Klingeman, W. E., P. Lambdin, and F. A. Hale. 2002.

and researchers. In this issue,we discuss
behavior,and introducea practicaltool
that can help landscapeand nursery I
second stage
(nymphs),andthe adult. In general,
adult female scales are wingless.
professionals manage scale and
Femalesmayproducefrom lessthan
mealybug
populations
before
a dozen, to over a thousand eggs
economicand aestheticinjury occur.
during her lifetime, depending on
Numerous native and ornamental
the species. As she depositseggs,
plants, whether in the landscape,
her body shrivels up to eventually
interiorscape, or production system,
occupy only the foremostone-third
have associated scale insect pests.
of the waxy covering (or "test"),
Unfortunately,becauseof their small
leaving the eggs protected from
size, cryptic features, and sedentary
environmental changes and many
behaviors,scalesoftengo unnoticedon
natural enemies. When males of a
Figure1. Differentappearancesof adultscaleinsects:
the leaflets or branchesuntil a heavy
species exist, they can look so
A.) Europeanfruitlecanium scale (Parthenolecanium
infestation is present making them
different from the adult female that
corm), B.) cottony camellia scale (Pulvarinia
more difficult to control.
pairing them as a species can be
floccifera), C.) obscure scale (Melanaspis obscura),
Scale insects belong to the Order
very difficult. Adult male scales
D.) euonymusscale (Unaspis euonym/),E.) tuliptree
Hemiptera, which now includes those
resemble aphids, but are easily
scale (Toumeyel/a liriodendrl), and F.) oystershell
speciesonceplaced in the Homoptera.
distinguished by having only one
scale (Lepidosaphesulm/). (Photosprovidedby F.H.,
Scaleinsectsdiffer from other species
pair of wings. Within a day or two
UT-EPp).
in both their development and
after hatching, crawlers migrate,
morphology. Over 7,000 species of
either by walking or wind, to new
scale insects, representing some 22 families, are known feeding sites on the host plant or adjacentplants. Once a
worldwide. Of these families, armored scales(Diaspididae), suitable site is located,crawlers settle, insert their needle-like
mealybugs (Pseudococcidae),soft scales (Coccidae),and pit mouthparts,begin to feed, and continueto mature. For many
scales (Asterolecaniidae),respectively, contain the greatest species, favorable environmental conditions will result in
Tennessee
Green
Times
Spring
2002
Because they are mobile,
severalgenerationsof scaleswithin one
crawlers are the life stage best
season.
Heavy infestationsof feedingscales suited to nursery and landscapemonitoring.
When an infested:
may result in loss of vigor, stunting,
dieback,or deathto the hostplant. While plant is located, double-sided!
feeding, scalesinjure plant surfacesby transparenttape canbe usedas a
piercing tissues with needle-like scoutingtool. In spring,prior to
mouthparts. This producesopenwounds crawleremergence
(Table I), tape
into which plant pathogens gain entry traps can be placed on small
into the plant. In someinstances,saliva stems or limbs beneath large
injectedinto plant tissuesduring feeding adultscales.Use one or two tape
may be toxic to the host plant. Such traps on smallshrubsandthree or
salivary injections can result in gall four traps, spaced at different
formation,
deformed areas, or heights and sides of larger trees.
discolorationaround the feeding site, as Try not to pressadjacentsidesof
well as leaf and bud abortion. The the tape together around the
Figure2. Sticky tape trap on a small stem. (Photo
primary injury to the host plant by scale branch. Instead,roll one side of
provided
by B.K., UT-PSLS).
insect feeding, however, occurs through the tape aroundthe stem for two
the extractionof huge quantities of sap. or threeturns onto itself-just the
Sap feeding, which also results in host reverseof the way it cameoff of
coloredcrawlersarecapturedon the tape.
plant dieback,defoliation, fruit damage, the roll (Figure2). This makesremoving High humidity and rainfall may make it
or death, is projected to produce annual the tape a relatively simple task and necessaryto replacethe sticky tape on a
crop lossesin excessof $500million.
minimizes steminjury. A smallpiece of weekly or biweekly basis. Sticky tape
Many soft scale insects and colored flagging ribbon can be used to trap counts can be recorded throughout
mealybug species,like aphids, exude a quickly relocate the tape within the the seasonto determinethe effectiveness
watery excretion that is a by-product of nurseryor landscape. Returnto observe of the controlprogram.
the large volumes of sapthat they ingest. the tape traps on at least two-week
Because they have not yet
Because scales are challenged to intervals, until the cream to orange completely developed their protective
inefficiently process sap, they exude a ~
waterysolution, called "honeydew",that:
is rich in plant sugars,amino acids,and
excesswater. Honeydew can typically
be found on leavesand branchesbelow
the pestsand servesasa substratefor the
development of sooty mold: a fungus
that produces dark fungal strands and
spores. Dark sooty mold on leaves
inhibits photosynthesisand limits plant
growth, fruit yields, and flower
production and is unappealing,
aesthetically. Honeydew also attracts
ants that collect and feed on the sugary
residue. In return,the ants often protect
the scales from natural enemies.I
Monitoring plants for ant activity or i
sootymold growth can help locate scale
insect infestations in landscape and
production systems. Becausearmored
scalesdo not produce honeydew, sooty
mold may not be present. Common
examples of armored scale include
euonymus scale, obscure scale,
oystershellscale,white peachscale,and
San Jose scale.To scout for scales,pay
particular attention to leaf undersides,
margins along leaf veins, leaf petioles,
and 12-inch sections (with junctions) of
stemsand bark.
'--
The Tennessee Nursery & Landscape Association
waxy covering, control efforts are most effective when directed
againstthe crawler stage. Once the wax coat has formed, many
pesticidesdo not penetratedeeplyenoughto kill the scale(Figure 3).
