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Cottony cushion scale - Icerya purchasi

By N A Martin (2018)

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Click to collapse Classification Info






Icerya purchasi Maskell, 1879

Click to collapse Common names Info

Cottony cushion scale, Australian bug, Australian fluted scale, Citrus fluted scale, Fluted scale, Mealy scale, White scale

Click to collapse Synonyms Info

Pericerya purchasi Silvestri, 1939

Click to collapse Taxonomic notes Info

Since Clare Morales revision of New Zealand Margarodidae in 1991, there has been a revision of the family classification that affects the genera found in New Zealand. Cottony cushion scale, Icerya purchase is now in the family Monophlebidae.

Click to collapse Biostatus and distribution Info

This adventive scale insect from Australia was first found in New Zealand in 1877 after which it became a serious pest on trees and shrubs, including citrus orchards, until controlled by the Australian cardinal ladybird, Rodolia cardinalis (Coccinellidae) and the fly, Cottony cushion scale parasitoid, Cryptochaetum iceryae (Cryptochetidae). The Cottony cushion scale has spread to many countries throughout the world. In New Zealand it is occasionally found in gardens, parks and native habitats in both North and South islands.

Conservation status: An Australian scale insect occasionally found in gardens, parks and native habitats in both North and South islands.

Click to collapse Life stages and annual cycle Info

There are two generations a year in New Zealand, though most life stages may be found in most months of the year. Many of the following details come from Clare Morales 1991 paper on the Margarodidae. This scale insect has two methods of reproduction, normal bisexual reproduction and Gynomonoecious where the hermaphrodite adult 'female' contains an ovotestis and fertilisation occurs between eggs and sperm in the same adult. The testes develops first. The occasional unfertilised egg develops into an adult winged male.

The Cottony cushion scale has four ('female') or five (male) developmental stages. The body of the adult ‘female’ is up to 10 mm long, pale to dark brown and covered in white or pale yellowish wax, with long black hairs and setae. It has one pair of black antennae and three pairs of black legs. On the underside of the head is a short rostrum that hold the stylets used for feeding. 'Females' laying eggs produce a long, white, fluted egg sac. It may contain 500-1000 bright red, oblong eggs. The eggs hatch into first instar (stage) nymphs that have pale red-brown bodies and like the adult ‘female’ three pairs of black legs and black antennae. The body is covered with a little white wax and long, glassy body setae (hairs). They squeeze out between the 'flutes' in the egg sac and settle along the mid rib and veins of the host plant leaves. Like the adult 'female' they have a ventral rostrum that holds the stylets used for feeding. When fully grown, the nymph moults into the next nymphal stage. The second and third instars are reddish-brown and covered with tufts of glassy setae, black hairs and yellow and white wax. They tend to migrate to larger twigs and branches.

Adult males are uncommon and do not live long. They have one pair of dusky wings. At the end of their abdomen they have fleshy lobes bearing tufts of long setae. Male nymphs are similar in appearance to those of the female. The last male nymph makes a fluffy oblong white cocoon in which it pupates.


Nymphs and adult females of Cottony cushion scale have sucking mouthparts. Specially shaped long rods called stylets are used for feeding. Until used for feeding the tips of the stylets held in the short sheath-like rostrum. When it wishes to feed, the scale insect moves the tip of the rostrum onto the surface of the plant. The stylets are then gradually pushed into the plant. The stylets form two tubes, one down which saliva is pumped into plant cells and the second tube through which it sucks the contents of the plant cells. If the insect inserts its stylets into the phloem, the plant vessels for transmitting sap from the leaves to other parts of the plant. The sap has a high volume of water and sugars, more than the insect needs. It excretes the excess water and sugar, which is called honeydew.

Walking, flying and dispersal

The nymphs, adult females and males have legs large enough for walking. All these stages can walk around the leaves and stems of the plant on which they are born. The main stage that spreads to new host plants is probably the first instar (stage) nymph. In other insects this stage can be disperse long distances by air. It is not known if crawlers of this species go to high points of the plant and stand up to catch the wind.

