''Planococcus citri'', commonly known as the citrus mealybug, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of mealybugs native to

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...

. It has been introduced to the rest of the world, including

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...

, the

Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. Along with th ...

, and

Oceania Oceania (, , ) is a geographical region that includes Australasia, Melanesia, Micronesia, and Polynesia. Spanning the Eastern and Western hemispheres, Oceania is estimated to have a land area of and a population of around 44.5 million ...

, as an

agricultural pest A pest is any animal or plant harmful to humans or human concerns. The term is particularly used for creatures that damage crops, livestock, and forestry or cause a nuisance to people, especially in their homes. Humans have modified the environ ...

. It is associated with

citrus ''Citrus'' is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, lemons, grapefruits, pomelos, and limes. The genus ''Citrus'' is native to ...

, but it attacks a wide range of crop plants,

ornamental plant Ornamental plants or garden plants are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars that ...

s, and wild flora.Gill, H. K., et al
Citrus Mealybug, ''Planococcus citri'' (Risso) (Insecta: Hemiptera: Pseudococcidae).
EENY-537. Entomology and Nematology, Florida Cooperative Extension Service. University of Florida IFAS. Published 2012, revised 2013.

Description

Mealybugs are

sexually dimorphic Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

. The adult female citrus mealybug is about long with a white, brownish, or pinkKerns, D., et al
Citrus Mealybug (''Planococcus citri'').
Citrus Arthropod Pest Management in Arizona. University of Arizona Cooperative Extension, Tucson. body covered in white

wax Waxes are a diverse class of organic compounds that are lipophilic, malleable solids near ambient temperatures. They include higher alkanes and lipids, typically with melting points above about 40 °C (104 °F), melting to giv ...

. The edges of the body are lined with waxy filaments. It has a light gray longitudinal line down its back. Its legs and antennae are brown. The adult female lacks wings and resembles a

nymph A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label= Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are ...

. The adult male is slightly larger, has long wax filaments on the posterior end of the body, and has functional wings. In flight the male resembles a

gnat A gnat () is any of many species of tiny flying insects in the dipterid suborder Nematocera, especially those in the families Mycetophilidae, Anisopodidae and Sciaridae. They can be both biting and non-biting. Most often they fly in large ...

.Citrus Mealybug.
A Field Guide to Common Texas Insects. Texas A&M AgriLife Extension. The female deposits masses of eggs on plants. The masses, known as ovisacs, are covered in fluffy, cottony layers of wax filaments. The ovisac can contain up to 20 shiny yellowish, pink, or

amber Amber is fossilized tree resin that has been appreciated for its color and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects."Amber" (2004). In ...

von Ellenrieder, N
Citrus mealybug (''Planococcus citri'').
California Department of Food and Agriculture. 2003. eggs each about long. The first-

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...

nymph is called a crawler. It is yellowish with red eyes and has a wax coating. Crawlers are active and gregarious. The female nymph resembles the adult female, while the male nymph is longer and narrower. As they develop, the female nymph progresses through more instars than the male, and the male undergoes a pre-

pupa A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...

l stage.Goldasteh, S., et al. (2009)
Effect of temperature on life history and population growth parameters of ''Planococcus citri'' (Homoptera, Pseudococcidae) on coleus (''Solenostemon scutellarioides'' (L.) Codd.).
''Archives of Biological Sciences'' 61(2), 329-36. The male constructs a cottony cocoon for pupation, and the female does not. The citrus mealybug looks very similar to the vine mealybug (''Planococcus ficus''), and the two species are mainly distinguished by the arrangement of pores and tubular ducts on the tiny body of the female. This similarity can pose a problem in agriculture. For example, when growers are ready to attempt biological pest control of either mealybug, the use of molecular analysis is recommended to confirm the identity of the species so an appropriate parasitoid can be employed.Cavalieri, V., et al. (2008)
Identification of ''Planococcus ficus'' and ''Planococcus citri'' (Hemiptera: Pseudococcidae) by PCR-RFLP of COI gene.
''Zootaxa'' 1816, 65-68.

Taxonomy

''Planococcus citri'' was first described in 1813 by the Niçard naturalist

Antoine Risso Giuseppe Antonio Risso (8 April 1777 – 25 August 1845), called Antoine Risso, was a Niçard and natural history, naturalist. Risso was born in the city of Nice in the Duchy of Savoy, and studied under Giovanni Battista Balbis. He published ' (1 ...