Severalinsecticidescanbe usedeffectively(seeRelatedLinks,below)
wheninfestationsare severe. Insecticidalsoapsand horticultural oils
are useful for controlling all stages of the scales, particularly
the crawlers. Highly refined "summer," "superior," or "supreme"
horticultural oils can be used on most ornamentalswithout causing
phytotoxic plant injury. Oils may remove the bluish tint of
ornamentals,like spruce(Piceasp.) orjunipers (Juniperussp.), which
-~ produce a waxy cast. Follow the label
rate recommendationsclosely. These
highly refinedproductscanbe usedboth
wh~n the plant is dormant and as a
summerfoliar spray when crawlers are
active. Horticultural oils may also be
used amonginteriorscapeplantings. As
a general rule, avoid applications of
horticultural oils when air temperatures
are below 500F or exceed900F.
Many beneficialorganisms,including
insectsand diseases,also reducethe
severity of scale insect outbreaks.
Severalladybeetles(Coccinellidae)feed
on eggs, crawlers, young nymphs, and
evenadult scales. Parasitismby several
wasp speciesis commonand can be an
important factor in controlling
population outbreaks. Look for small
(less than Imm), round pinholes in the
outer shell of the adult scale. When
signs of parasitism are abundant, use
insecticidal soapsand horticultural oils
to minimize mortality to the beneficial
insects,while still obtaining control of
unparasitizedcrawlers, young nymphs,
and adults.
Related Links:
UniversitYof Tennessee.
Agricultural
ExtensionService:Publications
//www.utextension.utk.edu/publications/
.Mealybugs on Ornamentals(SP290S)
and Euonymusscale (SP290W)
.Commercial Insectand Mite Control
for Trees,Shrubs,andFlowers(PB1589)
.Insect Managementin Greenhouses
(PB1594)
AUTHORNOTES:1
AssistantProfessol;Plant Sciencesand
LandscapeSystems,U1:I.A., University
ofTennessee
2 Professol;Entomologyand Plant
Pathology,U 1:1.A.,University of
Tennessee
3 AssociateProfessol;Entomology
and Plant Pathology,U 1:1.A.,University
.J""
,J
oJlennessee.'
-Tennessee
Green Times
Spring 2002
Tennessee
&
Table 1: Approximate
APRIL
.Scout apple,ash, cherry;dogwood,hibiscus,lilac, locust,pecan,and redbudfor
white peachscale (Pseudalacaspis
pentagona)
.Check pines(esp. Mugo,Austrianand red pine)for pine needlescale
(Chionaspispinifoliae)
.Look on maplesfor maple mealybug(Phenacoccusacericola)
.Scout Englishivy; euonymus,holly,andpachysandrafor euonymusscale
(Unaspiseuonym/)
.Observe fir, hemlock,spruce,and yewfor signs of hemlockscale (Abgrallaspisithacae)
JUNE
.Look for Indian wax scale (Ceroplastesceriferus)on barberry;euonymus,
holly;pyracanthus,and quince
of initial scale and mealybug
crawler activity outdoors in
Tennessee, which can be used
to develop a routine scouting
program. Many scales are
capable of multiple generations
per season.
Infestations and
susceptible
host plants should
be re-scouted at monthly
intervals once crawlers haveemerged.
.Scout fruit trees, roses,and other ornamentalsfor SanJose Scale
(Ouadrispidiotusperniciosus)
.Scout azaleasand rhododendronsfor azalea bark scale (Acanthococcus
azaleae)
.Check for oystershelJscale (Lepidosaphesulml) on apple,ash, birch, beech,
dogwood,elm, lilac, maple,and willow
periods
Interiorscapes,greenhouses,
and household
plants should be observedcontinuously.
.Check callicarpa,camellia,holly; hydrangea,maple,andyew for cottonycamellia scale
(Pulvinariafloccifera)
.Scout maples(esp. Acer rubrumandA. saccharinum)for gloomyscale
(Melanaspistenebricosa)
MI
::Y
, '- "" ' :1,"
"ill@,,:
1,1,lli1,1,llilli1,
",1,*1,*:!I*1,
.Scout hackberry,honeylocust,pear,quince,andyew (= Taxus)
for obscuremealybug(Pseudococcus
sp.)
.Scout apple,boxwood,buckeye,hibiscus,maple,pine, viburnum,and
yew for comstockmealybug(Pseudococcuscomstock/)
.Look for camellia scale (Lepidosaphescamelliae)on camellia,holly,andprivet
.Look for signs of cottony maple scale (Pulviariainnumerabilis)on alder,ash, beech,
boxwood,dogwood,elm, lilac, linden (Tilia),locust,maplesand oaks
.Scout English ivy,euonymus,holly,and pachysandrafor euonymusscale
(Unaspiseuonym/)
.Check for calico scale (Eulecaniumcerasorum)on apple, buckeye,dogwood,
elm, locust, maple,and pear
.Scout Chamaecyparis
(= Falsecypress),
cypresses~ncludingLeylandcypress),andjunipers
for juniper scale (Carulaspisjuniper/)and pinesfor pine leaf scale (Phenacaspispinifoliae)
.Observe fruit treesand ornamentalsfor Europeanfruit lecaniumscale
(Parthenolecanium
corm)and maplesand oaksfor lecanium scales (Lecaniumsp.)
JULY
.'
..Look tor obscurescale (Melanaspisobscura)on dogwood,elms,
hackberry,hickory,and oaks
AUGU
.Scout tulip poplarand magnoliafor tuliptree scale (Toumeyellaliriodendn)
N,
Landscape Asso
lio