This document provides information on identifying and managing scale insects that can infest trees, shrubs, and other perennials. It describes the different types of scales (armored scales, soft scales, and others), their life cycles, damage they cause, and management strategies. Effective management of scales relies primarily on conservation of natural enemies through practices like controlling tending ants, providing habitat and food sources for beneficial insects, and minimizing broad pesticide use.

1. SCALES
Integrated Pest Management for Home Gardeners and Landscape Professionals
Scale insects can be serious pests on
trees, shrubs, and other perennials.
The impact of infestations depends
on the scale species, the plant species
and cultivar, environmental factors,
and natural enemies. Populations of
some scales can increase dramatically
within a few months, such as when
honeydew-seeking ants or dusty
conditions interfere with scale natural
enemies. Plants are not harmed by a
few scales, and even high populations
of certain species apparently do not
damage plants. Soft scales and some
other species excrete honeydew, a sweet,
sticky liquid produced by insects that
ingest large quantities of plant sap.
Sticky honeydew and the blackish sooty
mold growing on honeydew can bother
people even when scale populations are
not harming plants.
IDENTIFICATION
Scales are unusual looking and many
people do not at first recognize them as
insects. Adult female scales and most
immatures (nymphs) are immobile,
wingless, and lack a separate head
or other recognizable body parts.
Immature scales and adult females
have a characteristic round or oval
to elongate and flattened or humped
appearance. Immature males are often a
different color and shape than females,
especially in later nymphal stages
(instars). Adult male scales are tiny,
delicate insects with one pair of wings.
Adult males are rarely seen, do not feed,
and live only a few hours.
Scales insert a tiny strawlike mouthpart
into plants and suck fluids. Scales can
occur on bark, fruit, or leaves. Armored
scales and soft scales are the most
common groups (families). Common
species of scales and their tree and
shrub hosts are listed in Tables 1–3.
Excellent color keys for scale insects
in California are available from the
California Department of Food and
Agriculture; see References for titles.
It is important to correctly distinguish
the scale family to which your pest
species belongs. For example, a popular
systemic insecticide (imidacloprid,
discussed below) controls European
elm scale and most soft scales but
does not control armored scales or
cottony cushion scale. Imidacloprid
can dramatically increase cottony
cushion scale populations because it is
very toxic to one of its natural enemies,
the vedalia beetle, Rodolia cardinalis.
This important cottony cushion scale
predator is poisoned by feeding on
scales that have ingested the insecticide.
Armored Scales. Armored scales,
family Diaspididae, have a flattened,
platelike cover that is less than 1/8 inch
in diameter. The actual insect body
is underneath the cover. The covers
often have a differently colored, slight
protuberance (exuviae, or “nipple”).
Concentric rings form as each nymphal
stage (instar) secretes an enlargement
to its cover (Fig. 1). Armored scales
do not excrete honeydew. Damaging
species include California red scale,
euonymus scale, oystershell scale, and
San Jose scale.
Soft Scales. Soft scales, family Coccidae,
can be smooth, cottony, or waxy and
are 1⁄4 inch long or less. They are
usually larger and more rounded and
convex than armored scales. Their
surface is the actual body wall of the
insect and cannot be removed. Soft
Figure 1. Armored scale infestation
on twig.
scales feed in the fluid-conducting
phloem tissue of the plant and excrete
abundant honeydew, which is sugary
water that drips from their bodies. Soft
scales include black scale, brown soft
scale, European fruit lecanium scale,
and various Pulvinaria species.
Other Species of Scale. Species
in other insect families include
cottony cushion scale and sycamore
scale (the woolly sac scales, family
Margarodidae), European elm scale
(felt scales, Eriococcidae), and oak pit
scales (Asterolecaniidae).
Scale Look-Alikes. Various other
organisms may be confused with scales.
These include California laurel aphid
(Euthoracaphis umbellulariae), coconut
mealybug (Nipaecoccus nipae), cypress
bark mealybug (Ehrhornia cupressi),
parasitized whitefly nymphs, and
psyllids such as lemongum lerp psyllid
(Cryptoneossa triangula) and redgum
lerp psyllid (Glycaspis brimblecombei).
Diamond “scale” infesting palms
is actually the fruiting bodies of
Sphaerodothis neowashingtoniae, an
Ascomycetes fungus!
