Aleurocanthus woglumi
Encyclopedia
Aleurocanthus woglumi is a species of whitefly in the family Aleyrodidae. It is a pest of citrus
crops and is commonly known as the citrus blackfly because of its slate blue colour. It originated in Asia but has spread to other parts of the world. The parasitic
wasps, Encarsia perplexa
and Amitus hesperidum
can help control the pest.
, orange
and pomelo
that are most heavily infested. Non-citrus trees and shrubs when they grow by themselves are not normally attacked by this insect but they may be when they grow close to heavy infestations on citrus. In Hawaii, such trees as mango, avocado, pink tecoma and surinam cherry have hosted colonies.
in a spiral pattern on the undersides of leaves. The eggs are golden-brown but darken before hatching which happens in seven to ten days.
The nymph
moults three times. The first instar
is a brown, elongated oval shape, about 0.30 mm long with two transparent filaments curling back over the body. The second instar is a darker brown and has short spines on its body. It measures about 0.40 mm long. The third instar is glossy black with many stout spines and measures about 0.87 mm long by 0.74 mm wide. The larval stages last three to nine weeks.
The pupa
is ovate, black with short bristles and a marginal fringe of waxy secretion.
The adult when it first emerges has a pale yellow head, whitish legs and reddish-brown eyes. Soon afterwards it darkens, developing a fine covering of waxy powder which gives it a slate blue appearance. The wings are angled and held in a tented fashion. The whole life cycle takes from 45 to 130 days, depending largely on the temperature.
which deprives it of both water and nutrients. The excretion of honeydew
coats the leaf surfaces and encourages the growth of sooty mould fungus
. This can severely impair both leaf respiration
and photosynthesis
. The combination of all these factors causes a decline in the health and vigour of the tree and a reduction in fruit yield.
and Amitus hesperidum
. The former has a lower rate of reproduction than does A. hesperidum but is better able to search out suitable hosts. The latter is well synchronized with its host as adult female wasps are ready to lay their eggs at about the same time as suitable larval stages of the blackfly are present.These species have been used in biological control
of the pest. For example, both species were introduced into Hawaii in 1999 after discovery of the presence of the citrus blackfly the previous year. Both wasps have succeeded in establishing themselves and are helping to reduce the damage done by the pest.
The use of insecticide
s may help to control infestations temporarily but this is not advised because of the adverse effects on the environment and any existing predators. The application of an oil emulsion may be effective and less toxic. A sufficiency of water and appropriate applications of fertiliser will encourage growth and minimise damage.
Citrus
Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...
crops and is commonly known as the citrus blackfly because of its slate blue colour. It originated in Asia but has spread to other parts of the world. The parasitic
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
wasps, Encarsia perplexa
Encarsia perplexa
Encarsia perplexa is a tiny parasitic wasp, a parasitoid of the citrus blackfly, Aleurocanthus woglumi, which is a global pest of citrus trees. It was originally misidentified as Encarsia opulenta, but was recorded as a new species in 1998...
and Amitus hesperidum
Amitus hesperidum
Amitus hesperidum is a tiny parasitic wasp. It is a parasitoid of the citrus blackfly, Aleurocanthus woglumi, an important pest of citrus trees. It is a native of Asia but has been introduced to many other parts of the world as a means of controlling the citrus blackfly.-Distribution:This wasp is...
can help control the pest.
Distribution
This species is native to India but also occurs in other parts of Asia, Africa, Central and South America, Mexico, the West Indies, Jamaica and the United States (Florida, Texas and Hawaii).Host species
The citrus blackfly is found on over 300 host plants but it is citrus trees such as lemonLemon
The lemon is both a small evergreen tree native to Asia, and the tree's ellipsoidal yellow fruit. The fruit is used for culinary and non-culinary purposes throughout the world – primarily for its juice, though the pulp and rind are also used, mainly in cooking and baking...
, orange
Orange (fruit)
An orange—specifically, the sweet orange—is the citrus Citrus × sinensis and its fruit. It is the most commonly grown tree fruit in the world....
and pomelo
Pomelo
The pomelo is a citrus fruit native to Southeast Asia. It is usually pale green to yellow when ripe, with sweet white flesh and very thick albedo . It is the largest citrus fruit, 15–25 cm in diameter, and usually weighing 1–2 kg...
that are most heavily infested. Non-citrus trees and shrubs when they grow by themselves are not normally attacked by this insect but they may be when they grow close to heavy infestations on citrus. In Hawaii, such trees as mango, avocado, pink tecoma and surinam cherry have hosted colonies.