Adult males have wings as well as legs. They can walk over leaves and stems in search of females with which to mate. They can also fly to other parts of the tree or nearby colonies, and may be carried further by wind.

Click to collapse Recognition Info

Scale insects in the family Monophlebidae require specialist skills for their identification, but the only species in New Zealand, the Cottony cushion scale, is sufficiently distinctive to enable its identification on its host plants.

Adult females are large, up to 10 mm long, and have a red-brown body covered with white granular wax. When mature, they make a white, fluted, egg sac. As it enlarges the female body is tilted upwards. The nymphs have an orange brown body that is coated with white and yellow wax.

Click to collapse Natural enemies Info

No pathogens of Cottony cushion scale are known in New Zealand.


Five parasitoids are present in New Zealand. Four are wasp and one is a fly. The fly, Cottony cushion scale parasitoid, Cryptochaetum iceryae, is from Australia and was first sent to New Zealand in 1888.

Two of the wasps are hypoparasites, that is they parasitise other parasites. One, Euryischia sp. (Aphelinidae) is a parasite of the parasitic fly. The other, Coccidoctonus dubius (Encyrtidae) is a parasite of parasitic wasps.


Three of the four predators of the Cottony cushion scale in New Zealand are ladybirds. One of which is the famous Vedalia beetle or Cardinal ladybird, Rodolia cardinalis. The use of this Australian ladybird to control Cottony cushion scale in California was an early example of successful biological control.

The larvae of one of the wasp parasitoids sometimes behaves like a predator by feeding on the eggs of the scale insect.

Table: Natural enemies of Cottony cushion scale, Icerya purchasi (Hemiptera: Monophlebidae), from Plant-SyNZ database (23 March 2018). The reliability index shows the quality of evidence for the host association (0-10, 10=high quality).
Scientific NameCommon NameClassificationEnemy TypeReliability IndexBiostatus
Coccidoctonus dubius (Girault, 1915) (Wasp)Hymenoptera: Encyrtidaeparasitoid10adventive
Cryptochaetum iceryae (Williston, 1888)Cottony cushion scale parasitoid (Fly)Diptera: Cryptochetidaeparasitoid10adventive
Euryischia sp. (Wasp)Hymenoptera: Aphelinidaeparasitoid8unknown
Ophelosia crawfordi Riley, 1890 (Wasp)Hymenoptera: Pteromalidaeparasitoid10adventive
Tetracnemoidea brevicornis (Girault, 1915) (Wasp)Hymenoptera: Encyrtidaeparasitoid10adventive
Coccinella undecimpunctata Linnaeus, 1758Eleven-spotted ladybird (Beetle)Coleoptera: Coccinellidaepredator10adventive
Ophelosia crawfordi Riley, 1890 (Wasp)Hymenoptera: Pteromalidaepredator10adventive
Rodolia cardinalis (Mulsant, 1850)Cardinal ladybird (Beetle)Coleoptera: Coccinellidaepredator10adventive
Rodolia koebelei (Coquillett, 1893)Koebele's ladybird (Beetle)Coleoptera: Coccinellidaepredator10adventive

Click to collapse Host plants Info

Cottony cushion scale is found on cultivated, naturalised and native plants. It is rarely a pest because numbers are kept low though biological control. The nymphs are mainly found on leaves while the egg laying females are mostly seen on stems.

Feeding and honeydew

Like other Hemiptera, the adult female and nymphs of Cottony cushion scale have sucking mouth parts. The long stylets, special shaped rods, are held in a short rostrum on the underside of the body. When the insect wishes to feed the stylets are then gradually pushed into the plant. The inner pair of stylets, form two tubes, one through which saliva is injected into the plant and a second through which plants juices are sucked up into the insect. The adult female and nymphs of Cottony cushion scale may insert their stylets into the phloem, the plant vessels for transmitting sap from the leaves to other parts of the plant. The sap has a high volume of water and sugars, more than the insect needs. It excretes the excess water and sugar, which is called honeydew. Sooty moulds may grow on the honeydew.