. It belongs to the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

'' Planococcus'' in the mealybug

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Pseudococcidae. They are classified under the superfamily

Coccoidea Scale insects are small insects of the order Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme sexual dimorphism, they comprise the infraorder Coccomorpha which is considered a more convenient grouping than t ...

( scale insects) in the order Hemiptera (true bugs).

Biology

The longevity of the adult depends on temperature, but while females live for several weeks, males live fewer than three days in adult form. During this time, the male does not feed. It takes flight with its single pair of wings and seeks females. The female spends its longer lifetime feeding and producing eggs. Most other aspects of the life cycle depend on temperature, as well, including egg mortality, nymph mortality, rate of development,

sex ratio The sex ratio (or gender ratio) is usually defined as the ratio of males to females in a population. As explained by Fisher's principle, for evolutionary reasons this is typically about 1:1 in species which reproduce sexually. Many species d ...

fecundity Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to pr ...

, and the length of the egg-laying period. During mating, the citrus mealybug is known to engage in "triple

coitus Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetr ...

"; a female may copulate with two males at the same time, and a third male may at least make attempts to join the process. Males spend the one or two days of their adult lives mating, and have been observed achieving copulation with up to 23 females, with an average of about nine. There are usually several generations per year. The mealybug is most common in spring and summer, its populations fluctuating according to temperature and available host plants. Peak abundance is noted in early summer in

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

citrus. Mealybugs infesting plants in the constant conditions of greenhouses have stable, steadily reproducing populations all year. All mealybug species investigated so far have

endosymbiont An ''endosymbiont'' or ''endobiont'' is any organism that lives within the body or cells of another organism most often, though not always, in a mutualistic relationship. (The term endosymbiosis is from the Greek: ἔνδον ''endon'' "within ...

s:López-Madrigal, S., et al. (2013)
Mealybugs nested endosymbiosis: going into the 'matryoshka' system in ''Planococcus citri'' in depth.
''BMC Microbiology'' 13(1), 74. symbiotic

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...

that live inside their bodies and synthesize useful compounds such as

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...

s that the insect can utilize. Most mealybugs examined contain the betaproteobacterium '' Tremblaya princeps'' (''Candidatus Tremblaya princeps''). Other bacterial taxa have recently been found in mealybugs, as well. The citrus mealybug has a nested endosymbiosis. Its resident ''T. princeps'' contain their own endosymbionts, the gammaproteobacterium '' Moranella endobia'' (''Candidatus Moranella endobia'').Husnik, F., et al. (2013)
Horizontal gene transfer from diverse bacteria to an insect genome enables a tripartite nested mealybug symbiosis.
''Cell'' 153(7) 1567-78. This "

matryoshka Matryoshka dolls ( ; rus, матрёшка, p=mɐˈtrʲɵʂkə, a=Ru-матрёшка.ogg), also known as stacking dolls, nesting dolls, Russian tea dolls, or Russian dolls, are a set of wooden dolls of decreasing size placed one inside ano ...

" nested arrangement of a bacterium inside a bacterium inside an insect has been compared to the structure of a

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...

. ''T. princeps'' has almost no metabolic functions except for the production of amino acids, having lost the

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

s for most other life functions. It relies on ''M. endobia'' for energy, and is even unable to reproduce without it. ''T. princeps'' attracted attention when genetic analysis revealed that it has the smallest

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding g ...

of any bacterium studied thus far. At 139 kilo-base pairs, it has only about 120 genes, which helps to explain why it cannot function without its endosymbiont.

Impacts

The citrus mealybug can live "on almost any flowering plant". It is considered a citrus pest with a preference for grapefruit, but it has been found on plants from almost 70

families Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideal ...

.''Planococcus citri'' (Risso).
Scale Insects: Identification Tools for Species of Quarantine Significance. Systematic Entomology Laboratory, ARS, USDA. 2007. It is found on fruit, vegetable, and other food crops, including

pineapple The pineapple (''Ananas comosus'') is a tropical plant with an edible fruit; it is the most economically significant plant in the family Bromeliaceae. The pineapple is indigenous to South America, where it has been cultivated for many centuri ...

, sugar-apple, coconut,

muskmelon ''Cucumis melo'', also known as melon, is a species of '' Cucumis'' that has been developed into many cultivated varieties. The fruit is a pepo. The flesh is either sweet or bland, with or without a musky aroma, and the rind can be smooth (such a ...

, yam,

figs The fig is the edible fruit of ''Ficus carica'', a species of small tree in the flowering plant family Moraceae. Native to the Mediterranean and western Asia, it has been cultivated since ancient times and is now widely grown throughout the world ...

