Maryland but it also
attacks spruce, pine and Taxus yew.
Life Cycle: Mature females overwinter in a pit.
The pit is caused by the feeding damage to the plant
tissue. Crawlers emerge over a long period of time
during the summer. Once nymphs have settled on a
place on the plant they do not move.
Damage Symptoms: This scale feeds on the
needles and leaves of infested plants. Feeding causes
chlorosis of foliage and needle drop and dieback of
the plant.
Monitoring: Examine twigs and trunk of tree for
pit-like depressions with a scale insect in the middle
of the pit.
Life Cycle: There are two generations per season of
hemlock elongate scale. Crawlers are active in May.
The nymphs settle on the foliage of the plant where
they spend their whole life cycle. The generations
overlap for this scale which makes it somewhat
challenging to control. Crawlers can be produced
throughout the summer and into the fall.
Control: A mixture of 0.5 - 1% horticultural oil and
pyriproxyfen (Distance) or buprofezin (Talus) applied
when crawlers are present.
Photo of holly pit scale by Mike Raupp,
University of Maryland
8
Indian Wax Scale (Ceroplastes ceriferus),
Family Coccidae
APR
MAY
JUN
JUL
AUG SEP
Japanese Maple Scale (Lopholeucaspis
japonica (Cockerell)), Family Diaspididae
APR
OCT
Plants Damaged: This soft scale feeds on Chinese
and Japanese hollies, azaleas, pyracantha, euonymus,
boxwood, flowering quince, camellia, pear, azalea,
persimmon, plum, barberry, and magnolia.
MAY
JUN
JUL
AUG SEP
OCT
Plants Damaged: Japanese maple scale is showing
up in more landscapes and nurseries now. Look for
it on Japanese maple, red maple, dogwood, lilac,
zelkova, yellowwood, pyracantha, privet, holly,
euonymus, redbud, stewartia, cherry, magnolia, Itea,
and styrax.
Damage Symptoms: This scale is large enough
that its mere appearance is aesthetically unpleasing.
Heavy populations can cause dieback of the infested
plant.
Damage Symptoms: This armored scale feeds
directly on plant cells, not in the phloem tissue
like soft scale insects. Heavy populations cause a
slow decline of the tree. If high populations have
resulted in dead branches on trees, prune these out
before crawler hatch to reduce the number of scales
potentially moving onto other branches and trees.
Life Cycle: Females overwinter and eggs are laid in
May in Maryland. Crawlers are active in early June.
When crawlers emerge they will be yellow to pink in
color and will excrete white wax that gives the scale a
“cameo” appearance.
Life Cycle: The life cycle is poorly understood.
The male and females overwinters as immatures and
mature in early spring. There are two generations
per year. The 2 generations overlap and crawlers are
present from May through October.
Monitoring: Look for the white to gray, narrow
oyster shell shaped female covers on twigs and main
branches. Use a hand lens to look for the light purple
crawlers. They should be out in late May or early
June. Activity peaks in June to early July, and then
we have a second crawler period in late July to mid
September
Monitoring: The adult females are red and covered
with bright white gummy wax. Look for the large,
very noticeable females overwintering on the stems.
Control: Horticultural oil does not work well on this
scale. Pyriproxyfen (Distance) or buprofezin (Talus)
applied when crawlers are present works well.
Another option is to use a soil injection, basal flare,
or soil drench of a systemic insecticide, dinotefuran
(Safari, Transtect).
9
Control: Applications of 0.5 - 1% horticultural oil
and pyriproxyfen (Distance) or buprofezin (Talus)
should be made when crawlers are detected. This
should have about 2 - 3 week residual activity. At
that time monitor your plants again to see if crawlers
are still active. The twice-stabbed lady bird beetle
provides some biological control of this scale.
Maskell Scale (Lepidosaphes pallida
(Maskell)), Family Diaspididae
APR
MAY
JUN
JUL
AUG SEP
OCT
Magnolia Scale (Neolecanium cornuparvum),
Family Coccidae
APR
MAY
JUN
JUL
AUG SEP
OCT
Plants Damaged: Arborvitae, junipers, Leyland
cypress, Chamaecyparis, Cryptomeria, spruce, yew.
Plants Damaged: This scale is found mainly on
Magnolia stellata, M. acuminata, M.quimquepeta,
and M. soulangeana. This scale has been reported on
M. grandiflora.
Damage Symptoms: Yellowing and browning of
foliage. Dieback of branches.
