Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Icerya purchasi
(cottony cushion scale)

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Datasheet

Icerya purchasi (cottony cushion scale)

Summary

  • Last modified
  • 28 March 2018
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Natural Enemy
  • Preferred Scientific Name
  • Icerya purchasi
  • Preferred Common Name
  • cottony cushion scale
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Arthropoda
  •       Subphylum: Uniramia
  •         Class: Insecta
  • Summary of Invasiveness
  • I. purchasi extracts significant quantities of sap from the host plant. Damage is mostly caused by sap depletion; the shoots dry up, defoliation occurs and branches or whole trees may die. Copious honeydew excreted by the scales coats the leaves, res...

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Pictures

Top of page
PictureTitleCaptionCopyright
Cottony cushion scale (I. purchasi); cluster of adults on a twig, Nairobi, Kenya.
TitleAdults
CaptionCottony cushion scale (I. purchasi); cluster of adults on a twig, Nairobi, Kenya.
CopyrightDavid J. Greathead
Cottony cushion scale (I. purchasi); cluster of adults on a twig, Nairobi, Kenya.
AdultsCottony cushion scale (I. purchasi); cluster of adults on a twig, Nairobi, Kenya.David J. Greathead
TitleCottony cushion scale
Caption
CopyrightPeter A.C. Ooi/CABI BioScience
Cottony cushion scalePeter A.C. Ooi/CABI BioScience

Identity

Top of page

Preferred Scientific Name

  • Icerya purchasi Maskell

Preferred Common Name

  • cottony cushion scale

Other Scientific Names

  • Pericerya purchasi (Maskell)

International Common Names

  • English: Australian bug; citrus fluted scale; fluted scale; mealy scale; white scale
  • Spanish: coccido acanalado; cochinilla acanalada de los agrios; cochinilla algodonosa australiana; cochinilla blanca del naranjo; escama algodonosa de los citricos (Mexico); escama harinosa; escama lanigera
  • French: cochenille australienne; cochenille flûtée; cochenille l'icerya; cochenille pericerya
  • Portuguese: cochonilha australiana; pulgao branco (Brasil)

Local Common Names

  • Brazil: pulgão branco
  • Germany: Australische wollschildlaus
  • Israel: izeriat haadaim
  • Italy: iceria di purchase
  • Japan: iseriya-kaigaramusi
  • Netherlands: geribde djeroek-luis; witte geribde schildluis
  • South Africa: australiese luis
  • Turkey: torbali kosnil

EPPO code

  • ICERPU (Icerya purchasi)

Summary of Invasiveness

Top of page I. purchasi extracts significant quantities of sap from the host plant. Damage is mostly caused by sap depletion; the shoots dry up, defoliation occurs and branches or whole trees may die. Copious honeydew excreted by the scales coats the leaves, resulting in sooty mould growth, which blocks light and air from the leaves. This reduces photosynthesis and the productivity of fruit and forest trees, and disfigures ornamental plants and fruit. Unchecked infestations of the cottony cushion scale can have a severe impact on fruit-growing and horticultural industries, and on the endemic fauna of small islands.

Taxonomic Tree

Top of page
  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Arthropoda
  •             Subphylum: Uniramia
  •                 Class: Insecta
  •                     Order: Hemiptera
  •                         Suborder: Sternorrhyncha
  •                             Unknown: Coccoidea
  •                                 Family: Monophlebidae
  •                                     Genus: Icerya
  •                                         Species: Icerya purchasi

Notes on Taxonomy and Nomenclature

Top of page

I. purchasi belongs to the scale insect family Monophlebidae, the giant scales. The genus Icerya has been poorly studied and it is possible that there are other species similar to I. purchasi living in the same geographical areas. Rao (1951) reviewed the known species of Icerya living in the Oriental Region, and a revision of the known species in Australia is currently in progress.

Description

Top of page Immature I. purchasi have black limbs and an orange-brown body that is coated with white and yellow wax. The adult female I. purchasi are easily recognized by their large size (up to 10 mm long), red-brown body colour and covering of granular, white wax. The legs, antennae and body hairs are conspicuously black. The nymphs and adult females produce long, hair-like, transparent rods of wax from the body. On reaching maturity, the female produces a white, fluted, wax ovisac with a series of uniform ridges running lengthwise over the surface. As the ovisac is produced, the rear end of the body is tilted upwards, sometimes almost perpendicular to the plant surface. The ovisac may reach the same length as the body, giving an overall combined length of up to 20 mm.