PEST NOTES Publication 7408
University of California
Agriculture and Natural Resources
revised March 2007

2. March 2007 Scales
◆ 2 of 8 ◆
LIFE CYCLE
Females of many scale species
reproduce without mating (there are
no males). At maturity, adult females
produce eggs that are usually hidden
under her body or cover. Eggs hatch
into tiny crawlers (mobile first-instar
nymphs), which are yellow to orangish
in most species. Crawlers walk over
the plant surface, are blown by wind
to other plants, or can be inadvertently
moved by people or birds. They settle
down and begin feeding within a day
or two after emergence.
Settled nymphs may spend their entire
life in the same spot without moving
as they mature into adults. Nymphs
of other species can move slowly
but rarely do, such as when species
that feed on deciduous hosts move
from foliage to bark in the fall before
leaves drop. For species with multiple
generations, all scale life stages may
be present throughout the year in
areas with mild winters. Life cycles
and stages for scales are illustrated in
Figures 2 and 3.
Armored Scales. Most armored scales
have several generations a year.
Armored scales overwinter primarily as
first-instar nymphs and adult females.
Except for crawlers and adult males,
armored scales spend their entire
life feeding at the same spot. Settled
armored scales lose their legs, molt, and
form their characteristic covers, which
they gradually enlarge as they grow.
Soft Scales. Most soft scales have one
generation each year and overwinter
as second-instar nymphs. The multi-generational
brown soft scale is an
important exception Brown soft scale
females and nymphs of various size
can be present throughout the year.
Most immature soft scales retain
their barely visible legs and antennae
after settling and are able to move,
although slowly. At maturity, females
of certain soft scales, the woolly sac
scales (Margarodidae), and some
other species produce distinct external
cottony or wax-covered egg masses.
DAMAGE
When plants are heavily infested
with scales, leaves may look wilted,
turn yellow, and drop prematurely.
Scales sometimes curl leaves or cause
deformed blemishes or discolored
halos in fruit, leaves, or twigs. Bark
infested with armored scales may
crack and exude gum. Certain armored
scales also feed on fruit, but this
damage is often just aesthetic. Soft
scales infest leaves and twigs but rarely
feed on fruit. A major concern with soft
scales is their excretion of abundant
honeydew, which contaminates fruit,
leaves, and surfaces beneath plants.
Honeydew encourages the growth
of black sooty mold and attracts ants,
which in turn protect scales from
natural enemies.
When numerous, some scale species
weaken plants and cause them to
grow slowly. Branches or other plant
parts may die if they remain heavily
infested with scales. If plant parts die
quickly, dead brownish leaves may
remain on branches, giving them a
scorched appearance. Several years
of severe infestations may kill young
plants. Certain armored scales may be
more likely to kill plants. Soft scales
reduce plant vigor, but seldom kill trees
or shrubs.
MANAGEMENT
Scales are often well controlled by
beneficial predators and parasites,
except when these natural enemies are
disrupted by ants, dust, or application of
persistent broad-spectrum insecticides.
Preserving (conserving) the populations
of parasites and predators (such as by
controlling pest-tending ants) may be
enough to bring about gradual control
of scales as natural enemies become
more abundant. If scales become too
numerous, a well-timed and thorough
spray using horticultural (narrow-range)
oil applied either during the dormant
season or soon after scale crawlers are
active in late winter to early summer
should provide good control. Complete
spray coverage of infested plants (such
as the underside of leaves) is needed to
obtain good control. Thorough spray
coverage is especially critical when
treating armored scales and oak pit
scales, as these scales are generally less
susceptible to pesticides than soft scales.
crawler white cap
nipple stage
second-instar
female
second-instar
male
virgin female
adult
third- and fourth-instar
male (underside)
gravid female
(underside)
male adult
first instar
Figure 2. Life stages of a typical armored scale, the California red scale.

3. March 2007 Scales
crawlers
◆ 3 of 8 ◆
mature females
second instars on twig
females before
egg laying
eggs
beneath
female scale
Monitoring
Inspect plants to determine whether
female scales, nymphs, honeydew, or
sooty mold are present. When assessing
whether scales or their damage are
abundant enough to prompt you to
manage them, distinguish live scales
from dead or parasitized ones by
flipping over the female scale body
or cover using a sharp tool. The dead
scales from previous generations can
remain on plants, and sometimes a
large proportion of scales are dead or
parasitized by natural enemies. During
the growing season, inspect trunks
for ants. If the descending ants have
swollen, almost translucent abdomens,
they are probably feeding on honeydew
produced by scales or other insects that
suck plant juices. Tracing back trail-making
ants can lead you to colonies of
the honeydew-producing insects.