Life Cycle: The exact number of generations per
year is not clear. First instar crawlers emerge in
June, and there is a second generation in August. In
Maryland adult males and females are present in
September through October. Eggs, crawlers and adult
are all present in the early to mid fall.
Damage Symptoms: Large amounts of honeydew
are produced by this scale in late summer. Heavy
infestations cause dieback.
Life Cycle: Overwintering nymphs are oval shape,
dark slate gray with a reddish brown ridge on its
back. Overwintering nymphs are found on twigs.
Nymphs move to foliage to feed during the summer.
Adult females mature in August with crawlers present
in September. There is one generation per year.
Monitoring: Examine foliage for elongated covers
on the needles of infested plants.
Control: In the dormant season a 2 - 4% horticultural
oil can be applied to foliage and twigs. Apply
pyriproxyfen (Distance) or buprofezin (Talus) and 0.5
- 1% oil mixture when crawlers are present.
Monitoring: Examine twigs for nymphs in winter.
Look for honeydew and sooty mold on foliage in late
summer.
Nanokermes pubescens (gall-like scale),
Family Kermesidae
Control: Horticultural oil can be applied in March
to control overwintering nymphs. Pyriproxyfen
(Distance) or buprofezin (Talus) applied to crawlers
in October.
APR
MAY
JUN
JUL
AUG SEP
OCT
Plants Damaged: Oak
Photo by Brian Kunkel, University of Delaware,
Bugwood.org
Damage Symptoms: Heavy infestations cause twig
dieback.
10
Life Cycle: This scale overwinters as second instar
nymphs. When leaves open the scale moves to
the foliage to feed on the undersides of the leaves,
usually along the mid-rib veins. The eggs hatch into
crawlers in June.
Control: Horticultural oil applied at a 2- 4% rate can
be applied in March. Apply pyriproxyfen (Distance)
or buprofezin (Talus) and 0.5 - 1% oil when crawlers
emerge.
Obscure Scale (Melanaspis obscura), Family
Diaspididae
Monitoring: Examine small twigs in winter for the
presence of nymphs. They are generally found on
the petioles and midribs of the leaves. Overwintering
nymphs attack newly expanding leaves in April.
Control: Pyriproxyfen (Distance) or buprofezin
(Talus) can be applied to the crawlers. Horticultural
oil can be used to control overwintering females. Soil
applications of dinotefuran (Safari, Transtect) are
effective in control of this scale.
APR
MAY
JUN
JUL
AUG SEP
OCT
Minute Cypress Scale (Carulaspis minima)
Family Diaspididae
APR
MAY
JUN
JUL
AUG SEP
OCT
Plants Damaged: Obscure scale is an armored scale
found on many pin oaks in the landscape, but is also
found on a few other species of oak such as white
oak. It has been reported on grape, dogwood, walnut,
Prunus spp, pecan and hickory.
Damage Symptoms: Yellowing of foliage and
dieback.
Life Cycle: The obscure scale has one generation
per year in Maryland. Second instar male and females
overwinter and mature in spring in May. Eggs are
laid in late June and July. Crawlers are present from
July through early September. Stoetzel and Davidson
(1973) found that this scale on white oak was one
month behind its development on red oak.
Plants Damaged: Arborvitae, Chamaecyparis,
Cryptomeria, junipers, spruce.
Damage Symptoms: Yellowing of foliage and
dieback.
Monitoring: Adult female covers are circular and
gray to black in color. The scales are usually crowded
together and overlap each other on the branches and
sometimes in the trunks of trees.
Life Cycle: One generation per year. Fertilized
females overwinter and eggs hatch in May and
crawlers are present from May through early June.
Adult males and females are present in early July.
Monitoring: The scale are usually found on the leaf
scales of small branches where they feed on the sap
of the host plant. Minute cypress scale looks very
similar to the Juniper scale, but the crawler period is
two weeks later than Juniper scale.
Control: Use 0.5 – 1% horticultural oil or
pyriproxyfen (Distance) or buprofezin (Talus) at
crawler emergence. The crawlers should be active in
central Maryland by the end of June.
Photo: James Solomon, USDA Forest Service, Bugwood.org
11
Oystershell Scale (Lepidosaphes ulmi
(Linnaeus)), Family Diaspididae
APR
MAY
JUN
JUL
AUG SEP
OCT
Damage Symptoms: Yellowing of foliage and
dieback of branches. This scale often exists in low
levels on white pines but rarely reaches damaging
levels.
