Icerya purchasi

Icerya purchasi (common name: cottony cushion scale) is a scale insect that feeds on more than 65 families of woody plants,[1] most notably on Citrus and Pittosporum. Originally described in 1878 from specimens collected in New Zealand as pests of kangaroo acacia,[2] it is now found worldwide where citrus crops are grown. The cottony cushion scale originates from Australia.[3]

Icerya purchasi
Icerya purchasi , female
Scientific classification
I. purchasi
Binomial name
Icerya purchasi
Maskell, 1878
  • Icerya purchasi crawii Cockerell, 1897
  • Icerya purchasi maskelli Cockerell, 1897
  • Icerya purchasi citriperda Hempel, 1920

Life cycle

Icerya purchasi 1435060
Small colony

This scale infests twigs and branches. The mature hermaphrodite is oval in shape, reddish-brown with black hairs, 5 mm long. When mature, the insect remains stationary, attaches itself to the plant by waxy secretions, and produces a white egg sac in grooves, by extrusion, in the body which encases hundreds of red eggs. The egg sac will grow to be two to three times as long as the body. Newly hatched nymphs are the primary dispersal stage, with dispersion known to occur by wind and by crawling. Early stage nymphs feed from the midrib veins of leaves and small twigs, and do the bulk of the damage. At each molt, they leave at the old feeding point the former skin and the waxy secretions in which they had covered themselves and from which their common name is derived. Unlike many other scale insects, they retain legs and a limited mobility in all life stages. Older nymphs migrate to larger twigs and eventually as adults to branches and the trunk. Their life cycle is highly temperature dependent, as the length of time in each stage of life is longer in cold temperatures than high temperatures.

In addition to the direct damage from sap sucking, the insects also secrete honeydew, on which sooty mold often grows and causes further damage to the host plant. Some ants will also consume this honeydew.


'It turns out that females in these hermaphrodite insects are not really fertilizing their eggs themselves, but instead are having this done by a parasitic tissue that infects them at birth,' says Laura Ross of Oxford University's Department of Zoology. ‘It seems that this infectious tissue derives from left-over sperm from their father, who has found a sneaky way of having more children by mating with his daughters.'[4]

True males are uncommon to rare overall, and in many infestations are not present. Pure females are unknown. Self-fertilization by a hermaphrodite will produce only hermaphrodites. Matings of a male and hermaphrodite will produce both males and hermaphrodites.[5]

Biological control

Rodolia cardinalis USDA
Rodolia cardinalis feeding on cottony cushion scale

Icerya purchasi is important as one of the first major successes of biological control. Importations of the vedalia ladybird (Rodolia cardinalis) in 1888-1889 by C. V. Riley, later head of the USDA's Division of Entomology, resulted in swift reductions of I. purchasi populations, saving the burgeoning Californian citrus industry from this destructive pest.

A second biological control, the parasitic fly Cryptochetum iceryae has also been introduced to California as an additional control vector. Use of insecticides as a control is recommended only if no biological control species is present. Imidacloprid is especially contraindicated, since it has no effect on this species, but is very toxic to Rodolia cardinalis.


  1. ^ ScaleNet
  2. ^ Maskell, W.M. 1879 (1878). On some Coccidae in New Zealand. Transactions and Proceedings of the New Zealand Institute 11: 187-228.
  3. ^ Nair, K. S. S. (2007). Tropical Forest Insect Pests: Ecology, Impact, and Management. Cambridge University Press. ISBN 9781139464857.
  4. ^
  5. ^ Gardner, Andy; Ross, Laura (2011). "The Evolution of Hermaphroditism by an Infectious Male-Derived Cell Lineage: An Inclusive-Fitness Analysis". The American Naturalist. 178 (2): 191–201. doi:10.1086/660823. PMID 21750383. Lay summaryNational Geographic News (August 17, 2011).

External links

Albert Koebele

Albert Koebele (28 February 1853 - 28 December 1924) was an economic entomologist and a pioneer in the use of biological controls to manage insect pests.