Life cycle
The female blackfly lays batches of eggsEgg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
in a spiral pattern on the undersides of leaves. The eggs are golden-brown but darken before hatching which happens in seven to ten days.
The nymph
Nymph (biology)
In biology, a nymph is the immature form of some invertebrates, particularly insects, which undergoes gradual metamorphosis before reaching its adult stage. Unlike a typical larva, a nymph's overall form already resembles that of the adult. In addition, while a nymph moults it never enters a...
moults three times. The first instar
Instar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
is a brown, elongated oval shape, about 0.30 mm long with two transparent filaments curling back over the body. The second instar is a darker brown and has short spines on its body. It measures about 0.40 mm long. The third instar is glossy black with many stout spines and measures about 0.87 mm long by 0.74 mm wide. The larval stages last three to nine weeks.
The pupa
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
is ovate, black with short bristles and a marginal fringe of waxy secretion.
The adult when it first emerges has a pale yellow head, whitish legs and reddish-brown eyes. Soon afterwards it darkens, developing a fine covering of waxy powder which gives it a slate blue appearance. The wings are angled and held in a tented fashion. The whole life cycle takes from 45 to 130 days, depending largely on the temperature.
Damage
The principal harm done by the citrus blackfly is the sucking of the tree's sapPlant sap
Sap is a fluid transported in xylem cells or phloem sieve tube elements of a plant. It transports water and nutrients throughout the plant....
which deprives it of both water and nutrients. The excretion of honeydew
Honeydew (secretion)
Honeydew is a sugar-rich sticky liquid, secreted by aphids and some scale insects as they feed on plant sap. When their mouthpart penetrates the phloem, the sugary, high-pressure liquid is forced out of the gut's terminal opening. Honeydew is particularly common as a secretion in the Hemipteran...
coats the leaf surfaces and encourages the growth of sooty mould fungus
Sooty mold
Sooty molds are Ascomycete fungi which grow on plant exudates and the sugary honeydew secreted by insects such as aphids, scales, the whitefly, and other insects which suck sap from their host plants. The name itself is descriptive, as sooty mold is a black, powdery coating adhering to the leaves...
. This can severely impair both leaf respiration
Cellular respiration
Cellular respiration is the set of the metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate , and then release waste products. The reactions involved in respiration are catabolic reactions that involve...
and photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
. The combination of all these factors causes a decline in the health and vigour of the tree and a reduction in fruit yield.
Management
The citrus blackfly has a number of natural enemies. The most effective agents for controlling it in Florida are the parasitic wasps, Encarsia perplexaEncarsia perplexa
Encarsia perplexa is a tiny parasitic wasp, a parasitoid of the citrus blackfly, Aleurocanthus woglumi, which is a global pest of citrus trees. It was originally misidentified as Encarsia opulenta, but was recorded as a new species in 1998...
and Amitus hesperidum
Amitus hesperidum
Amitus hesperidum is a tiny parasitic wasp. It is a parasitoid of the citrus blackfly, Aleurocanthus woglumi, an important pest of citrus trees. It is a native of Asia but has been introduced to many other parts of the world as a means of controlling the citrus blackfly.-Distribution:This wasp is...
. The former has a lower rate of reproduction than does A. hesperidum but is better able to search out suitable hosts. The latter is well synchronized with its host as adult female wasps are ready to lay their eggs at about the same time as suitable larval stages of the blackfly are present.These species have been used in biological control
Biological pest control
Biological control of pests in agriculture is a method of controlling pests that relies on predation, parasitism, herbivory, or other natural mechanisms...
of the pest. For example, both species were introduced into Hawaii in 1999 after discovery of the presence of the citrus blackfly the previous year. Both wasps have succeeded in establishing themselves and are helping to reduce the damage done by the pest.
The use of insecticide
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...
s may help to control infestations temporarily but this is not advised because of the adverse effects on the environment and any existing predators. The application of an oil emulsion may be effective and less toxic. A sufficiency of water and appropriate applications of fertiliser will encourage growth and minimise damage.