The males are rarely encountered and do not live long. The immature male stages are similar in appearance to those of the female. Pupation occurs in a fluffy, oblong white cocoon. The adult male has well developed antennae, one pair of dusky wings, a red body and tufts of long setae at the end of the abdomen.

Precise identification of Icerya species requires specimens to be mounted on microscope slides and to be studied under high magnification. The microscopic features of I. purchasi are described and illustrated by Rao (1951), Howell and Beshear (1981), Williams and Watson (1990) and Morales (1991). I. purchasi is distinctive in possessing two pairs of abdominal spiracles, three cicatrices and body setae that are conspicuously black even after staining.

Distribution

Top of page I. purchasi is generally considered to have originated in Australia. It has a wide climatic tolerance and, unlike related Icerya species, has become established as a pest in southern Europe. It is periodically discovered in greenhouses in temperate regions, but is not generally a pest in these situations. The recent discovery of relatively dense infestations in London, UK caused concern initially, but the natural enemy (vedalia beetle, Rodolia cardinalis) has apparently been accidentally introduced also; this appears to have become established in some of the London populations (Salisbury and Booth, 2004).

The distribution map includes records based on specimens of I. purchasi from the collection in the Natural History Museum, London, UK (NHM, various dates).

Distribution Table

Top of page

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

BangladeshPresentIntroduced Invasive NHM, 1980
ChinaRestricted distributionEPPO, 2014
-AnhuiPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-FujianPresentIntroduced Invasive CIE, 1971; Tao, 1999; EPPO, 2014
-GuangdongPresentIntroduced Invasive CIE, 1971; Tao, 1999; EPPO, 2014
-GuangxiPresentIntroduced Invasive CIE, 1971; Tao, 1999; EPPO, 2014
-HebeiPresentIntroduced Invasive CIE, 1971; Tao, 1999
-HenanPresentIntroduced Invasive Tao, 1999
-Hong KongPresentIntroduced Invasive CIE, 1971; Tao, 1999; EPPO, 2014
-HubeiPresentIntroduced Invasive CIE, 1971; Tao, 1999; EPPO, 2014
-HunanPresentEPPO, 2014
-JiangsuPresentIntroduced Invasive Tao, 1999; EPPO, 2014
-JiangxiPresentIntroduced Invasive Tao, 1999
-Nei MengguPresentIntroduced Invasive Tao, 1999
-ShaanxiPresentIntroduced Invasive Fan et al., 1988; Tao, 1999
-ShandongPresentIntroduced Invasive CIE, 1971; Tao, 1999; EPPO, 2014
-SichuanPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-YunnanPresentIntroduced Invasive CIE, 1971; Tao, 1999; EPPO, 2014
-ZhejiangPresentIntroduced Invasive Hua et al., 1999; EPPO, 2014
Christmas Island (Indian Ocean)PresentIntroduced Invasive CIE, 1971; EPPO, 2014
Cocos IslandsPresentIntroduced Invasive NHM, 1981
Georgia (Republic of)PresentIntroduced Invasive CIE, 1971; EPPO, 2014
IndiaRestricted distributionEPPO, 2014
-Andhra PradeshPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-GujaratPresentIntroduced Invasive NHM, 1985
-KarnatakaPresentIntroduced Invasive CIE, 1971
-KeralaPresentIntroduced Invasive Rao, 1951; EPPO, 2014
-LakshadweepPresentIntroduced Invasive NHM, 1988
-Madhya PradeshPresentMeshram and Vijayaraghavan, 2004
-MaharashtraPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-OdishaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-Tamil NaduPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-Uttar PradeshPresentVerma et al., 2012
-West BengalPresentIntroduced Invasive Konar, 1998
IndonesiaRestricted distributionEPPO, 2014
-Irian JayaPresentIntroduced Invasive CIE, 1971
-JavaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-SulawesiPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-SumatraPresentIntroduced Invasive CIE, 1971; EPPO, 2014
IranPresentIntroduced Invasive CIE, 1971; EPPO, 2014
IraqPresentIntroduced Invasive CIE, 1971; EPPO, 2014
IsraelWidespreadIntroduced Invasive CIE, 1971; EPPO, 2014
JapanPresentEPPO, 2014
-HonshuPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-KyushuPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-Ryukyu ArchipelagoPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-ShikokuPresentIntroduced Invasive CIE, 1971
JordanPresentIntroduced Invasive CIE, 1971; EPPO, 2014
Korea, DPRPresentIntroduced Invasive CIE, 1971
Korea, Republic ofPresentIntroduced Invasive APPPC, 1987; EPPO, 2014
LebanonPresentIntroduced Invasive CIE, 1971; EPPO, 2014
MalaysiaPresentIntroduced Invasive CIE, 1971; Waterhouse, 1993; EPPO, 2014
-Peninsular MalaysiaPresentIntroduced Invasive CIE, 1971
MaldivesPresentIntroduced Invasive Watson et al., 1995
PakistanPresentIntroduced Invasive CIE, 1971; EPPO, 2014
Saudi ArabiaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
SingaporePresentIntroduced Invasive Waterhouse, 1993
Sri LankaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
SyriaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
TaiwanPresentIntroduced Invasive CIE, 1971; Tao, 1999; Wong et al., 1999; EPPO, 2014
ThailandPresentIntroduced Invasive Waterhouse, 1993
TurkeyPresentIntroduced Invasive CIE, 1971; EPPO, 2014
VietnamPresentIntroduced Invasive CIE, 1971; Waterhouse, 1993; EPPO, 2014
YemenPresentEPPO, 2014