Alexander Craw

Alexander Craw (3 August 1850 – 28 June 1908) was a pioneer American economic entomologist. He was the first American entomologist to work in quarantine protection against foreign pests arriving by ship to San Francisco, California. Along with Albert Koebele he was involved in the introduction of Rodolia cardinalis from Australia to control Icerya purchasi. He was also involved in the introduction of Rhyzobius ventralis to control the black scale, Saissetia oleae.Craw was born in Ayr, South Ayrshire, Scotland where he trained in horticulture. He worked in the Royal nurseries at Ascot and at Martins and Son, Cottingham before he moved to California in 1873 and worked as a horticulturist there. After two years in San Diego, he worked at the Wolfskill orange groves in Los Angeles and became a member of the Horticultural Commission of California. From 1890 he worked in the port of San Francisco as a quarantine officer to prevent the entry of potential pests. In 1904 he quit his California position and took up a position as superintendent of entomology to the board of agriculture and forestry in Hawaii where he established quarantine procedures. His position in California was taken up by E.M. Ehrhorn. Craw died of kidney failure at Wawona in the Yosemite valley at the home of his sister. His papers were destroyed in fires following the 1906 San Francisco earthquake.


Androdioecy is a reproductive system characterized by the coexistence of males and hermaphrodites. Androdioecy is rare in comparison to the other major reproductive systems: dioecy, gynodioecy and hermaphroditism. In animals, androdioecy has been considered an important stepping stone in the transition from dioecy to hermaphroditism, and vice versa.

Biological pest control

Biological control or biocontrol is a method of controlling pests such as insects, mites, weeds and plant diseases using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also involves an active human management role. It can be an important component of integrated pest management (IPM) programs.

There are three basic strategies for biological pest control: classical (importation), where a natural enemy of a pest is introduced in the hope of achieving control; inductive (augmentation), in which a large population of natural enemies are administered for quick pest control; and inoculative (conservation), in which measures are taken to maintain natural enemies through regular reestablishment.Natural enemies of insect pests, also known as biological control agents, include predators, parasitoids, pathogens, and competitors. Biological control agents of plant diseases are most often referred to as antagonists. Biological control agents of weeds include seed predators, herbivores and plant pathogens.

Biological control can have side-effects on biodiversity through attacks on non-target species by any of the same mechanisms, especially when a species is introduced without thorough understanding of the possible consequences.


Icerya is a genus of scale insects in the family Monophlebidae.

List of animal species introduced to the Hawaiian Islands

This is a list of animal species introduced to the Hawaiian Islands.

List of introduced species

A complete list of introduced species for even quite small areas of the world would be dauntingly long. Humans have introduced more different species to new environments than any single document can hope to record. This list is generally for established species with truly wild populations— not kept domestically—that have been seen numerous times, and have breeding populations. While most introduced species can cause a negative impact to new environments they reach, some can have a positive impact, just for conservation purpose.

List of invasive species in Asia

This is a list of invasive species in Asia. A species is regarded as invasive if it has been introduced by human action to a location, area, or region where it did not previously occur naturally (i.e., is not a native species), becomes capable of establishing a breeding population in the new location without further intervention by humans, and becomes a pest in the new location, directly threatening agriculture and/or the local biodiversity.

The term invasive species refers to a subset of those species defined as introduced species. If a species has been introduced but remains local, and is not problematic to agriculture or to the local biodiversity, then it cannot be considered to be an invasive species and does not belong on this list.

List of invasive species in Colombia

Colombia's governmental organization that oversees and manages natural parks within its national borders, Parques Nacionales Naturales de Colombia, has provided an official list of species that are considered to be invasive under the following resolutions:

Resolution 848 of 2008

Resolution 132 of 2010

Resolution 207 of 2010

Resolution 654 of 2011

List of invasive species in Japan

A number of introduced species, some of which have become invasive species, have been added to Japan's native flora and fauna.

List of invasive species in Portugal

This is a list of invasive species in Portugal. The species tagged with a cross (†) have the legal status of invasive species (Decreto-Lei n.º 565/99 de 21 de Dezembro). The remaining are considered invasive by investigators in Portugal.

List of pests and diseases of roses

Roses (Rosa species) are susceptible to a number of pests, diseases and disorders. A large number of the problems affecting roses are seasonal and climatic. Some varieties of roses are naturally more resistant or immune than others to certain pests and diseases. Cultivation requirements of individual rose species and cultivars, when observed, often assist in the prevention of pests, diseases and disorders.


Monophlebidae is a family of scale insects commonly known as the giant scales or monophlebids. They occur in most parts of the world but more genera are found in the tropics than elsewhere.