Action thresholds before spraying
have not been established for scales
in most situations. Monitor and
record scale densities and use the
density that caused damage (dieback
or unacceptable honeydew) as your
preliminary control action threshold.
Refine this threshold over time for your
local situation as you gain experience.
Tape traps for crawlers discussed in the
Foliage Sprays section and honeydew
monitoring are useful in certain
situations. Honeydew dropping from
plants can be efficiently monitored
using water-sensitive paper, which
is commonly used for monitoring
insecticide droplets and calibrating
sprayers. Products include bright
yellow cards that produce distinct blue
dots upon contact with honeydew or
water. Regularly monitoring honeydew
beneath plants (such as the number
of drops during four hours, once a
week) can help to develop thresholds
and evaluate effectiveness of the
treatment. Honeydew monitoring is
useful where there is a low tolerance for
dripping honeydew, when managing
many trees (such as along city streets
or in parks), and on tall trees where
the honeydew-producing insects may
be located too high to easily observe.
For more information on monitoring
honeydew, see the Aphids section in
Pests of Landscape Trees and Shrubs listed
in References.
Cultural Control
Provide plants with good growing
conditions and proper cultural care;
especially appropriate irrigation, so
they are more resistant to scale damage.
Prune off heavily infested twigs and
branches to eliminate scales when
infestations are on limited parts of the
plant. Pruning to open up tree canopies
helps to control black scale, citricola
scale, and possibly other species in
areas with hot summers, such as the
Central Valley of California. This
pruning increases scale mortality as a
result of heat exposure.
When landscaping, choose plants
that are relatively pest-free and well
adapted to local conditions. Consider
replacing problem prone plants. Most
pests are highly host specific. Scales
that can feed on many different plants
usually damage only certain of these
plant species and though present, do
not damage other species or cultivars
in the same plant genus. Notable
exceptions include California red scale
(which can severely infest and damage
all Citrus species) and San Jose scale
(which damages many different fruit
and nut trees).
Biological Control
Scales are often controlled by small
parasitic wasps and predators including
beetles, bugs, lacewings, and mites.
Predatory Chilocorus, Hyperaspis,
and Rhyzobius species lady beetles
(ladybugs) can easily be overlooked
because many are tiny, colored and
shaped like scales, or feed beneath
scales. Hyperaspis species are tiny, shiny,
black lady beetles with several red,
orange, or yellow spots on the back.
Rhyzobius lophanthae has a reddish head
and underside, and a grayish back
densely covered with tiny hairs. The
twicestabbed lady beetle, Chilocorus
orbus, is shiny black with two red spots
on its back, and reddish underneath.
The multicolored Asian lady beetle,
Harmonia axyridis, is a relatively
large, variably colored species. It is
mostly orange, red, or yellow with
19 large dark spots, or fewer, smaller,
or no spots on its wing covers. The
alligatorlike larvae of lady beetles
often occur openly on plants. In certain
species, small larvae are hidden under
the female scale body or cover where
they feed on scale eggs and crawlers.
Parasitic wasps are often the most
important natural enemies of scales
(Figure 4). Parasites include many
Figure 3. Life cycle of a typical soft scale insect (family Coccidae).
settled
first
instars
fall/winter
spring/summer

4. March 2007 Scales
Figure 4. Life cycle of a scale parasite. A. Female parasites
lay one or several eggs in or on each scale nymph.
B. Larvae emerge from the eggs and feed as immature
parasites shown here on a scale that is flipped upside down.
C. Parasites pupate and develop into adults. D. A roundish
hole in the dead scale is chewed by an emerging adult para-site.
◆ 4 of 8 ◆
species of Aphytis, Coccophagus, Encarsia,
and Metaphycus. The female wasp
lays one or several eggs in or on each
scale, where the tiny maggotlike wasp
larvae feed. When parasitized, some
scales are darker-colored than normal.