Africa

AlgeriaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
AngolaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
Cape VerdePresentIntroduced Invasive CIE, 1971; EPPO, 2014
CongoPresentIntroduced Invasive CIE, 1971
Congo Democratic RepublicPresentEPPO, 2014
EgyptPresentIntroduced Invasive CIE, 1971; EPPO, 2014
EthiopiaPresentIntroduced Invasive CIE, 1971; Getu, 1996; EPPO, 2014
KenyaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
LibyaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
MadagascarPresentIntroduced Invasive CIE, 1971; EPPO, 2014
MalawiPresentIntroduced Invasive CIE, 1971; EPPO, 2014
MauritiusPresentIntroduced Invasive CIE, 1971; EPPO, 2014
MoroccoPresentIntroduced Invasive CIE, 1971; EPPO, 2014
MozambiquePresentIntroduced Invasive CIE, 1971; EPPO, 2014
Saint HelenaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-AscensionPresentIntroduced Invasive NHM, 1977
Sao Tome and PrincipePresentIntroduced Invasive CIE, 1971; EPPO, 2014
SenegalPresentIntroduced Invasive CIE, 1971; EPPO, 2014
SeychellesPresentIntroduced Invasive CIE, 1971; EPPO, 2014
SomaliaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
South AfricaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
Spain
-Canary IslandsPresentIntroduced Invasive CIE, 1971; EPPO, 2014
SudanPresentIntroduced Invasive CIE, 1971; EPPO, 2014
TanzaniaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
TogoPresentIntroduced Invasive CIE, 1971; EPPO, 2014
TunisiaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
UgandaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
ZambiaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
ZimbabwePresentIntroduced Invasive CIE, 1971; EPPO, 2014

North America

BermudaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
MexicoPresentIntroduced Invasive CIE, 1971; EPPO, 2014
USARestricted distributionEPPO, 2014
-AlabamaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-ArizonaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-CaliforniaPresentIntroducedca 1868 Invasive CIE, 1971; Gill, 1993; EPPO, 2014
-FloridaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-GeorgiaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-HawaiiPresentIntroducedpre-1890 Invasive CIE, 1971; EPPO, 2014
-LouisianaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-MississippiPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-MontanaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-New MexicoPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-North CarolinaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-OklahomaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-South CarolinaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-TexasPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-VirginiaPresentIntroduced Invasive CIE, 1971; EPPO, 2014

Central America and Caribbean

Antigua and BarbudaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
BahamasPresentIntroduced Invasive CIE, 1971; EPPO, 2014
BarbadosPresentIntroduced Invasive CIE, 1971; Bennett and Alam, 1985; EPPO, 2014
Cayman IslandsPresentIntroduced Invasive NHM, 1970
CubaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
CuraçaoPresentIntroduced Invasive CIE, 1971
DominicaPresentIntroduced Invasive NHM, 1985
Dominican RepublicPresentIntroduced Invasive CIE, 1971; EPPO, 2014
El SalvadorPresentIntroduced Invasive CIE, 1971; EPPO, 2014
GuadeloupePresentIntroduced Invasive CIE, 1971; EPPO, 2014
GuatemalaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
HaitiPresentIntroduced Invasive NHM, 1972; NHM, 1973
JamaicaPresentIntroduced Invasive NHM, 1964
MartiniquePresentIntroduced Invasive CIE, 1971; EPPO, 2014
MontserratPresentIntroduced Invasive CIE, 1971; EPPO, 2014
Puerto RicoPresentIntroduced Invasive CIE, 1971; EPPO, 2014
Saint Kitts and NevisPresentIntroduced Invasive NHM, 1971; EPPO, 2014
Saint LuciaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
Trinidad and TobagoPresentIntroduced Invasive CIE, 1971; EPPO, 2014