Table: Host plants of the Cottony cushion scale, Icerya purchasi (Hemiptera: Monophlebidae) from Plant-SyNZ database (23 March 2018). The reliability score shows the quality of evidence for the host association (1-10, 10=high).
Common Name(s)Scientific NameFamilyReliability IndexBiostatus
Bailey's wattle, Cootamundra wattle, Golden wattleAcacia baileyana F. Muell.Leguminosae10naturalised
Bower Wattle, Narrow-leaf Bower Wattle, River WattleAcacia cognata DominLeguminosae10cultivated
Mimosa, Silver Wattle, Sydney Black WattleAcacia dealbata LinkLeguminosae10naturalised
Gossamer wattle, Sally wattle, White sallow wattleAcacia floribunda (Vent.) Willd.Leguminosae10naturalised
Kangaroo acaciaAcacia ornataLeguminosae10cultivated
MapleAcer sp.Sapindaceae7unknown
Chinese gooseberry, Kiwifruit, Yang-taoActinidia deliciosa (A.Chev.) C.F.Liang & A.R.FergusonActinidiaceae10naturalised
North Island broom, Mākaka, Maukoro, Tainoka, Tawao, MaukoroCarmichaelia australis R.Br.Leguminosae10endemic
Meyer lemon, Chinese dwarf lemonCitrus ×meyeri Yu. TanakaRutaceae10cultivated
CitrusCitrus sp.Rutaceae7unknown
Kākawariki, Kanono, Kapukiore, Karamū-kueo, Kueo (fruit), Manono, Pāpāuma, Raurēkau, ToherāoaCoprosma grandifolia Hook.f.Rubiaceae10endemic
Coastal Coprosma, TaupataCoprosma repens A.Rich.Rubiaceae10endemic
Broad-leaved fleabane, Tall fleabane, Hāka, Kaingarua, Porerarua, PouhawaikiErigeron sumatrensis Retz.Compositae10naturalised
Fatsia, Glossy-leaved paper plant, Japanese aralia, Rice paper plant, YatsudeFatsia japonica (Thunb.) Decne. & Planch.Araliaceae10naturalised
Big mountain palm, Umbrella palmHedyscepe canterburyana (C.Moore & F.Muell.) H.Wendl. & DrudePalmae10cultivated
Bay, Laurel, Sweet bayLaurus nobilis L.Lauraceae10naturalised
Apple, Crab-appleMalus sp.Rosaceae7unknown
Poataniwha, TātakaMelicope simplex A.Cunn.Rutaceae10endemic
Houkūmara, Koheriki, Tākaka, Tātaka, Wharangi, WharangipiroMelicope ternata J.R.Forst. & G.Forst.Rutaceae10endemic
Scrub pohuehue, Small-leaved pohuehue, Wire vine, Pōhue, Pōhuehue, Pōpōhue, Tororaro, WaekāhuMuehlenbeckia complexa (A.Cunn.) Meissn.Polygonaceae9indigenous, non-endemic
NgaioMyoporum laetum G.Forst.Scrophulariaceae10endemic
Red mapou, Red matipo, Māpau, Māpou, Mataira, Matipou, Takapou, Tāpau, TīpauMyrsine australis (A.Rich.) AllanPrimulaceae9endemic
Akepiro, Kūmara-kai-torouka, Tanguru, Wharangi-piroOlearia furfuracea (A.Rich.) Hook.f.Compositae10endemic
Coastal tree daisyOlearia solandri (Hook.f.) Hook.f.Compositae10endemic
 Pittosporum bracteolatum Endl.Pittosporaceae10cultivated
Kaikaro, Karo, KīhihiPittosporum crassifolium Banks & Sol. ex A.Cunn.Pittosporaceae10endemic
 Pittosporum ellipticum KirkPittosporaceae10endemic
Lemonwood, Kīhihi, TarataPittosporum eugenioides A.Cunn.Pittosporaceae10endemic
Black matipo, Kaikaro, Kōhūhū, Kohukohu, Koihu, Kōwhiwhi, Māpauriki, Pōhiri, Pōwhiri, Rautāwhiri, TāwhiriPittosporum tenuifolium Sol. ex Gaertn.Pittosporaceae10endemic
Coastal kowhaiSophora chathamica CockayneLeguminosae10endemic
Large-leaved kowhai, North Island kowhai, KōwhaiSophora tetraptera J.S. MillerLeguminosae10endemic
Milk tree, Small-leaved milk tree, Turepo, Ewekuri, Tāwari, TūrepoStreblus heterophyllus (Blume) CornerMoraceae10endemic
GorseUlex europaeus L.Leguminosae10naturalised
Furze, Gorse, WhinUlex sp.Leguminosae7naturalised
Tree nettle, Ongaonga, Taraonga, TaraongaongaUrtica ferox G.Forst.Urticaceae10endemic
HebeVeronica stricta Banks & Sol. ex Benth. var. strictaPlantaginaceae10endemic
New Zealand oak, Kauere, PūririVitex lucens KirkLabiatae10endemic

