Planococcus citri | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Insecta |
Order: | Hemiptera |
Suborder: | Sternorrhyncha |
Family: | Pseudococcidae |
Genus: | Planococcus |
Species: | P. citri |
Binomial name | |
Planococcus citri Risso, 1813 | |
Planococcus citri, commonly known as the citrus mealybug, is a species of mealybugs native to Asia. It has been introduced to the rest of the world, including Europe, the Americas, and Oceania, as an agricultural pest. It is associated with citrus, but it attacks a wide range of crop plants, ornamental plants, and wild flora. [1]
Mealybugs are sexually dimorphic. The adult female citrus mealybug is about 3 mm (0.12 in) long with a white, brownish, [1] or pink [2] body covered in white wax. 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. The adult male is slightly larger, has long wax filaments on the posterior end of the body, and has functional wings. [1] In flight the male resembles a gnat. [2] [3]
The female deposits masses of eggs on plants. The masses, known as ovisacs, are covered in fluffy, cottony layers of wax filaments. [1] [3] The ovisac can contain up to 20 shiny yellowish, [1] pink, [2] or amber [4] eggs each about 0.3 mm (0.012 in) long. The first-instar nymph is called a crawler. It is yellowish with red eyes and has a wax coating. [1] Crawlers are active and gregarious. [2] The female nymph resembles the adult female, while the male nymph is longer and narrower. [1] As they develop, the female nymph progresses through more instars than the male, and the male undergoes a pre-pupal stage. [1] [5] The male constructs a cottony cocoon for pupation, and the female does not. [1]
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. [6]
Planococcus citri was first described in 1813 by the Niçard naturalist Antoine Risso. It belongs to the genus Planococcus in the mealybug family Pseudococcidae. They are classified under the superfamily Coccoidea (scale insects) in the order Hemiptera (true bugs). [1]
The longevity of the adult depends on temperature, but while females live for several weeks, males live fewer than three days in adult form. [5] During this time, the male does not feed. [1] It takes flight with its single pair of wings and seeks females. [3] 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, fecundity, and the length of the egg-laying period. [5]
During mating, the citrus mealybug is known to engage in "triple coitus"; 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. [7]
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 citrus. Mealybugs infesting plants in the constant conditions of greenhouses have stable, steadily reproducing populations all year. [1]
All mealybug species investigated so far have endosymbionts: [8] symbiotic bacteria that live inside their bodies and synthesize useful compounds such as amino acids 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). [8] [9] This "matryoshka" nested arrangement of a bacterium inside a bacterium inside an insect has been compared to the structure of a cell. [8] T. princeps has almost no metabolic functions except for the production of amino acids, having lost the genes for most other life functions. It relies on M. endobia for energy, and is even unable to reproduce without it. [8] T. princeps attracted attention when genetic analysis revealed that it has the smallest genome 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. [9]
The citrus mealybug can live "on almost any flowering plant". [4] It is considered a citrus pest with a preference for grapefruit, [1] but it has been found on plants from almost 70 families. [10] It is found on fruit, vegetable, and other food crops, including pineapple, sugar-apple, coconut, melon, yam, figs, strawberry, sweet potato, mangoes, bananas, avocado, date palm, common guava, pomegranate, common pear, apple, eggplant, cacao tree, and soybean. It infests ornamental plants, including indoor plants, and it is common in greenhouses. It is found on Amaryllis , Begonia , Bougainvillea , Canna , Cyclamen , Impatiens , Narcissus , Nicotiana , cacti, coleus, croton, sedges, dahlias, spurges, gardenias, roses, and tulips. [1]
Adult females and nymphs suck sap with their piercing mouthparts. [5] This leads to plant damage in the form of wilting and chlorosis of the foliage, leaf drop, stunted growth, and sometimes the death of the plant. Fruits such as oranges 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, and makes fruit unmarketable. [1] The citrus mealybug is also a vector for plant viruses. [5]
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. [2] 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. [11]
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 is commonly used, but in Tunisia 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.) [12]
A variety of natural enemies exist. One survey in Egypt noted 12 species of parasitoid wasps on the citrus mealybug. It also recorded nine predatory insects, including ladybird beetles, moths, a gall midge, and a green lacewing. [13]
Agents of biological control 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 larvae, and the scale-feeding snout-moth larva. [1] The mealybug destroyer (Cryptolaemus montrouzieri), a ladybird beetle, readily attacks the citrus mealybug. [2]
Another option is a sticky trap baited with the sex pheromone of the species to capture males. The pheromone has been isolated and synthesized, and is commercially available. [2] [14]
Whiteflies are Hemipterans that typically feed on the undersides of plant leaves. They comprise the family Aleyrodidae, the only family in the superfamily Aleyrodoidea. More than 1550 species have been described.
Psyllidae, the jumping plant lice or psyllids, are a family of small plant-feeding insects that tend to be very host-specific, i.e. each plant-louse species only feeds on one plant species (monophagous) or feeds on a few closely related plants (oligophagous). Together with aphids, phylloxerans, scale insects and whiteflies, they form the group called Sternorrhyncha, which is considered to be the most "primitive" group within the true bugs (Hemiptera). They have traditionally been considered a single family, Psyllidae, but recent classifications divide the group into a total of seven families; the present restricted definition still includes more than 70 genera in the Psyllidae. Psyllid fossils have been found from the Early Permian before the flowering plants evolved. The explosive diversification of the flowering plants in the Cretaceous was paralleled by a massive diversification of associated insects, and many of the morphological and metabolic characters that the flowering plants exhibit may have evolved as defenses against herbivorous insects.