South America

ArgentinaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
BoliviaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
BrazilPresentEPPO, 2014
-AmazonasPresentIntroduced Invasive CIE, 1971
-BahiaPresentIntroduced Invasive CIE, 1971
-CearaPresentIntroduced Invasive CIE, 1971
-Espirito SantoPresentCulik et al., 2007; EPPO, 2014
-Minas GeraisPresentIntroduced Invasive CIE, 1971
-ParaPresentIntroduced Invasive CIE, 1971
-ParaibaPresentIntroduced Invasive CIE, 1971
-ParanaPresentIntroduced Invasive CIE, 1971
-PernambucoPresentIntroduced Invasive CIE, 1971
-PiauiPresentIntroduced Invasive CIE, 1971
-Rio de JaneiroPresentIntroduced Invasive CIE, 1971
-Rio Grande do SulPresentIntroduced Invasive CIE, 1971
-Santa CatarinaPresentIntroduced Invasive CIE, 1971
-Sao PauloPresentIntroduced Invasive CIE, 1971
ChilePresentIntroduced Invasive CIE, 1971; EPPO, 2014
ColombiaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
EcuadorPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-Galapagos IslandsPresentIntroduced Invasive Peck et al., 1998
GuyanaPresentIntroduced Invasive NHM, 1979; NHM, 1995
ParaguayPresentIntroduced Invasive CIE, 1971; EPPO, 2014
PeruPresentIntroduced Invasive CIE, 1971; EPPO, 2014
UruguayPresentIntroduced Invasive CIE, 1971; EPPO, 2014
VenezuelaPresentIntroduced Invasive CIE, 1971; EPPO, 2014

Europe

AlbaniaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
BulgariaPresentEPPO, 2014
CroatiaPresentEPPO, 2014
CyprusWidespreadIntroduced Invasive CIE, 1971; EPPO, 2014
FranceRestricted distributionIntroduced Invasive CIE, 1971; Matile-Ferrero et al., 1999; EPPO, 2014
-CorsicaPresentIntroduced Invasive CIE, 1971; Foldi, 2003; EPPO, 2014
GermanyPresentSchönfeld, 2015Brandenburg
GibraltarPresentIntroduced Invasive CIE, 1971; EPPO, 2014
GreecePresentIntroduced Invasive CIE, 1971; Papadopoulou and Chryssohoides, 2012; EPPO, 2014
-CretePresentEPPO, 2014
HungaryPresentEPPO, 2014
ItalyPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-SardiniaPresentEPPO, 2014
-SicilyPresentIntroduced Invasive Russo et al., 2003; EPPO, 2014
MaltaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
PortugalPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-AzoresPresentIntroduced Invasive CIE, 1971; EPPO, 2014
-MadeiraPresentIntroduced Invasive CIE, 1971; EPPO, 2014
RomaniaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
Russian FederationPresentIntroduced Invasive CIE, 1971; EPPO, 2014
SerbiaPresentEPPO, 2014
SlovakiaPresentKollár et al., 2016
SpainPresentIntroduced Invasive CIE, 1971; Getu, 1996; EPPO, 2014
SwitzerlandPresentIntroduced Invasive CIE, 1971; EPPO, 2014
UKPresentWatson and Malumphy, 2004; Malumphy, 2013
Yugoslavia (Serbia and Montenegro)PresentIntroduced Invasive CIE, 1971

Oceania

AustraliaRestricted distributionEPPO, 2014
-Lord Howe Is.PresentWilliams and Watson, 1990
-New South WalesPresentNative Not invasive CIE, 1971; EPPO, 2014
-QueenslandPresentNative Not invasive CIE, 1971; EPPO, 2014
-South AustraliaPresentNative Not invasive CIE, 1971; EPPO, 2014
-TasmaniaPresentCIE, 1971; EPPO, 2014
-VictoriaPresentNative Not invasive CIE, 1971; EPPO, 2014
FijiPresentIntroduced Invasive CIE, 1971; Williams and Watson, 1990; EPPO, 2014
French PolynesiaPresentIntroduced Invasive CIE, 1971; Williams and Watson, 1990; EPPO, 2014
GuamPresentIntroduced Invasive CIE, 1971; EPPO, 2014
KiribatiPresentIntroduced Invasive Beardsley, 1966
Marshall IslandsPresentIntroduced Invasive CIE, 1971; EPPO, 2014
Micronesia, Federated states ofPresentIntroduced Invasive CIE, 1971; EPPO, 2014
New CaledoniaPresentIntroduced Invasive CIE, 1971; EPPO, 2014
New ZealandPresentIntroduced Invasive CIE, 1971; EPPO, 2014
Norfolk IslandPresentIntroduced Invasive CIE, 1971; Williams and Watson, 1990; EPPO, 2014
Northern Mariana IslandsPresentEPPO, 2014
PalauPresentEPPO, 2014
Papua New GuineaPresentCIE, 1971; Williams and Watson, 1990; EPPO, 2014
Solomon IslandsPresentIntroduced Invasive CIE, 1971; Williams and Watson, 1990; EPPO, 2014
TongaPresentIntroduced Invasive CIE, 1971; Williams and Watson, 1990; EPPO, 2014
US Minor Outlying IslandsPresentEPPO, 2014