Click to collapse Additional information Info

Biological control of pests

Biological control of aphids and other herbivorous pests can reduce the impact of the pests and the need to use insecticides. The cardinal ladybird is an important predator of the Cottony cushion scale, Icerya purchase Maskell, 1879 (Hemiptera: Monophlebidae), which if uncontrolled is a serious pest of citrus trees. The scale insect also infests native and other trees. Both the ladybird and the scale insect are natives of Australia.

The ladybird arrived accidentally in New Zealand and was first reported in 1889. Later more ladybirds were imported from Australia. They were also redistributed around the country to help control the scale insect. The cardinal ladybird has been sent to many parts of the world where it contributes to the successful biological control of cottony cushion scale. Many of the ladybirds sent to California in the 1880s were from Napier, New Zealand and not Australia as is often recorded in texts on Biological Control.

The first attempt at biological control of Cottony cushion scale in New Zealand was the shipment of the fly, Cottony cushion scale parasitoid, Cryptochaetum iceryae, from Australia in 1888. However, information about its establishment was lost and confused, probably because it is less dramatic than the Cardinal ladybird. It provides good bioloical control of Cottony cushion scale in some countries.

In New Zealand, natural enemies of cottony cushion scale prevent this insect being a serious pest.

Click to collapse Information sources Info

Berry, J.A. 1990: Two parasitoid complexes: Hierodoris atychioides (Butler) (Lepidoptera: Oecophoridae) and Icerya purchasi Maskell (Homoptera: Margarodidae). New Zealand entomologist, 13: 60-62.

CABI Invasive Species Compendium: Icerya purchasi (cottony cushion scale). (Accessed 23 March 2018).

Morales CF, Bain J 1989. Icerya purchasi Maskell, cottony cushion scale (Homoptera: Margarodidae). In: Cameron PJ, Hill RL, Bain J, Thomas WP ed. A Review of Biological Control of Invertebrate Pests and Weeds in New Zealand 1847 to 1987. Technical Communication No. 10. Wallingford, Oxon, UK, CAB International. Pp. 207-211.

Morales CF. 1991. Margarodidae (Insecta: Hemiptera). Fauna of New Zealand. 21: 1-123.

Plant-SyNZ: Invertebrate herbivore-host plant association database.

Click to collapse Acknowledgements Info

The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.

Click to collapse Other images Info

Click to collapse Update history Info

1 December 2018. NA Martin. Changed symbol used for apostrophes.

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