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Scale Commonly Encountered in Maryland Landscapes and Nurseries

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					                          Scale Commonly Encountered in Maryland Landscapes and Nurseries
                                          Stanton Gill, Extension Specialist in IPM for Nurseries and Greenhouses,
                                                  and Suzanne Klick and Shannon Wadkins, Technicians
                               Central Maryland Research and Education Center, University of Maryland Cooperative Extension


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 foliar chlorosis 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.

Azalea Bark Scale (Acanthococcus azaleae), Family Erioccicdae

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, and they hatch in central Maryland in late May to early
June. Individual crawlers are active 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 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 for control.
                                                                                                   APR MAY JUN               JUL   AUG SEP   OCT
Calico Scale (Eulecanium cerasorum), Family Coccidae

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.
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.
                                                                                                         APR MAY JUN JUL AUG SEP OCT
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 active, use 1% horticultural oil or Distance. Another option for controlling soft
scale is to use a soil injection or soil drench of a systemic insecticide, such as imidacloprid or dinotefuran. This material takes 30 - 60 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.

European Fruit Lecanium (Parthenolecanium corni), Family Coccidae

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
scale is a common soft scale 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.
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 growing on the honeydew excreted on the foliage and                APR MAY JUN           JUL     AUG SEP        OCT
branches. Inspect branches using a 10 -16X magnifier for crawlers
Control: Distance and 1% horticultural oil applied when crawlers are active gives good
control. Another option is soil applications of imidacloprid or dinotefuran as a soil drench.
Cottony Camellia/Taxus Scale (Pulvinaria floccifera), Family Coccidae

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 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.
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 the insect growth regulator Distance or oil.
Soil injections of imidacloprid (Merit in the landscape, Marathon in nurseries) can be applied in
April.
                                                                                                    APR MAY JUN     JUL   AUG SEP   OCT




Cottony Cushion Scale, (Icerya purchase Maskell), Family Margarodidae

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.
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 have had samples
from Prince George’s County and the District of Columbia 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.
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) should give good control. Another option is to apply Distance to mobile stages during the summer
months.
Biological Control: A ladybug called the Vedalia beetle, Rodolia cardinalis, has been used to
                                                                                                      APR MAY JUN   JUL   AUG SEP   OCT
control this scale.
Cryptomeria Scale (Aspidiotus cryptomeriae Kuwana), Family Diaspididae

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 yellow
spotting of the 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: Look for chlorotic foliage with yellow spotting or banding on the needles. Look
for overwintering scale on the needles.
Control: A mixture of 1% horticultural oil and Distance does a great job of controlling this
                                                                                                APR MAY JUN   JUL   AUG SEP   OCT
scale. Dinotefuran (Safari) applied as a soil drench also works well.




Euonymus Scale (Unaspis euonymi (Comstock), Family Diaspididae

Plants damaged: Boxwood, camellia, and evergreen euonymus – especially Euonymus
japonica.
Damage Symptoms: Yellowing of foliage, dieback of twigs, and general thinning of
infested plants.
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 Distance does a great job of controlling this
scale. Dinotefuran (Safari) applied as a soil drench also works well.


                                                                                                APR MAY JUN   JUL   AUG SEP   OCT
European Elm Scale (Gossparia spuria)
Family Coccidae

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 (photo on right) in bark cracks on elms.
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: Soil drench of dinotefuran (Safari) or imidacloprid (Merit in landscape, Marathon in the nursery). Applications of oil or Distance are not
practical on large trees.
                                                                                                 APR MAY JUN            JUL    AUG SEP        OCT



Winged Euonymus Scale (Lepidosaphes yanangicola
(Kuwana)), Family Diaspididae

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 branches 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.
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.                                                                                          APR MAY JUN            JUL    AUG SEP        OCT
Control: A mixture of 1% horticultural oil and Distance does a great job of controlling this
scale. Dinotefuran (Safari) applied as a soil drench also works well.
False Florida Red Scale (Chrysomphalus bifasciculatus (Ferris)), Family Diaspididae

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. The crawlers
move out onto the host foliage. It is not known if there is a second generation per season but you can
examine 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 this is just an occasional pest or a major threat to the health of the plant by the
population level and any dieback occurring. If control is necessary then a mixture of 1% horticultural oil and
Distance does a great job of controlling this scale. Dinotefuran (Safari) applied as a soil drench also works
well.