History of Introduction and Spread

Top of page I. purchasi is native to Australia; it was accidentally introduced to California in about 1868 and devastated the citrus industry there until a natural enemy from Australia was introduced in 1888. This was the first ever example of successful classical biological control. The pest also reached New Zealand and South Africa at about the same time, and has subsequently spread widely through most of the tropical and subtropical countries of the world (Bartlett, 1978). Recently it has begun to extend its range northwards, being recorded for the first time breeding outdoors in Paris, France in 2000 (Matile-Ferrero et al., 1999) and in London, UK in 2002 (G Watson, [address available from CABI], personal communication, 2004); this may be due to climate warming (G Watson, [address available from CABI], personal communication, 2004).

Risk of Introduction

Top of page I. purchasi is widespread throughout the tropical and warmer temperate regions. It is probable that it occurs in more countries than are indicated by the distribution map, and it would easily establish in any remaining areas that have appropriate climatic conditions.

Accidental introduction to new territories is possible through the movement of infested live plants through shipping or air transport/mail. This insect moves between countries on live plant material, particularly in shipments of whole ornamental plants and fruit trees.

Hosts/Species Affected

Top of page The list of hosts is not exhaustive. I. purchasi lives on a wide variety of hosts, especially woody plants.

Host Plants and Other Plants Affected

Top of page
Plant nameFamilyContext
Acacia (wattles)FabaceaeMain
Acacia confusaFabaceaeMain
Acacia dealbata (acacia bernier)FabaceaeOther
Acalypha (Copperleaf)EuphorbiaceaeMain
Albizia julibrissin (silk tree)FabaceaeMain
Albizia procera (white siris)FabaceaeOther
BaccharisAsteraceaeOther
BegoniaBegoniaceaeOther
Buxus sempervirens (common boxwood)BuxaceaeOther
Caesalpinia (divi-divi)FabaceaeOther
CajanusFabaceaeOther
Cajanus cajan (pigeon pea)FabaceaeOther
CamelliaTheaceaeOther
Cassia (sennas)FabaceaeOther
Casuarina (beefwood)CasuarinaceaeOther
Casuarina equisetifolia (casuarina)CasuarinaceaeMain
ChoisyaRutaceaeOther
Choisya ternata (mexican orange-blossom)RutaceaeOther
CitrusRutaceaeMain
CrotalariaFabaceaeOther
Cytisus (Broom)FabaceaeMain
Desmodium (tick clovers)FabaceaeOther
ElaeagnusElaeagnaceaeOther
Euphorbia (spurges)EuphorbiaceaeOther
Fragaria (strawberry)RosaceaeOther
FuchsiaOnagraceaeOther
Glycine sojaFabaceaeMain
HebeScrophulariaceaeOther
Hedera helix (ivy)AraliaceaeOther
Hydrangea (hydrangeas)HydrangeaceaeOther
Impatiens (balsam)BalsaminaceaeOther
Indigofera (indigo)FabaceaeMain
Jasminum (jasmine)OleaceaeOther
Juncus (rushes)JuncaceaeOther
Lantana camara (lantana)VerbenaceaeWild host
Laurus nobilis (sweet bay)LauraceaeOther
Macadamia integrifolia (macadamia nut)ProteaceaeOther
Malpighia glabra (acerola)MalpighiaceaeOther
Mangifera indica (mango)AnacardiaceaeMain
Maranta bicolorMarantaceaeOther
Medicago sativa (lucerne)FabaceaeOther
Mimosa (sensitive plants)FabaceaeOther
Morus alba (mora)MoraceaeMain
Morus nigra (black mulberry)MoraceaeOther
Nandina domestica (Nandina)BerberidaceaeOther
Pelargonium (pelargoniums)GeraniaceaeOther
PittosporumPittosporaceaeOther
Pittosporum tobira (Japanese pittosporum)PittosporaceaeOther
PlumbagoPlumbaginaceaeOther
Plumbago zeylanicaPlumbaginaceaeOther
Prunus (stone fruit)RosaceaeOther
Psidium guajava (guava)MyrtaceaeMain
Psophocarpus tetragonolobus (winged bean)FabaceaeMain
Punica granatum (pomegranate)PunicaceaeOther
Pyracantha coccinea (Scarlet firethorn)RosaceaeOther
Quercus (oaks)FagaceaeOther
Ricinus communis (castor bean)EuphorbiaceaeOther
Rosa (roses)RosaceaeMain
Rosmarinus officinalis (rosemary)LamiaceaeOther
Schinus (pepper tree)AnacardiaceaeOther
Senecio (Groundsel)AsteraceaeOther
Spartium junceum (Spanish broom)FabaceaeOther
SpiraeaRosaceaeOther
Syringa (lilac)OleaceaeOther
Ulex europaeus (gorse)FabaceaeMain
Virgilia capensis (snowdrop tree)FabaceaeOther