, strawberry, sweet potato, mangoes, bananas,

avocado The avocado (''Persea americana'') is a medium-sized, evergreen tree in the laurel family ( Lauraceae). It is native to the Americas and was first domesticated by Mesoamerican tribes more than 5,000 years ago. Then as now it was prized for ...

, date palm, common guava,

pomegranate The pomegranate (''Punica granatum'') is a fruit-bearing deciduous shrub in the family Lythraceae, subfamily Punicoideae, that grows between tall. The pomegranate was originally described throughout the Mediterranean Basin, Mediterranean re ...

common pear ''Pyrus communis'', the common pear, is a species of pear native to central and eastern Europe, and western Asia. It is one of the most important fruits of temperate regions, being the species from which most orchard pear cultivars grown in Euro ...

apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, where its wild ancestor, ' ...

, eggplant,

cacao tree ''Theobroma cacao'', also called the cacao tree and the cocoa tree, is a small ( tall) evergreen tree in the family Malvaceae. Its seeds, cocoa beans, are used to make chocolate liquor, cocoa solids, cocoa butter and chocolate. The largest pro ...

, and

soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu a ...

. It infests ornamental plants, including indoor plants, and it is common in greenhouses. It is found on ''

Amaryllis ''Amaryllis'' () is the only genus in the subtribe Amaryllidinae (tribe Amaryllideae). It is a small genus of flowering bulbs, with two species. The better known of the two, ''Amaryllis belladonna'', is a native of the Western Cape region of ...

'', ''

Begonia ''Begonia'' is a genus of perennial flowering plants in the family Begoniaceae. The genus contains more than 2,000 different plant species. The Begonias are native to moist subtropical and tropical climates. Some species are commonly grown ind ...

'', ''

Bougainvillea ''Bougainvillea'' ( , ) is a genus of thorny ornamental vines, bushes, and trees belonging to the four o' clock family, Nyctaginaceae. It is native to eastern South America, found from Brazil, west to Peru, and south to southern Argentina. ...

'', '' Canna'', ''

Cyclamen ''Cyclamen'' ( or ) is a genus of 23 species of perennial flowering plants in the family Primulaceae. ''Cyclamen'' species are native to Europe and the Mediterranean Basin east to the Caucasus and Iran, with one species in Somalia. They gro ...

'', '' Impatiens'', '' Narcissus'', '' Nicotiana'', cacti,

coleus ''Coleus'' is a genus of annual or perennial herbs or shrubs, sometimes succulent, sometimes with a fleshy or tuberous rootstock, found in the Old World tropics and subtropics. The relationship among the genera ''Coleus'', '' Solenostemon'' and ...

, croton,

sedges The Cyperaceae are a family of graminoid (grass-like), monocotyledonous flowering plants known as sedges. The family is large, with some 5,500 known species described in about 90 genera, the largest being the "true sedges" genus ''Carex'' wit ...

dahlia Dahlia (, ) is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico and Central America. A member of the Asteraceae (former name: Compositae) family of dicotyledonous plants, its garden relatives thus include the sunflower, ...

s, spurges, gardenias,

rose A rose is either a woody perennial flowering plant of the genus ''Rosa'' (), in the family Rosaceae (), or the flower it bears. There are over three hundred species and tens of thousands of cultivars. They form a group of plants that can be ...

s, and

tulip Tulips (''Tulipa'') are a genus of spring-blooming perennial herbaceous bulbiferous geophytes (having bulbs as storage organs). The flowers are usually large, showy and brightly coloured, generally red, pink, yellow, or white (usually in warm ...

s. Adult females and nymphs suck

sap Sap is a fluid transported in xylem cells (vessel elements or tracheids) or phloem sieve tube elements of a plant. These cells transport water and nutrients throughout the plant. Sap is distinct from latex, resin, or cell sap; it is a separ ...

with their piercing mouthparts. This leads to plant damage in the form of wilting and

chlorosis In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

of the foliage, leaf drop, stunted growth, and sometimes the death of the plant. Fruits such as

oranges An orange is a fruit of various citrus species in the family Rutaceae (see list of plants known as orange); it primarily refers to ''Citrus'' × ''sinensis'', which is also called sweet orange, to distinguish it from the related ''Citrus × ...