Life Cycle: This scale overwinters as females and
eggs. Crawlers are present in May. The second
generation occurs in mid summer with crawlers
present from July through August.
Plants Damaged: This scale is a general feeder
(polyphagous) and is reported on 85 host plants
in 33 families. We have observed it commonly on
Acer (maples), Amelanchier (serviceberry), Cercis
(redbud), Crataegus (hawthorn), Quercus (oak), and
Prunus spp., but is found on many additional species.
Damage Symptoms: Yellowing of foliage and
dieback of branches.
Monitoring: When Sargent crabapple is in full
bloom we can expect to see crawlers on pine needle
scale. The reddish nymphs hatch in May and there is
a second generation in July.
Life Cycle: There are univoltine and bivoltine forms
found in Maryland. Bivoltine forms have crawlers
present in April. Crawlers of the univoltine form are
present from May through June.
Control: Use 0.5 – 1% horticultural oil and
pyriproxyfen (Distance) or buprofezin (Talus) at
crawler emergence. Dinotefuran (Safari, Transtect) is
reported to control this scale.
Monitoring: The adult females of this armored scale
look like elongated oysters.
Pine Tortoise Scale (Toumeyella parvicornis),
Family Coccidae
APR
Control: Use 0.5 – 1% horticultural oil and
pyriproxyfen (Distance) or buprofezin (Talus) at
crawler emergence.
Pine Needle Scale (Chionaspis pinifoliae
(Fitch)), Family Diaspididae
APR
MAY
JUN
JUL
AUG SEP
OCT
Plants Damaged: Pine is the main host, but it has
been observed on Abies (Spruce), Pseudotsuga, and
Tsuga (hemlock).
12
MAY
JUN
JUL
AUG SEP
OCT
Plants Damaged: Scots pine and Virginia pine
are the two species most severely attacked by pine
tortoise scale, but red, white and loblolly, Austrian
pines are also affected.
and edible plums, peaches and pears. It will also feed
on cherry laurel, cotoneaster, pyracantha, rose, and
other plants in the rose family.
Damage Symptoms: It feeds on the twigs and
small branches and weakens the plant. Yellowing of
foliage and dieback of branches
Damage Symptoms: These insects also produce
honeydew, a substrate for the growth of a sooty mold
fungus that blackens affected plants. Yellowing of
foliage and dieback of branches.
Life Cycle: San Jose scale has three generations per
year. The 3rd generation crawlers are still active in
October. On apples the crawlers will move out onto
the fruit in the first crawler emergence in May and
during the second crawler emergence in July. The 3rd
generation crawlers tend to be found on the twigs and
branches and less on the fruit. On apples you will see
round red circles on the fruit.
Life Cycle: Pine tortoise scale insects overwinter
on host twigs as immature females. They are reddish
brown and slightly wrinkled, but shiny, when they
first begin to develop on the twigs. The females
resume growth in the spring, reaching maturity in
June. The, eggs are laid beneath the female’s body
(several hundred per female!) and the amber-colored
young scale crawlers begin to emerge in June or early
July.
Monitoring: This scale derives its name from the
characteristic appearance of the mature females. They
look like tiny tortoises up to 1/4 inch in diameter and
are most often found on 1- and 2-year-old shoots of
“hard” pines.
Monitoring: The female covers are light brown
and round with a raised center. Examine branches
and twigs for the presence of overwintering female
covers. Use a hand lens to examine foliage for
presence of bright yellow crawlers which emerge in
May and June.
Control: Target the crawler stage for the best control.
Apply 0.5 – 1% horticultural oil and pyriproxyfen
(Distance) or buprofezin (Talus).
Control: A soil injection, basal flare, or soil drench of
a systemic insecticide, dinotefuran (Safari, Transtect)
is effective or apply 0.5 – 1% horticultural oil and
pyriproxyfen (Distance) or buprofezin (Talus) when
crawlers are active in June.
Tuliptree Scale (Toumeyella liriodendri),
Family Coccidae
APR
MAY
JUN
JUL
AUG SEP
OCT
San Jose Scale (Quadraspidiotus
perniciosus), Family Diaspididae
APR MAY JUN JUL AUG SEP OCT
Plants Damaged: This native soft scale prefers
tuliptree and magnolia.