Growth Stages

Top of page Flowering stage, Fruiting stage, Vegetative growing stage

Symptoms

Top of page Sap depletion may lead to wilting, leaf drop, dieback, and stunted growth. As with most sap-sucking insects, the production of honeydew leads to the growth of sooty mould.

List of Symptoms/Signs

Top of page
SignLife StagesType
Growing point / dieback
Leaves / abnormal leaf fall
Leaves / honeydew or sooty mould
Leaves / honeydew or sooty mould
Stems / external feeding
Stems / honeydew or sooty mould
Whole plant / dwarfing

Biology and Ecology

Top of page I. purchasi have four ('female') or five (male) developmental stages. As with all scale insects, the females do not produce wings and look similar to the immature stages. The males possess a single pair of dusky wings. However the 'females' are actually hermaphrodites with fertilization occurring between the eggs and the sperm of the same individual. Sexually functional males are occasionally produced from unfertilized eggs, but mating is not necessary for reproduction (Morales, 1992).

The adult females produce 500 to 2000 bright-red, oblong eggs over a period of 2 to 3 months. The number of eggs produced depends on the body size, condition of the host and climatic conditions. After leaving the egg sac, the crawlers settle along the midribs and veins of the leaves. The next two instars migrate to the larger twigs and branches and eventually moult into the adult 'female' (Morales, 1992). There are two to four generations per year. Cottony cushion scale infestations are often attended by ants that are attracted to the sugary honeydew excreted by the scales (Getu, 1996).


Natural enemies

Top of page
Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Cardiastethus nazarenus Predator Adults/Eggs/Nymphs
Cryptochetum iceryae Parasite Nymphs Bermuda;Chile;Egypt;India;Israel;New Zealand;Peru;Sao Tome and Principe;South Australia;St Kitts Nevis;USA Acacia baileyana; Acalypha; Citrus; Erythrina umbrosus; fruit trees; ornamental plants; roses; Tamarix
Cryptochetum monophlebi Parasite USA Citrus
Cryptolaemus montrouzieri Predator
Decadiomus hughesi Predator Adults/Nymphs
Ereunetis miniuscula Predator Adults/Nymphs
Euseius gossipi Predator Adults/Nymphs
Hippodamia convergens Predator Adults/Nymphs Ecuador Citrus
Holcocera iceryaella Predator Adults/Nymphs
Laetilia coccidivora Predator Adults/Nymphs
Macrosiagon octomaculatum Parasite
Pyroderces rileyi Predator Adults/Nymphs
Rodolia cardinalis Predator Adults/Eggs/Nymphs Antigua; Ascension; Australia; South Australia; Bahamas; Barbados; Bermuda; California; Cayman Islands; Chile; Cyprus; Ecuador; Egypt; Ethiopia; France; Greece; Guam; Hawaii; Hong Kong; Israel; Italy; Kenya; Madagascar; Malta; Montserrat; New Zealand; Peru; Philippines; Portugal; Puerto Rico; Republic of Georgia; Sao Tome and Principe; Senegal; South Africa; Spain; Sri Lanka; St Helena; St Kitts Nevis; Switzerland; Taiwan; Uruguay; USA; USSR; Venezuela; Yugoslavia Acacia; Acacia baileyana; Acalypha; Casuarina; Citrus; fruit trees; orchards; ornamental plants; pigeon peas; roses; Tamarix
Rodolia fumida Predator Adults/Nymphs Hawaii Citrus
Rodolia iceryae Predator Adults/Eggs/Nymphs USA Citrus
Rodolia koebelei Predator Adults/Eggs/Nymphs Hawaii; USA Citrus
Rodolia pumila Predator Adults/Nymphs Hawaii Citrus
Rodolia rufipilosa Predator Adults/Nymphs USSR
Stathmopoda melanochra Predator Adults/Nymphs
Syneura cocciphila USSR

Notes on Natural Enemies

Top of page Most of the recorded distributions of the natural enemies of I. purchasi are species introduced from other geographical areas for its control. The origin of I. purchasi is generally considered to be Australia, and other natural enemies are likely to occur in its natural habitat.

