''Trioza erytreae'', the African citrus psyllid, is a sap-sucking insect, a

hemiptera Hemiptera (; ) is an order of insects, commonly called true bugs, comprising more than 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, assassin bugs, bed bugs, and shield bugs. They range in size from ...

n bug in the family

Triozidae Triozidae is one of seven families, collectively referred to as Psylloidea, plant lice, based on the type genus ''Trioza''. They had traditionally been considered part of a single family, Psyllidae, but recent classifications divide the superfam ...

. It is an important pest of

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

, being one of only two known vectors of the serious citrus disease, '' huanglongbing'' or citrus greening disease. It is widely distributed in Africa. The other vector is the Asian citrus psyllid, '' Diaphorina citri''.EPPO

Distribution

The citrus psyllid is found in Cameroon, Comoros, the Congo, Eswatini, Ethiopia, Kenya, Madagascar, Malawi, Mauritius, Réunion, Rwanda, South Africa, St. Helena, Sudan, Tanzania, Uganda, Zambia, and Zimbabwe. It is also found in Saudi Arabia, Yemen, and the Macaronesian archipelagos of Madeira and the Canary islands. It is sensitive to hot, dry conditions and favours cool, moist areas 500 m above sea level. Recently it has been introduced into Spain through Galicia and Portugal. However, huanglongbing (citrus greening disease) has not been detected yet in these countries.

Description

The adult psyllid is at first pale, but darkens later to a light-brown colour. The female is larger than the male and has a sharply pointed abdomen as compared to the male's blunt one. It typically adopts a distinctive stance when feeding, with head down sucking sap and body raised at an angle of about 35°.

Lifecycle

''Trioza erytreae'' is confined to host plants in the family

Rutaceae The Rutaceae () is a family (biology), family, commonly known as the rueRUTACEAE
in Bo ...

. It occurs on wild plants such as horsewood and white ironwood, as well as on citrus, especially

lemon The lemon (''Citrus'' × ''limon'') is a species of small evergreen tree in the ''Citrus'' genus of the flowering plant family Rutaceae. A true lemon is a hybrid of the citron and the bitter orange. Its origins are uncertain, but some ...

s and

lime Lime most commonly refers to: * Lime (fruit), a green citrus fruit * Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide * Lime (color), a color between yellow and green Lime may also refer to: Bo ...

s. A female psyllid can lay up to 2000

eggs An egg is an organic vessel in which an embryo begins to develop. Egg, EGG or eggs may also refer to: Biology * Egg cell, the female reproductive cell (gamete) in oogamous organisms Food * Eggs as food Places * Egg, Austria * Egg, Switzerland ...

over the course of a four- to seven-week period. Eggs are laid on the margins of new leaf growth and are anchored by short stalks. They hatch after 7 to 14 days, and the first-

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

nymphs A nymph (; ; sometimes spelled nymphe) is a minor female nature deity in ancient Greek folklore. Distinct from other Greek goddesses, nymphs are generally regarded as personifications of nature; they are typically tied to a specific place, land ...

start to feed on the underside of the leaves where they begin to form

gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants. Plant galls are abnormal outgrowths of plant tissues, similar to benign tumors or war ...

s. The feeding of a large number of nymphs causes curling of the leaves, distortion of shoots, and even cessation of growth. The nymphs moult five times before becoming winged adults. The nymphal development stage lasts between 20 and 40 days depending on temperature.

Damage and control

''Trioza erytreae'' is one of only two vectors of the causative agents of citrus greening disease, the

phloem Phloem (, ) is the living tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This transport process is ...

-restricted,

Gram-negative Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists ...

bacterium ''Candidatus'' Liberibacter spp. The Asian form, ''L. asiaticus'', is heat tolerant and symptoms of the disease can develop at temperatures up to 35 °C. The African form, ''L. africanum,'' is heat sensitive and symptoms only develop when the temperature is in the range 20–25 °C. Although ''T. erytreae'' is the natural vector of African citrus greening and ''D. citri'' the natural vector of Asian citrus greening, either psyllid can in fact transmit either of the greening agents under experimental conditions. Associated with ''T. erytreae'' in Zimbabwe are two primary

parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...

s and a number of secondary and tertiary hyperparasitoids. One of the primary parasitoids, '' Tetrastichus radiatus'', remains external to the psyllid host, whereas the other, '' Psyllaephagus pulvinatus'', is an internal parasitoid. The major secondary hyperparasitoid is '' Aphidencyrtus cassatus'', which was recorded in large numbers and which attacks both of the primary parasitoids.

References

{{Taxonbar, from=Q7843174 Triozidae Agricultural pest insects Hemiptera of Africa Hemiptera of Asia Hemiptera of Europe Insects described in 1918