Plants Damaged: This armored scale can be found
on apples, crabapples, crabapples, and ornamental
13
Damage Symptoms: Dieback of twigs and
yellowing of foliage. Black sooty mold often grows
on the honeydew that this scale excretes.
Life Cycle: They overwinter as black immatures
and begin feeding around late April. The tuliptree
scale females swell up in August and produce copious
amounts of honeydew. The black crawlers emerge in
September to October.
Control: When crawlers are out, pyriproxyfen
(Distance) or buprofezin (Talus) mixed with 0.5 - 1%
horticultural oil gives excellent control.
Monitoring: Tuliptree scale tends to be found on
small branches, whereas the magnolia scale is more
commonly found on the main trunk.
White Peach Scale (Pseudaulacaspis
pentagona), Family Diaspididae
APR
MAY
JUN
JUL
AUG SEP
OCT
Control: When crawlers are out, pyriproxyfen
(Distance) or buprofezin (Talus) mixed with 0.5 - 1%
horticultural oil gives excellent control or use a soil
injection, basal flare, or soil drench of a systemic
insecticide, dinotefuran (Safari, Transtect).
Walnut Scale (Diaspidiotus juglansregiae),
Family Diaspididae
APR
MAY
JUN
JUL
AUG SEP
OCT
Plants Damaged: This scale is a general feeder and
can be found on several species of plants including
holly, privet, cherry laurel, skimmia, mulberry,
catalpa, and chinaberry.
Damage Symptoms: Dieback of twigs, yellowing of
foliage
Life Cycle: First generation crawlers appears about
2 weeks later than white prunicola scale. Crawlers
are out in mid-May to mid-June. Second generation
crawlers are out from mid-July to mid-August. The
third generation crawlers are out in September.
Plants Damaged: This armored scale is a general
feeder and has been reported on 40 genera of plants.
Walnut scale is reported to infest holly, maples, birch,
redbud, crabapple, pines, poplar, Prunus species,
black locust, mahonia, lilac, linden, elm, willow, and
arborvitae.
Monitoring: Male crawlers are white and female
crawlers are salmon colored.
Control: When crawlers are out, pyriproxyfen
(Distance) or buprofezin (Talus) mixed with 0.5 - 1%
horticultural oil gives excellent control.
Life Cycle: One generation per year on holly
in Maryland. Second instar males and females
overwinter. Females lay eggs in June. Most crawlers
are present in mid- to late-June. Though most
crawlers are settled by mid-July, Stoetzel reported
that she found crawlers present through September.
Second instars are present sometime in September
and these overwinter for the next generation.
14
White Prunicola Scale (Pseudaulacaspis
prunicola), Family Diaspididae
APR
MAY
JUN
JUL
AUG SEP
OCT
Second generation crawlers are out from mid-July to
mid-August. The third generation crawlers are out in
September.
Monitoring: Both male and female crawlers are
salmon colored.
Control: When crawlers are out, pyriproxyfen
(Distance) or buprofezin (Talus) mixed with 0.5 - 1%
horticultural oil gives excellent control.
Plants Damaged: This scale is commonly found on
Prunus species and also seen on magnolia, ligustrum,
rhododendron, forsythia, boxwood, and lilac.
Damage Symptoms: Dieback of twigs and
yellowing of foliage.
Life Cycle: Crawlers are present in May. A second
generation occurs in July and a third in September.
Crawlers appear about 2 weeks earlier than white
peach scale. Crawlers are out in early May to June.
Scale Commonly Encountered in Maryland Landscapes and Nurseries
by
Stanton Gill, Extension Specialist, IPM for Nurseries and Greenhouse, Central Maryland
Research and Education Center, University of Maryland Extension, Ellicott City, MD, sgill@umd.edu
Shannon Wadkins and Suzanne Klick, Technicians, Central Maryland
Research and Education Center, University of Maryland Extension, Ellicott City, MD
The information given herein is supplied with the understanding that no discrimination is intended
and no endorsement by University of Maryland Extension is implied.
Read labels carefully before applying any pesticides.
Photographs are by Suzanne Klick and Stanton Gill unless stated otherwise.
University of Maryland Extension programs are open to all citizens without regard to race, color, gender,
disability, religion, age, sexual orientation, marital or parental status, or national origin.
Revised May 2015