                                                                                                    APR MAY JUN   JUL   AUG SEP   OCT




Felt Scale (Eriococcus quercus)

Plants Damaged: Only recorded on oaks
Damage symptoms: Heavy populations can cause yellowing of foliage and slow decline of
trees.
Life Cycle: Life cycle is not well studied and recorded. It 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. Rarely found on leaves.
Monitoring: Examine the base of branches were populations tend to accumulate
Control: Distance or Talus applied at crawler period. Systemic neonectonoids applied as soil
drenches should provide control.



                                                                                                    APR MAY JUN   JUL   AUG SEP   OCT
Fern Scale (Pinnaspis aspidistrae (Signoret)), Family Diaspididae

Plants Damaged: In Maryland this scale is found mainly on liriope, Rhodea and mondo
(Ophiopgon) grass and ferns but it is a general feeder and has been reported on camellia,
persimmon, peony, and Prunus.
Damage Symptoms: When feeding on liriope and mondo grass the scale causes yellow spots on
the foliage at the feeding sites.
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 appear to establish in the base of the mondo grass and liriope plants.
Control: Cut off infested foliage in early spring and remove it from the landscape. Treat with a
systemic insecticide or apply Distance and oil when the crawlers emerge in May.



                                                                                                   APR MAY JUN   JUL   AUG SEP   OCT




Fletcher Scale (Parthenolecanium fletcheri (Cockerell)), Family Coccidae

Plants Damaged: Arborvitae (Thuja species), and yews (Taxus) are the two plants this soft
scale is commonly found on in Maryland. It has also been reported on pachysandra and juniper.
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 June- about the time when catalpa trees
bloom.
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.
Control: Distance applied when crawlers appear or a soil injection of imidacloprid (Merit) or
dinotefuran (Safari).


                                                                                                   APR MAY JUN   JUL   AUG SEP   OCT
Gloomy Scale (Melanaspis tenebricosa (Comstock)), Family Diaspididae

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.
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.
Control: A mixture of 1% horticultural oil and Distance could be used on small trees. Dinotefuran
(Safari) applied as a soil drench may control this pest.


                                                                                                    APR MAY JUN   JUL   AUG SEP   OCT




Elongate Hemlock Scale (Fiorinia externa Ferris), Family Diaspididae

Plants Damaged: Hemlock is the predominant tree we see this scale damaging in Maryland, but it
also attacks spruce, pine and yew.
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.
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.
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) are effective in control of this scale.



                                                                                                    APR MAY JUN   JUL   AUG SEP   OCT
Holly Pit Scale (Aterolecanium puteanum Russell), Family Asterolecandidae

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: This scale causes pitting and distortion of woody tissue on branches and
trunk of the tree. Heavy infestations cause dieback of the plant.
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.
Monitoring: Examine twigs and trunk of tree for pit-like depressions with a scale insect in the
middle of the pit.
Control: Horticultural oil or Distance and oil applied when crawlers are present.

Photo by Mike Raupp, University of Maryland

                                                                                                  APR MAY JUN      JUL   AUG SEP   OCT




Indian Wax Scale (Ceroplastes ceriferus), Family Coccidae

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.
Damage Symptoms: This scale is large enough that its mere appearance is aesthetically unpleasing.
Heavy populations can cause dieback of the infested plant.
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.
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. Distance applied when crawlers are present
works well. Imidacloprid can also be applied as a soil drench in April. It takes 30 - 60 days for uptake
into the stems of the plant. Soil application of dinotefuran (Safari) is uptaken in 2 – 3 weeks
and should give good control.                                                                        APR MAY JUN   JUL   AUG SEP   OCT
Japanese Maple Scale (Lopholeucaspis japonica (Cockerell)), Family Diaspididae

Plants Damaged: Japanese maple scale is showing up in more and more landscapes and nurseries
lately. Look for this scale on Japanese maple, American red maple, dogwood, zelkova, lilac,
yellowwood, pyracantha, privet, holly, euonymus, redbud, stewartia, cherry, magnolia, itea, and
styrax.
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: 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 two 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 in Maryland. Activity peaks in June to early July, and then we have a second crawler
period in late July to mid September
Control: Applications of 1% horticultural oil and Distance should be made when crawlers are       APR MAY JUN       JUL    AUG SEP           OCT
detected. This application should have about a 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.



Magnolia Scale (Neolecanium cornuparvum), Family Coccidae
                                                                                              APR MAY JUN           JUL    AUG SEP           OCT
Plants Damaged: This scale is found mainly on Magmolia stellata, M. acuminata,
M.quimquepeta, and M. soulangeana. This scale has been reported on M. grandiflora.
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 twigs for nymphs in winter. Look for honeydew and sooty mold on foliage in late summer.
Control: Horticultural oil can be applied in March to control overwintering nymphs. Distance (IGR) applied to crawlers in October.
Maskell Scale (Lepidosaphes pallida (Maskell)), Family Diaspididae

Plants Damaged: Arborvitae, junipers, Leyland cypress, Chamaecyparis, Cryptomeria, spruce, Taxus yew.
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 adults are all present in the early to mid fall.
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 Distance
and 1% oil mixture when crawlers are present.