Mealybugs are insects in the family Pseudococcidae, unarmored scale insects found in moist, warm habitats. Of the more than 2000 described species, many are considered pests as they feed on plant juices of greenhouse plants, house plants and subtropical trees and also act as a vector for several plant diseases. Some ants live in symbiotic relationships with them, protecting them from predators and feeding off the honeydew which they excrete.
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 the superfamily Coccoidea due to taxonomic uncertainties. Adult females typically have soft bodies and no limbs, and are concealed underneath domed scales, extruding quantities of wax for protection. Some species are hermaphroditic, with a combined ovotestis instead of separate ovaries and testes. Males, in the species where they occur, have legs and sometimes wings, and resemble small flies. Scale insects are herbivores, piercing plant tissues with their mouthparts and remaining in one place, feeding on sap. The excess fluid they imbibe is secreted as honeydew on which sooty mold tends to grow. The insects often have a mutualistic relationship with ants, which feed on the honeydew and protect them from predators. There are about 8,000 described species.
Maconellicoccus hirsutus, is a pest of many plants, trees, and shrubs. It infests hibiscus, citrus, coffee, sugar cane, annonas, plums, guava, mango, okra, sorrel, teak, mora, pigeon pea, peanut, grapevine, maize, asparagus, chrysanthemum, beans, cotton, soybean, cocoa, and many other plants. The pest forms colonies on the host plant, and if left undisturbed, the colonies will grow into large masses of white waxy coverings on branches, fruiting structures, leaves, and even whole plants, including large trees.
The harlequin cabbage bug, also known as calico bug, fire bug or harlequin bug, is a black stinkbug of the family Pentatomidae, brilliantly marked with red, orange, yellow and white markings. It is a major pest of cabbage and related crops in the Brassicaceae, as well as the ornamental flower cleome throughout tropical and North America, especially the warmer parts of the United States. Nymphs are active during the summer and in the tropics the bug can achieve three to six generations a year. In the northern range there is only one generation annually and the insects overwinter as adults in crop residues or field edges. Organic control involves hand-picking the insects off the plants and being especially careful to remove and destroy all the eggs, which are black-and-white striped, laid in clutches of twelve.
Pseudococcus viburni is a close relative of the grape mealybug and a pest of the vineyards around the world.
Aphis gossypii is a tiny insect, an aphid ("greenfly") in the superfamily Aphidoidea in the order Hemiptera. It is a true bug and sucks sap from plants. It is a widely distributed pest of a variety of agricultural crops in the families Cucurbitaceae, Rutaceae and Malvaceae. Common names include cotton aphid, melon aphid and melon and cotton aphid.
Diaphorina citri, the Asian citrus psyllid, is a sap-sucking, hemipteran bug in the family Psyllidae. It is one of two confirmed vectors of citrus greening disease. It has a wide distribution in southern Asia and has spread to other citrus growing regions.
Putoidae is a family of scale insects commonly known as giant mealybugs or putoids. There is probably a single genus, Puto, containing about sixty species. The genus name Macrocerococcus has also been used but it is now considered to be a synonym of Puto. The genus Puto was formerly classified as a member of the Pseudococcidae; however, it so significantly differed from the rest of the Pseudococcidae that it was accorded its own family Putoidae.
Paracoccus marginatus, commonly known as the papaya mealybug, is a small sap-sucking insect in the mealybug family, Pseudococcidae. It is found on a number of different hosts, including economically important tropical fruit trees and various ornamental plants.
Phenacoccus manihoti is a mealybug insect species.
Tamarixia radiata, the Asian citrus cyllid parasitoid, is an hymenopteran wasp from the family Eulophidae which was discovered in the 1920s in the area of northwestern India (Punjab), now Pakistan. It is a parasitoid of the Asian citrus psyllid, an economically important pest of citrus crops around the world and a vector for Citrus greening disease.
Balanococcus cordylinidis, the cabbage tree mealybug, is a species of insect in the family Pseudococcidae.
Phenacoccus solenopsis, the cotton mealybug or solenopsis mealybug, is a species of mealybug in the family Pseudococcidae. Having originated in North America, it has spread to other parts of the world and become a major pest of cotton crops.
Geococcus coffeae is a species in the mealybug family, Pseudococcidae, commonly known as the coffee root mealybug, or brown scale. It lives underground where it inserts its mouthparts into roots and sucks the sap.
Planococcus is a genus of true bugs belonging to the family Pseudococcidae. The genus has a cosmopolitan distribution. A number of species are invasive agricultural pests.
Pseudococcus comstocki, common name Comstock mealybug, is a species of mealybug. The species was first discovered in 1902 in Japan. It is an invasive pest species that feeds on fruit and plants.
Planococcus ficus, commonly known as the vine mealybug, is a species of mealybug, belonging to the family Pseudococcidae, native to tropical and subtropical regions. The vine mealybug is found in Europe, Northern Africa, Southern Africa, the Americas, and the Middle East. The vine mealybug is invasive to weedy plants in many different regions of the world.
Orchamoplatus citri, commonly known as the Australian citrus whitefly, is a whitefly species in the genus Orchamoplatus. It is found across Australia and New Zealand, primarily foraging on the leaves of citrus trees.
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