Estimate parasite activity before
making a treatment decision. Check
for discolored (parasitized) scales and
scale covers with round exit holes made
by emerging adult parasites. Lift the
covers of armored scales and examine
beneath them for immature parasites.
Natural enemies, or beneficial insects,
are commercially available for release
against California red scale and
perhaps certain other scales. However,
conserving resident natural enemies
is a more efficient and longer lasting
strategy than buying and releasing
beneficials in gardens and landscapes.
Ant control, habitat manipulation, and
pesticide management are the key
conservation strategies. Grow flowering
plants near scale-infested trees and
shrubs to help attract and support
natural enemies. Adults of predatory
bugs, lacewings, lady beetles, and
parasitic wasps live longer, lay more
eggs, and kill more scales when they
have plant nectar or pollen and insect
honeydew to feed on. Minimize dust,
which interferes with natural enemies.
For example, wash plant surfaces
midseason, or when the foliage is
covered with dust.
Depending on the scale species and
the extent to which biological control
has been disrupted, it will take several
months of conservation efforts (such as
controlling ants and dust and avoiding
application of persistent insecticides),
or until the next season or longer,
before scale populations are reduced
by biological control. If current levels
of scales are intolerable, use a short
residual insecticide such as oil or soap
to reduce scale populations while
conserving natural enemies.
Ant Control
Control ants if large
numbers of them are
climbing up trunks
to tend scales. Deny
ants access to plant
canopies by pruning
branches or weeds
that provide a bridge
between buildings
or the ground and
by applying a sticky
material (such as
Tanglefoot) to trunks.
Wrap the trunk with
a collar of fabric tree
wrap, heavy paper,
or masking tape to
avoid injury to bark;
wedge pliable wrap
snugly into cracks and
crevices; and coat the
wrap with the sticky
material. A barrier
band about 2 to 6
inches wide should
be adequate in most
situations. Increase the
longevity of the sticky
material by applying
it higher above the
ground to reduce
contamination by debris and sprinkler
wash-off.
F. The female wasp seeks scale nymphs to parasitize.
before they die, workers will spread
the toxicant among many other ants
during food sharing. Boric acid,
fipronil, and hydramethylnon are
examples of insecticides used in ant
baits. Although baits act slowly over
a period of hours to weeks (requiring
users to be patient), baits can be much
more effective than sprays. Sprays only
kill foraging workers, while ant baits
are carried back to their nests, where
reproductive queens and the entire
colony underground can be killed. See
Pest Notes: Ants in References for more
information.
Chemical Control of Scales
Horticultural oil (where plants can
be sprayed) and certain systemic
insecticides are preferred chemicals
for most situations when scales are
Do not wrap trunks too tightly. Inspect
wraps at least several times a year for
damage to bark, such as constricted
growth or injured tissue. Remove and
relocate any wrap at least once a year
to minimize bark injury. Check sticky
material at least every 1 to 2 weeks;
stir it with a stick to prevent ants from
crossing on collected debris. Avoid
applying sticky material to horizontal
surfaces where birds may roost.
Alternatively, or as a supplement, place
enclosed pesticide baits (insecticide
mixed with an attractant) such
as ant stakes near nests or on ant
trails beneath plants. Effective bait
insecticides are slow-acting, so that

5. March 2007 Scales
◆ 5 of 8 ◆
numerous enough to cause damage.
Dormant Season Sprays. Dormant
season application of a narrow-range
or horticultural oil is effective against
most scale pests on deciduous woody
plants. A good time to apply oil is when
no rain or fog is expected within a day.
On leafless host plants, application
can be made any time when weather
is suitable during dormancy to control
lecanium scales, San Jose scale, walnut
scale, and many other species. For oak
pit and sycamore scales, spray during
the delayed-dormant period, which is
after the buds swell but before buds
open. Do not spray oystershell or olive
scales during the dormant season
because susceptible stages of these
pests are not present during winter.
Oil Use and Precautions. Horticultural
oils are specially refined petroleum
products, often called narrow-range,
superior, or supreme oils. Some
botanical (plant-derived) oils are also
available. Thoroughly spraying plants
at the proper time with oil alone
usually provides adequate control. One
study of sycamore scale found that
organophosphates (e.g., malathion) or
organophosphates combined with oil
were no more effective than a thorough
spray of oil or insecticidal soap alone,
if properly timed during the delayed-dormant
period. Another study of
citricola scale on hackberry found
spraying oil on foliage once during late
spring after most crawlers emerged
was as effective as using a systemic
organophosphate (acephate).