Means of Movement and Dispersal

Top of page Natural Dispersal (Non-Biotic Factors)

The dispersal stage of the giant mealybugs is the first-instar crawler stage (G Watson, [address available from CABI], personal communication, 2004); these are often dispersed passively in the wind, and have been recorded being taken by the wind to an altitude of 6 metres and a distance of 3.5 kilometres (Hill, 1980).

Vector Transmission

The crawlers may also be carried passively by animals and people that come into contact with the host plant.

Agricultural Practices

Harvesting infested plant material, e.g. fruit, aids dispersal by scattering the crawlers into the air, where the wind may carry them away. Prunings of infested plants, and the clothing, tools and vehicles of agricultural workers, can become contaminated with the crawlers and so aid in their dispersal.

Plant Trade

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Plant parts liable to carry the pest in trade/transportPest stagesBorne internallyBorne externallyVisibility of pest or symptoms
Bark larvae Yes Pest or symptoms usually visible to the naked eye
Flowers/Inflorescences/Cones/Calyx adults; eggs; larvae; nymphs; pupae Yes Pest or symptoms usually visible to the naked eye
Fruits (inc. pods) adults; eggs; larvae; nymphs; pupae Yes Pest or symptoms usually visible to the naked eye
Leaves adults; eggs; larvae; nymphs; pupae Yes Pest or symptoms usually visible to the naked eye
Seedlings/Micropropagated plants adults; eggs; larvae; nymphs; pupae Yes Pest or symptoms usually visible to the naked eye
Stems (above ground)/Shoots/Trunks/Branches adults; eggs; larvae; nymphs; pupae Yes Pest or symptoms usually visible to the naked eye
Plant parts not known to carry the pest in trade/transport
Bulbs/Tubers/Corms/Rhizomes
Growing medium accompanying plants
Roots
True seeds (inc. grain)
Wood

Wood Packaging

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Wood Packaging liable to carry the pest in trade/transportTimber typeUsed as packing
Solid wood packing material with bark No
Wood Packaging not known to carry the pest in trade/transport
Loose wood packing material
Non-wood
Processed or treated wood
Solid wood packing material without bark

Impact Summary

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CategoryImpact
Animal/plant collections Negative
Animal/plant products Negative
Biodiversity (generally) Negative
Crop production Negative
Environment (generally) None
Fisheries / aquaculture None
Forestry production Negative
Human health None
Livestock production None
Native fauna None
Native flora None
Rare/protected species Negative
Tourism None
Trade/international relations None
Transport/travel None

Impact

Top of page Damage to the plant by I. purchasi is mostly caused by sap depletion; the shoots dry up and die, and defoliation occurs. In addition, the copious quantities of honeydew produced by the scales coat the leaves, blocking the stomata and impeding gas exchange. Such fouling frequently results in the growth of sooty moulds over the leaf surfaces, which blocks light from the mesophyll, so reducing photosynthesis.

I. purchasi is a particular pest of citrus, Acacia spp., Casuarina spp. and Pittosporum spp., but it can damage many types of fruit and forest trees, and ornamental shrubs and trees. After its introduction into California, USA, in the late nineteenth century, it was recorded devastating citrus orchards, killing even large trees. By 1887, the problem on citrus had increased to such serious proportions that the entire citrus industry of California was threatened with destruction (Bartlett, 1978). Serious damage to citrus orchards by I. purchasi was also recorded in many other countries when the cottony cushion scale first arrived (Williams and Watson, 1990), but with successful biological control this insect has become relatively unimportant in fruit orchards today.

In Anhui, China, I. purchasi is one of the most important pests of pomegranates (Punica granatum) (Wang et al., 2002), and in Zhejiang, China, the cottony cushion scale is the main pest damaging Liquidambar formosana (Formosan-gum) (Hua et al., 1999). In Israel, the cottony cushion scale was a serious pest in the northern part of the country until biological control became established, which reduced it to minor pest status (Ben-Dov, 1995).

