African citrus psyllid

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Scientific name

Trioza erytreae

Other names

• Two-spotted citrus psyllid
• African citrus psylla
• Citrus psylla
• Citrus psyllid

Description

Adults

• Adults are small (3–4mm long).
• Abdomens are brown-grey, lighter underneath. Heads are black.
• Forewings are large and transparent with clearly defined veins.
• Feeding posture is distinctive, with head angled down (almost touching the plant surface) and body lifted at an angle of about 35°.

Nymphs

• There are 5 tiny nymphal instars ranging from 0.3mm to 1.6mm long.
• Nymphs are flat with a distinct marginal fringe of white waxy filaments.
• Body colour varies from yellow to olive green to dark grey.
• On their fifth instar, 2 pale brown spots appear on the abdomen.
• Nymphs are mainly found on the underside of young leaves, forming distinctive cup-shaped open galls.

Eggs

• Eggs are tiny, yellow-orange and cylindrical. They have an upturned sharp point at the anterior.
• Each egg has a short stalk, which is inserted into the plant.
• Eggs are laid on leaf margins and along the midribs of young, tender, actively growing flush, and occasionally on flower buds and on young fruit.

Plant stage and plant parts affected

• Psyllids are found mostly on young flushing leaves and shoots of host plants.

Plant damage

• As nymphs feed, they cause distinctive cup-shaped or pit-like galls to form in the lower leaf surface, particularly in immature leaves. These are often visible as bumps in the upper leaf surface. The galls remain in the leaves when the psyllids leave the plant and when the twigs/leaves become mature.
• Feeding can also cause leaf distortion, curling, stunting and leaf yellowing.
• High pest populations can cause leaf drop and shoot-tip death.

May be confused with

• Adults may be confused with citrus leaf miner and common sap-sucking insects such as winged aphids. If you find leaf distortion and sooty mould, look for the insect causing the damage. Psyllids are active insects and will jump if disturbed.
• Nymphs could be confused with soft scale insects or mealybugs.

Distribution

African citrus psyllid prefers cooler, moist climates. It is very sensitive to extremes of hot, dry weather.
It occurs in sub-Saharan Africa, Saudi Arabia and Yemen, plus numerous islands of the Indian Ocean (such as Madagascar, Mauritius and Reunion) and the Atlantic Ocean (such as Helena, Madeira, Porto Santo, Tenerife and Gomera). It has also been reported in parts of Europe.

Hosts

The preferred host of African citrus psyllid is white ironwood (Vepris lanceolata). However, hosts include all citrus cultivars (such as orange, lemon, lime, grapefruit, mandarin, kumquat, tangelo, pomelo, native citrus and citrus rootstock).

Other hosts include:

• native and exotic mock orange/orange jasmine (Murraya spp.)
• lime berry (Triphasia trifolia) and horsewood (Clausena anisata)
• orange-climber or forest-pepper (Toddalia asiatica)
• small knobwood (Zanthoxylum capense).

Life cycle

• A mated female may lay up to 2000 eggs.
• Females prefer to lay their eggs on leaf margins and along the midribs of young, tender, actively growing foliage.
• The eggs hatch in 5–17 days.
• The eggs hatch into wingless nymphs, which move to the lower leaf surface to feed.
• The nymphs moult 4 times, gradually getting bigger each moult as they transition through the 5 nymphal stages (instars). This process can take 17–47 days, depending on many factors including temperature.
• From the fifth instar stage, the nymph changes into a winged adult.
• Adults live 17–50 days, depending on the season (shorter in summer, longer in winter).

Impacts

Citrus is an important crop in Australia—there are about 33,000 hectares of commercial citrus orchard (Source: Citrus Australia, Australian citrus tree census 2024 (PDF, 1.7MB)). Citrus production for the 2024–25 financial year was valued at $1,234.8 million, with Queensland the second-largest producer (Source: Hort Innovation | Australian horticulture statistics handbook 2024/25).

African citrus psyllid is less aggressive than Asian citrus psyllid, and is considered a minor pest on its own. However, the economic impact of the African citrus psyllid would be significantly increased if the serious citrus disease huanglongbing was also present. Once a tree is infected with huanglongbing, there is no cure except for removal of infected trees and chemical control of the vectors.

Home gardeners can also be affected as citrus is a common backyard plant.

How it is spread

Adults can fly for at least 1.5km when seeking new hosts, infesting a large area in a relatively short time. Strong winds or cyclones could cause them to spread further.

Movement of infested plant material (such as budwood, grafted trees, rootstock and seedlings) can spread the pests over much larger distances.

Like the Asian citrus psyllid, the African citrus psyllid and huanglongbing could be introduced into Australia through the illegal importation of infested plant material.

The Australian Government closely regulates approved imports of plant material and monitors for illegal plant movement.

Monitoring and action

Regularly monitor common host plants, such as citrus.

• Inspect new flushing growth for leaf distortion, leaf pitting and excessive honeydew production resulting in sooty mould.
• Closely monitor plants during the citrus flushing season for nymphs, adults and eggs.

Report suspected African citrus psyllid using 1 of these methods:

• Report online.
• Phone Biosecurity Queensland on 13 25 23.
• Phone the Exotic Plant Pest Hotline on 1800 084 881.

Prevention

Use these resources to help protect your farm from plant pests and diseases:

• Protecting your farm from plant pests and diseases
• My property biosecurity
• Farm biosecurity
• Biosecurity manual for citrus producers (PDF, 4MB).

Legal requirements

African citrus psyllid is not present in Queensland and is considered biosecurity matter under the Biosecurity Act 2014.

If you think you have found African citrus psyllid, you must report it using 1 of these methods:

• Report online.
• Phone Biosecurity Queensland on 13 25 23.
• Phone the Exotic Plant Pest Hotline on 1800 084 881.

You must also take all reasonable and practical steps that are under your control to minimise any associated risks. This is part of your general biosecurity obligation.

Further information

• To learn how to protect your orchard, read the Biosecurity manual for citrus producers (PDF, 4MB).
• To understand more about citrus industry biosecurity planning, check the Biosecurity plan for the citrus industry (PDF, 4MB).
• Be part of the CitrusWatch program.
• Find out more from the Threat specific contingency plan: huanglongbing and its vectors (PHA, 2015) (PDF, 2.7MB).