Avoid products called dormant oil or
dormant oil emulsions. These are more
likely to injure plants. Do not apply oil
when it is foggy, freezing (under 32°F),
hot (over 90°F), or rainy, or within a day
of when these conditions are expected.
If leaves are present, to avoid oil injury,
be sure only to apply to well watered
plants. Do not apply horticultural oil to
deciduous trees within 30 days before or
after application of captan, sulfur, or certain
other fungicides to avoid damage to trees.
TABLE 1. Some Common Armored Scales (Diaspididae), Their Impact in California, and the Principal Hosts.
Common Name (Scientific Name) Susceptible Hosts and Impact Hosts Usually Not Damaged
California red scale (Aonidiella aurantii) citrus highly susceptible in Central
Valley; biologically controlled in
Southern California
acacia, boxwood, eugenia, euonymus, grape,
magnolia, mulberry, olive, palm, podocarpus,
privet, rose
cycad scale (Furchadaspis zamiae) cycads (sago palm) severely infested bird-of-paradise
euonymus scale (Unaspis euonymi) Euonymus japonica highly
susceptible
Euonymus kiautschovica (=E. sieboldiana)
tolerant, E. alata unaffected
greedy scale (Hemiberlesia rapax) generally not damaging acacia, bay, boxwood, ceanothus, cactus, fruit
trees, holly, ivy, laurel, magnolia, manzanita, palm,
pepper tree, pittosporum, pyracantha, redbud,
strawberry tree, willow
latania scale (Hemiberlesia lataniae) generally not damaging, except on
kiwifruit
acacia, avocado, Cedrus, English ivy, euonymus,
Fatsia, fuchsia, gladiolus, grevillea, Kentia,
philodendron, rose, Rubus, Salix, yucca
minute cypress scale (Carulaspis minima) Cupressus sempervirens highly
susceptible
arborvitae, cypress, juniper
obscure scale (Melanaspis obscura) biologically controlled chestnut, oaks, pecan
oleander scale (Aspidiotus nerii) generally not damaging acacia, aucuba, bay, boxwood, cactus, holly, ivy,
laurel, magnolia, manzanita, maple, mulberry,
oleander, olive, palm, pepper tree, redbud, sago
palm or cycad, Taxus (yew), yucca
olive scale (Parlatoria oleae) biologically controlled olive
oystershell scale (Lepidosaphes ulmi) poplars and willows especially
susceptible
alder, aspen, box elder, boxwood, ceanothus,
cottonwood, most deciduous fruit and nuts, holly,
maple, sycamore
purple scale (Lepidosaphes beckii) biologically controlled citrus
San Jose scale (Quadraspidiotus
nut and stone fruit trees can be
perniciosus)
highly susceptible
acacia, aspen, citrus, cottonwood, most maple,
mulberry, poplar, pyracantha, rose, strawberry
tree, willow
walnut scale (Quadraspidiotus juglansregiae) biologically controlled walnut
“Biologically controlled” species are usually not damaging, but can become pests if their natural enemies are disrupted by ants, dust, or
application of persistant broad-spectrum insecticides.

6. March 2007 Scales
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Foliage Sprays. Horticultural oil is
effective in spring or summer on
deciduous plants when sprayed soon
after most crawlers have emerged. Late
spring and summer are also the times
to spray avocado, citrus, and many
other broadleaf evergreens. Foliage-season
application requires more spray
volume on deciduous plants than a
dormant treatment because leaves
as well as bark must be thoroughly
covered. Spring or summer sprays
should thoroughly cover plant parts
where most scales occur (typically
twigs and the underside of leaves)
and be well timed to occur when most
scales are crawlers or young nymphs,
the most susceptible stages.
To effectively time a spray of leafy
plants, use traps made of double-sided
sticky tape to determine when crawlers
are hatching. Before crawlers begin
to emerge in spring, tightly encircle
several infested twigs or branches
with transparent tape that is sticky
on both sides (this tape is available
at stationery stores). Change the
tapes approximately once a week and
examine the tapes with a hand lens
to identify the crawlers. Once scale
eggs begin hatching, scale crawlers
get stuck on the tapes and appear as
yellow or orange specks. Spray after
crawler production has peaked and
the number trapped each week has
definitely declined, which is soon after
most crawlers have settled. For more
information on sticky tape monitoring,
consult Pests of Landscape Trees and
Shrubs, listed in References.