Impact: Biodiversity

Top of page The relatively recent establishment of I. purchasi in the Galapagos Islands (Peck et al., 1998) has caused concern because the pest has attacked a wide range of plants, including some of the endemic flora, and could endanger the native flora and the fauna dependant on it (Roque-Albelo, 2003). A biological control programme is currently underway (Causton, 2003).

Detection and Inspection

Top of page I. purchasi is usually found along major veins on the lower surfaces of the leaves, and on the stems of host plants. It congregates in large masses and is very conspicuous. Long-established infestations are often surrounded by sooty mould growth, and may be attended by ants.

Similarities to Other Species/Conditions

Top of page I. purchasi is most similar to the Seychelles scale, Icerya seychellarum, but differs by having granular white wax covering the body, whereas I. seychellarum has tufts of yellow wax along the dorsum and around the margins; and in lacking conspicuous black body hairs. In addition, the ovisac of I. purchasi is large and fluted, whereas that of I. seychellarum is smaller, and fluffy rather than fluted. I. seychellarum does not congregate in masses.

Slide-mounted specimens of I. purchasi can be distinguished from the other common species of Icerya by the presence of two pairs of abdominal spiracles, three cicatrices and black body hairs.

Prevention and Control

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Chemical Control

All life stages of I. purchasi are covered with wax, which reduces the effectiveness of most chemical insecticides. In addition, the use of insecticides prevents regulation by natural enemies, which has proved to be highly successful with this species. In the Spanish citrus industry, it is important to only use pesticides when absolutely necessary to ensure that the biological control agents of the citrus pests are not significantly injured; side-effect testing of pesticides on the control agents has been routinely carried out in Spain for many years (Jacas Miret and Garcia Mari, 2001).

The insect growth regulator pyriproxyfen has been found to be as effective in controlling I. purchasi (Gokkes et al., 1989). Good control was achieved when applied alone or with 0.5% mineral oil (Peleg, 1989). Another growth regulator, buprofezin, gave 100% mortality of crawlers and 31% decreased egg hatch when the adults were sprayed with it (Mendel et al., 1991).

In Italy, trials on the effect of azadirachtin A (extracted from neem) on the development and fecundity of Rodolia cardinalis indicated that use of this organic insecticide can adversely affect biological control of the cottony cushion scale (Heimbach, 2002).

Biological Control

The regulation of I. purchasi by natural enemies is one of the classic success stories in biological control. When I. purchasi established in California, USA in 1868/1869, it was apparent that it could be a major impediment to citrus production. In 1888, the United States Department of Agriculture (USDA) imported various natural enemies from Australia, including the vedalia beetle, Rodolia cardinalis. Vedalia immediately proved highly effective in controlling I. purchasi and has subsequently been distributed to about 57 countries (Bartlett, 1978). It has continued to be effective in controlling I. purchasi, except in areas where the indiscriminate use of insecticides has killed the predator. In areas with extreme winters, which kill off the vedalia populations, periodic re-introduction has been necessary.

I. purchasi living on plants such as Spartium junceum, which contain alkaloids, are not completely controlled by R. cardinalis. Caltagirone and Doutt (1989) suggested that these plants (with residual populations of the scale) provide permanent sources of vedalia that will disperse into new infestations of scale on citrus and bring them under control.

A detailed history of the introduction of the vedalia beetle into California, USA, is given by Caltagirone and Doutt (1989).

The parasitoid Cryptochaetum iceryae has also proved to be effective in regulating I. purchasi populations. Adult C. iceryae are sensitive to heat and aridity and are most effective in regulating cottony cushion scale populations in cooler coastal areas. In more arid and hot inland areas, vedalia beetles are more effective. Studies in inland California (Quezada and DeBach, 1973) have shown that the two natural enemies seasonally share their prey in different proportions and are fairly even in their competitive abilities, Rodolia usually taking more prey during summer and autumn and Cryptochaetum taking more during winter and early spring. Competition between the two natural enemies did not increase host survival and these studies provide strong support for the importation of multiple natural enemies.

Various other natural enemies have been tried against I. purchasi, but with little success.

Careful management is necessary when using pesticides against other pests if biological control of I. purchasi is in operation, because damage to the populations of biocontrol agent can cause an outbreak of I. purchasi, as recorded in South Africa by Hattingh and Tate (1995).

Ants attending I. purchasi infestations to collect the sugary honeydew excreted (Getu, 1996), may defend the scales from attack by their natural enemies, so making the pest problem worse. If large numbers of ants attend a heavy infestation of the scale, it may be worthwhile controlling the ants to help the natural enemies bring the scale population under control quickly.

References

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