become lumpy and discolored when the insect feeds on them, and they may fall off the tree. Insects packed with harvested fruits continue to feed, causing more losses during shipping. The mealybug secretes honeydew, which coats leaves and fruits and causes the growth of sooty molds. A layer of mold can reduce the ability of a leaf to perform

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

, and makes fruit unmarketable. The citrus mealybug is also a

vector Vector most often refers to: *Euclidean vector, a quantity with a magnitude and a direction *Vector (epidemiology), an agent that carries and transmits an infectious pathogen into another living organism Vector may also refer to: Mathematic ...

for

plant virus Plant viruses are viruses that affect plants. Like all other viruses, plant viruses are obligate intracellular parasites that do not have the molecular machinery to replicate without a host. Plant viruses can be pathogenic to higher plants. ...

es.

Management

In agriculture, the insect can be managed with cultural, biological, and chemical control methods. Keeping orchard trees clipped so that they do not touch each other may help slow the spread. Cleaning farm equipment and other objects used in the field can help prevent its transport. Few insecticides are known to be very effective on mealybugs, because they can hide and avoid spraying, their wax layers resist some chemicals, and their overlapping generations prevent complete control. Insecticide treatment has two major problems: ''P. citri'' has developed resistance to some of them, and control of ''P. citri'' is heavily dependent on natural enemies whose numbers are reduced or eliminated by the same insecticides.

Chlorpyrifos Chlorpyrifos (CPS), also known as Chlorpyrifos ethyl, is an organophosphate pesticide that has been used on crops, animals, and buildings, and in other settings, to kill several pests, including insects and worms. It acts on the nervous systems ...

is commonly used, but in

Tunisia ) , image_map = Tunisia location (orthographic projection).svg , map_caption = Location of Tunisia in northern Africa , image_map2 = , capital = Tunis , largest_city = capital , ...

a high degree of resistance has developed, possibly due to repetitive use. In an attempt to forestall resistance, California commonly uses chlorpyrifos only during ''P. citri'' dormancy or as a postharvest treatment. (California's vineyards being in a similar climate to Tunisia, they are concerned about suffering a similar fate.) A variety of natural enemies exist. One survey in

Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Medit ...

noted 12 species of

parasitoid wasp Parasitoid wasps are a large group of hymenopteran superfamilies, with all but the wood wasps (Orussoidea) being in the wasp-waisted Apocrita. As parasitoids, they lay their eggs on or in the bodies of other arthropods, sooner or later causin ...

s on the citrus mealybug. It also recorded nine predatory insects, including ladybird beetles,

moth Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...

s, a

gall midge Cecidomyiidae is a family of flies known as gall midges or gall gnats. As the name implies, the larvae of most gall midges feed within plant tissue, creating abnormal plant growths called galls. Cecidomyiidae are very fragile small insects us ...

, and a

green lacewing Green lacewings are insects in the large family Chrysopidae of the order Neuroptera. There are about 85 genera and (differing between sources) 1,300–2,000 species in this widespread group. Members of the genera ''Chrysopa'' and ''Chrysoperla'' ...

. Agents of

biological 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 i ...

include a number of parasitoid wasps that attack the nymphs, including '' Leptomastidea abnormis'', '' Leptomastix dactylopii'', '' Chrysoplatycerus splendens'', and '' Anagyrus pseudococci''. Predators include the brown lacewing '' Sympherobius barberi'', the green lacewing '' Chrysopa lateralis'',

hoverfly Hover flies, also called flower flies or syrphid flies, make up the insect family Syrphidae. As their common name suggests, they are often seen hovering or nectaring at flowers; the adults of many species feed mainly on nectar and pollen, whil ...

larvae, and the scale-feeding snout-moth larva. The mealybug destroyer (''Cryptolaemus montrouzieri''), a ladybird beetle, readily attacks the citrus mealybug. Another option is a sticky trap baited with the

sex pheromone Sex pheromones are pheromones released by an organism to attract an individual of the same species, encourage them to mate with them, or perform some other function closely related with sexual reproduction. Sex pheromones specifically focus on ind ...

of the species to capture males. The pheromone has been isolated and synthesized, and is commercially available.Zada, A., et al. (2004)
Sex pheromone of the citrus mealybug ''Planococcus citri'': Synthesis and optimization of trap parameters.
''Journal of Economic Entomology'' 97(2), 361-68.

References

External links

''Planococcus citri''
on the UF / IFAS Featured Creatures website. * {{Authority control Hemiptera of Asia Pseudococcidae Agricultural pest insects Citrus pests Insects described in 1813 Taxa named by Antoine Risso