In addition to narrow-range oil,
insecticidal soap or a mixture of oil
and soap can be sprayed. Carbamate
insecticides (carbaryl or Sevin),
organophosphates (e.g., malathion),
and pyrethroids (e.g., bifenthrin
and cyfluthrin) are other contact
insecticides registered for scale control.
However, these more persistent
insecticides cause greater disruption
of biological control than oil or soap
because persistent residues continue to
kill or intoxicate beneficial insects and
mites migrating in after the application.
It is also best to avoid the more
persistent sprays because of problems
from their runoff into urban surface
water and contaminating municipal
wastewater.
Systemic Insecticides. Systemic
insecticides are absorbed and moved
within plants. If the plant is infested
with a scale species susceptible to
systemic insecticide, systemics are
particularly useful where it is not
practical to spray because plants are
large or spray may drift to unintended
areas. Depending on the product,
systemic insecticide may be applied
by spraying foliage, injection or
implantation into trunk vascular tissue,
or applying on or into soil beneath
trees and shrubs, where the insecticide
is absorbed by roots.
A soil application of the systemic
insecticide imidacloprid can provide
season-long control of soft scales
and certain other species such as
European elm scale. Imidacloprid is
not effective on armored scales and
certain other species such as cottony
cushion scale. Imidacloprid is available
to both homeowners (Bayer Advanced
Garden Tree & Shrub Insect Control)
and professional applicators (Merit and
others). Imidacloprid can be effective
when applied to soil during late winter
to early spring or before rainfall or
irrigation are expected to facilitate root
Figure 5. When applying systemic pesticides to trees, make an application to soil whenever possible as directed on product
labels instead of injecting or implanting trunks with pesticides. Injecting or implanting trunks injures trees and can introduce
or facilitate entry of plant pathogens.

7. March 2007 Scales
TABLE 2. Some Common Soft Scales (Coccidae), Their Impact in California, and the Principal Hosts.
Common Name (Scientific Name) Susceptible Hosts and Impact Hosts Usually Not Damaged
black scale (Saissetia oleae) sometimes annoyingly abundant
away from the coast and if ant-tended
◆ 7 of 8 ◆
aspen, bay, citrus, cottonwood, coyote bush, holly,
maple, mayten, oleander, olive, palm, pear, pepper
tree, pistachio, poplar, privet, stone fruit, strawberry
tree, walnut
brown soft scale (Coccus hesperidum) annoyingly abundant if ant-tended aspen, avocado, citrus, cottonwood, holly, manzanita,
palm, poplar, stone fruit, strawberry tree, willow
calico scale (Eulecanium cerasorum) liquidambar sometimes damaged box elder, maple, stone fruit, walnut
citricola scale (Coccus
pseudomagnoliarum)
citrus and hackberry sometimes
damaged in Central Valley;
biologically controlled in Southern
California
elm, pomegranate, walnut
European fruit lecanium, also called
brown apricot scale (Parthenolecanium
corni)
annoying abundant sometimes alder, almond, aspen, cottonwood, elm, grape, pear,
pistachio, poplar, stone fruit, toyon, walnut
frosted scale (Parthenolecanium
pruinosum)
walnut sometimes damaged ash, birch, elm, laurel, locust, pistachio, rose,
sycamore
green shield scale (Pulvinaria psidii) all plants with this scale are
quarantined, under eradication or
regulatory control
aralia, begonia, camellia, croton, eugenia, gardenia,
hibiscus, laurel fig or Indian laurel (Ficus retusa),
pepper tree, pittosporum, plumeria, Schefflera
irregular pine scale (Toumeyella pinicola) Monterey pine infested, mostly in
Bay Area
other pines
Kuno scale (Eulecanium kunoense) stone fruit sometimes damaged,
especially plum
cotoneaster, pyracantha, rose, walnut
tuliptree scale (Toumeyella liriodendri) deciduous magnolias and tuliptree
(yellow poplar) highly susceptible
gardenia, linden
wax scales, including barnacle and
Chinese wax scales (Ceroplastes spp.)
annoyingly abundant sometimes
on Escallonia, gardenia, Geijera
parviflora, and mayten
California bay laurel, citrus, coyote bush, holly,
Mahonia, pepper tree
TABLE 3. Some Common Scales in Other Families, Their Importance in California, and the Principal Hosts.