                                                                                                   APR MAY JUN            JUL    AUG SEP         OCT




Nanokermes pubescens (gall-like scale), Family Kermesidae

Plants Damaged: Oak
Damage Symptoms: Heavy infestations cause twig dieback.
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.
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: Distance can be applied to the crawlers. Horticultural oil can be used to control overwintering females. Soil applications of dinotefuran
(Safari) are effective in control of this scale.
                                                                                                   APR MAY JUN            JUL    AUG SEP         OCT
Minute Cypress Scale (Carulaspis minima), Family Diaspididae

Plants Damaged: Arborvitae, Chamaecyparis, Cryptomeria, junipers, and spruce.
Damage Symptoms: Yellowing of foliage and dieback.
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: Horticultural oil applied at a 2- 4% rate can be applied in March. Apply Distance and 1% oil
when crawlers emerge.



                                                                                                     APR MAY JUN   JUL   AUG SEP   OCT




Obscure Scale (Melanaspis obscura), Family Diaspididae

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.
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.
Control: Horticultural oil or Distance at crawler emergence. The crawlers should be active
in central Maryland by the end of June.
Photo by James Solomon, USDA Forest Service, Bugwood.org
                                                                                                     APR MAY JUN   JUL   AUG SEP   OCT
Oystershell Scale (Lepidosaphes ulmi (Linnaeus)), Family Diaspididae

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.
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.
Monitoring: The adult females of this armored scale look like elongated oysters.
Control: Horticultural oil or Distance at crawler emergence.




                                                                                                   APR MAY JUN   JUL   AUG SEP   OCT




Pine Needle Scale (Chionaspis pinifoliae (Fitch)), Family Diaspididae

Plants Damaged: Pine is the main host, but it has been observed on Abies (Spruce), Pseudotsuga, and
Tsuga (hemlock).
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.
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.
Control: Horticultural oil or Distance at crawler emergence. Dinotefuran (Safari) is reported to control this
scale.




                                                                                                   APR MAY JUN   JUL   AUG SEP   OCT
Pine Tortoise Scale (Toumeyella parvicornis), Family Coccidae

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.
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: 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.
Control: Soil injections of imidacloprid are effective or apply horticultural oil and Distance      APR MAY JUN   JUL   AUG SEP   OCT
when crawlers are active in June.




San Jose Scale (Quadraspidiotus perniciosus), Family Diaspididae

Plants Damaged: This armored scale can be found on apples, crabapples, crabapples, and
ornamental 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
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.
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 Distance and 1 % horticultural oil.   APR MAY JUN   JUL   AUG SEP   OCT
Tuliptree Scale (Toumeyella liriodendri), Family Coccidae

Plants Damaged: This native soft scale prefers tuliptree and magnolia.
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.
Monitoring: Tuliptree scale tends to be found on small branches, whereas the magnolia
scale is more commonly found on the main trunk.
Control: When crawlers are out, Distance mixed with 1% horticultural oil gives excellent
control or use a systemic labeled for soft scale like Merit (imidacloprid) or Safari (dinotefuran).




                                                                                                      APR MAY JUN   JUL   AUG SEP   OCT




Walnut Scale (Diaspidiotus juglansregiae), Family Diaspididae

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.
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.
Control: When crawlers are out, Distance mixed with 1% horticultural oil gives excellent
control.



                                                                                                      APR MAY JUN   JUL   AUG SEP   OCT
White Peach Scale (Pseudaulacaspis pentagona), Family Diaspididae

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: 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.
Monitoring: Male crawlers are white and female crawlers are salmon colored.
Control: When crawlers are out, Distance mixed with 1% horticultural oil gives excellent control.




                                                                                                APR MAY JUN    JUL   AUG SEP   OCT



White Prunicola Scale (Pseudaulacaspis prunicola), Family Diaspididae

Plants Damaged: This scale is commonly found on Prunus species but can also be 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.
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, Distance mixed with 1% horticultural oil gives excellent control.



                                                                                                APR MAY JUN    JUL   AUG SEP   OCT




                         Photographs by Suzanne Klick, Stanton Gill and Shannon Wadkins unless otherwise noted.
                The information given herein is supplied with the understanding that no discrimination is intended and no
                                      endorsement by Maryland Cooperative Extension is implied.
                                                      Equal Opportunity Programs

				
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