Pittosporum ( or ) is a genus of about 200 species of flowering plants in the family Pittosporaceae. The genus is probably Gondwanan in origin; its present range extends from Australasia, Oceania, eastern Asia and some parts of Africa. Citriobatus can be included here, but might be a distinct (though closely related) genus. They are commonly known as pittosporums or, more ambiguously, "cheesewoods".

The species are trees and shrubs growing to 2–30 m tall. The leaves are spirally arranged or whorled, simple, with an entire or waved (rarely lobed) margin. The flowers are produced singly or in umbels or corymbs, each flower with five sepals and five petals; they are often sweetly scented. The fruit is a woody seed capsule, which bursts on ripening to release the numerous seeds. The seeds are coated with a sticky resinous substance. The genus is named after their sticky seeds, from the Greek meaning "pitch-seed".

Tarata (P. eugenioides) and kohuhu (P. tenuifolium) – both from New Zealand – and the Japanese cheesewood (P. tobira) from southern Japan are widely cultivated as ornamental plants in subtropical regions; pittosporums can also be grown indoors as bonsai. The petroleum nut (P. resiniferum) yields petroleum nut oil, which is sometimes proposed as biofuel; due to its excessive n-heptane content and consequent low octane rating, it is better suited as a source of n-heptane, which is otherwise produced from crude oil.

Many herbivores detest the resinuous pittosporums, in particular their seeds, which will stick anywhere. But some animals eat them with relish, for example the kea (Nestor notabilis), which likes P. anomalum fruit and seeds. The cottony cushion scale (Icerya purchasi) is a common pest on ornamental pittosporums (in particular the New Zealand species); the sac fungus Nectriella pironii often infects Japanese cheesewood.

Pittosporum tobira

Pittosporum tobira is a species of sweet-smelling flowering plant in the pittosporum family Pittosporaceae known by several common names, including Australian laurel, Japanese pittosporum, mock orange and Japanese cheesewood. It is native to eastern Mediterranean (Greece), as well as in Japan, China, and Korea, but it is used throughout the world as an ornamental plant in landscaping and as cut foliage.

It is an evergreen shrub which can reach 10 m (33 ft) tall by 3 m (10 ft) broad, and can become treelike. It can also be trimmed into a hedge. The leaves are oval in shape with edges that curl under and measure up to 10 cm (4 in) in length. They are leathery, hairless, and darker and shinier on the upper surfaces. The inflorescence is a cluster of fragrant flowers occurring at the ends of branches. The flower has five white petals each about a centimetre long. The fruit is a hairy, woody capsule about 1 cm wide divided into three valves. Inside are black seeds in a bed of resinous pulp.

The binomial qualifier tobira derives from the Japanese name for the plant.This shrub is a common, drought-tolerant and fairly hardy landscaping plant. Many cultivars have been developed, including dwarf forms and the popular 'Variegata', which has variegated leaves. It is used for hedges, living privacy screens, and indoor and outdoor planter boxes. The stems, leaves, and dried fruits are used in flower arrangements.The species and the cultivar 'Variegatum' have both gained the Royal Horticultural Society's Award of Garden Merit.Common pests of this plant include various aphids, mites, and leafhoppers, the cotton cushiony scale (Icerya purchasi), and root-knot nematodes (Meloidogyne spp.). It can be attacked by the pit-making pittosporum scale (Planchonia arabidis). It is vulnerable to the fungal plant pathogen Erythricium salmonicolor, which causes galls and the dieback disease known as pink limb blight.

Rodolia cardinalis

Rodolia cardinalis (common names vedalia beetle or cardinal ladybird) is a species of ladybird beetle that is sometimes described as endemic to Australia.[1]

Scale insect

The scale insects are small insects of the order Hemiptera, suborder Sternorrhyncha. They comprise the superfamily Coccoidea, previously placed in the now obsolete group called "Homoptera". There are about 8,000 described species of scale insects.

Trigonospila brevifacies

Trigonospila brevifacies is a species of true fly in the family Tachinidae native to eastern Australia. Like the vast majority of tachinid flies, T. brevifacies is a parasitoid of other insects, specifically late larval stages of a number of species of Lepidoptera. It is also known as the Australian Leaf-Roller Fly or Leafroller Fly.


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