Common Name (Scientific Name) Susceptible Hosts and Impact Hosts Usually Not Damaged
cottony cushion scale1 (Icerya purchasi, family
Margarodidae)
Cocculus laurifolius highly
susceptible, biologically controlled
on other hosts
citrus, nandina, pittosporum2
European elm scale (Gossyparia spuria, Eriococcidae) American and Chinese elms
especially susceptible
other elms
oak pit scales3 (Asterolecanium spp., Asterolecaniidae) Quercus lobata, Q. douglasii, and
Q. rober highly susceptible
other oaks
sycamore scale4 (Stomacoccus platani, family
Margarodidae)
London plane and sycamore
susceptible
—
1 See Pest Notes: Cottony Cushion Scale, UC ANR Publication 7410
2 Cottony cushion scale can harm “Hosts Usually Not Damaged” if natural enemies are disrupted, such as by application of certain
persistent insecticides.
3 See Pest Notes: Oak Pit Scales, UC ANR Publication 7470
4 See Pest Notes: Sycamore Scale, UC ANR Publication 7409

8. March 2007 Scales
WARNING ON THE USE OF CHEMICALS
Pesticides are poisonous. Always read and carefully follow all precautions and safety recommendations
given on the container label. Store all chemicals in the original labeled containers in a locked cabinet or shed,
away from food or feeds, and out of the reach of children, unauthorized persons, pets, and livestock.
Pesticides applied in your home and landscape can move and contaminate creeks, lakes, and rivers.
Confine chemicals to the property being treated. Avoid drift onto neighboring properties, especially gardens
containing fruits or vegetables ready to be picked.
Do not place containers containing pesticide in the trash or pour pesticides down sink or toilet. Either use
the pesticide according to the label or take unwanted pesticides to a Household Hazardous Waste Collection
site. Contact your county agricultural commissioner for additional information on safe container disposal and
for the location of the Household Hazardous Waste Collection site nearest you. Dispose of empty containers
by following label directions. Never reuse or burn the containers or dispose of them in such a manner that
they may contaminate water supplies or natural waterways.
The University of California prohibits discrimination or harassment of any person on the basis of race,
color, national origin, religion, sex, gender identity, pregnancy (including childbirth, and medical condi-tions
related to pregnancy or childbirth), physical or mental disability, medical condition (cancer-related
or genetic characteristics), ancestry, marital status, age, sexual orientation, citizenship, or status as a
covered veteran (covered veterans are special disabled veterans, recently separated veterans, Vietnam
era veterans, or any other veterans who served on active duty during a war or in a campaign or expedi-tion
for which a campaign badge has been authorized) in any of its programs or activities. University
policy is intended to be consistent with the provisions of applicable State and Federal laws. Inquiries
regarding the University’s nondiscrimination policies may be directed to the Affirmative Action/Staff
Personnel Services Director, University of California, Agriculture and Natural Resources, 300 Lakeside
Drive, 6th Floor, Oakland, CA 94612-3550, (510) 987-0096.
◆ 8 of 8 ◆
For more information contact the University
of California Cooperative Extension in your county.
See your telephone directory for addresses and
phone numbers.
AUTHORS: S. H. Dreistadt, UC Statewide IPM
Program, Davis; J. G. Morse, Entomology, UC Riv-erside;
P. A. Phillips, UC Statewide IPM Program,
Ventura Co.; R. E. Rice, Entomology, emeritus,
Kearney Agricultural Center, Parlier
TECHNICAL EDITOR: M. L. Flint
COORDINATION & PRODUCTION: P. N. Galin
ILLUSTRATIONS: Fig. 1: V. Winemiller; Fig. 2: D.
Kidd; Fig. 3: S. H. Dreistadt; Fig. 4: adapted from
H. J. Quayle. 1938. Insects of Citrus and other
Subtropical Fruits. Ithaca, NY: Comstock; Fig. 5:
adapted from S. H., Dreistadt, J. K. Clark, and
M. L. Flint. 2004. Pests of Landscape Trees and
Shrubs: An Integrated Pest Management Guide.
UC Statewide IPM Program. Oakland: Univ. Calif.
Agric. Nat. Res. Publ. 3359
Produced by IPM Education & Publications,
UC Statewide IPM Program, University of
California, Davis, CA 95616-8620
This Pest Note is available on the
World Wide Web (www.ipm.ucdavis.edu)
This publication has been anonymously peer
reviewed for technical accuracy by University of Cali-fornia
scientists and other qualified professionals. This
review process was managed by the ANR Associate
Editor for Pest Management.
To simplify information, trade names of products
have been used. No endorsement of named products
is intended, nor is criticism implied of similar products
that are not mentioned.
This material is partially based upon work supported by
the Extension Service, U.S. Department of Agriculture,
under special project Section 3(d), Integrated Pest
Management.
trunks (Figure 5). It is difficult to place
insecticide into trunks at the proper
depth. Also, unsterilized injection tools
contacting internal parts of multiple
plants may mechanically spread certain
plant pathogens, including bacteria
(e.g., slime flux or wetwood), fungi
(e.g., vascular wilt pathogens), and
viruses. The physical act of penetrating
trunks during injections injures plants.
Especially avoid methods that cause
large wounds, which may lead to wood
decay. Do not inject or implant trunks
more than once a year.
REFERENCES
Dreistadt, S. H., J. K. Clark, and M. L.
Flint. 2004. Pests of Landscape Trees and
Shrubs: An Integrated Pest Management
Guide, UC Statewide IPM Program.
Oakland: Univ. Calif. Agric. Nat. Res.
Publ. 3359.
Flint, M. L. 1998. Pests of the Garden
and Small Farm: A Grower’s Guide to
Using Less Pesticide. UC Statewide IPM
Program. Oakland: Univ. Calif. Agric.
Nat. Res. Publ. 3332.
Flint, M. L., and S. H. Dreistadt. 1998.
Natural Enemies Handbook: The Illustrated
Guide to Biological Pest Control. UC
Statewide IPM Program. Oakland:
Univ. Calif. Agric. Nat. Res. Publ. 3386.
Geisel, P., and E. Perry. 2004. Pest
Notes: Oak Pit Scales. UC Statewide IPM
Program. Oakland: Univ. Calif. Agric.
Nat. Res. Publ. 7470. Also available
online at www.ipm.ucdavis.edu.
Gill, R. J. 1982. Color-Photo and Host Keys
to the Armored Scales of California. Scale
and Whitefly Key #5. Sacramento: Calif.
Dept. Food Agric.
Gill, R. J. 1982. Color-Photo and Host Keys
to the Soft Scales of California. Scale and
Whitefly Key #4. Sacramento: Calif.
Dept. Food & Agric.
Gill, R. J. 1988-1997. The Scale Insects of
California Parts 1–3. Sacramento: Calif.
Dept. Food & Agric.
Grafton-Cardwell, E. E. 2003. Pest
Notes: Cottony Cushion Scale. UC
Statewide IPM Program. Oakland: Univ.
Calif. Agric. Nat. Res. Publ. 7410. Also
available online at www.ipm
.ucdavis.edu
Klotz, J., and M. Rust. 2005. Pest Notes:
Ants. UC Statewide IPM Program.
Oakland: Univ. Calif. Div. Agric. Nat.
Res. Publ. 7411. Also available online at
www.ipm.ucdavis.edu
UC Statewide IPM Project. 2000. Pest
Notes: Sycamore Scale. Oakland: Univ.
Calif. Agric. Nat. Res. Publ. 7409. Also
available online at www.ipm.ucdavis
.edu ❖
absorption of the insecticide. Summer
application to stressed, heavily infested
trees is less likely to be effective and is
not recommended.
Certain other systemic insecticides are
also available, but only to professional
applicators. For example, dinotefuran
(Safari) is a neonicotinoid (in the same
chemical group as imidacloprid) that
can be sprayed onto foliage or applied
onto soil or through certain irrigation
systems, especially to control cycad
scale and soft scales.
Injecting Trunks. When using systemics,
consider making a soil application
whenever possible instead of spraying
foliage or injecting or implanting