African citrus psyllid

Alert

Have you seen African citrus psyllid?

Be on the lookout and report signs to Biosecurity Queensland on 13 25 23 or contact the Exotic Plant Pest Hotline on 1800 084 881.

Early detection and reporting are key elements in controlling African citrus psyllid.

Like the Asian citrus psyllid (Diaphorina citri Kuwayama), the African citrus psyllid (Trioza erytreae del Guercio) is a sap-sucking insect that can transmit one of the world's most serious bacterial diseases of citrus, huanglongbing, otherwise known as citrus greening disease. The African citrus psyllid can transmit the Asian and African strains of the bacterium.

While the insect itself is a minor pest of citrus, huanglongbing is a serious threat to citrus-producing areas worldwide.

African citrus psyllid, Asian citrus psyllid and huanglongbing are not known to occur in Australia.

Other names

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

Description

Adults

  • Small, about 4mm long.
  • Males are smaller than females.
  • Abdomen is brown-grey, lighter underneath; the head is black.
  • Males have an abdomen that ends in a blunt tip; the female's abdomen ends in a sharp point.
  • Forewings are large and transparent with clearly defined veins.
  • Adults have a distinctive feeding posture, with their heads angled down, almost touching the plant surface, and the body lifted at 35 degree angle.

Nymphs

  • Tiny (0.3–1.6mm long). There are 5 nymphal instars.
  • Flat with a distinct marginal fringe of white, waxy filaments. Their body colour varies from yellow, olive-green to dark grey.
  • On their fifth instar, 2 pale brown spots appear on the abdomen.
  • Mainly found on new flushing citrus growth.
  • Largely sedentary (don't move much) and can form noticeable colonies on the underside of new leaves, sometimes moving to the upper leaf surface if populations are high and overcrowded.

Eggs

  • Tiny, yellow or orange, cylindrical, and have an upturned, sharp point.
  • Each egg has a short stalk, which is inserted into the plant.
  • 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

  • Found mostly in 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. 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

Common sap sucking insects such as citrus leaf miner and aphids can also cause leaf distortion and sooty mould to develop. If you find leaf distortion and sooty mould, look for the insect causing the damage. Psyllids are active insects, and will jump if disturbed. African citrus psyllid nymphs could be confused with soft scale insects.

The feeding posture of an adult African citrus psyllid is distinctive, with its head down, almost touching the leaf, and the rest of its body raised at a 35 degree angle.

If you suspect African citrus psyllid, don't hesitate to report it.

Distribution

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 (i.e. Madagascar, Mauritius and Reunion) and Atlantic (i.e. Helena, Madeira, Porto Santo, Tenerife and Gomera) oceans.

Hosts

The preferred host of African citrus psyllid is white ironwood (Vepris lanceolata), however all citrus cultivars are also hosts (e.g. 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

  • Mated females may lay 217–1,305 eggs.
  • Females prefer to lay their eggs on leaf margins and along the midribs of young, tender, actively growing foliage.
  • The eggs hatch in 6–15 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 17–43 days, depending on many factors including temperature.
  • From the fifth instar stage, the nymph changes into a winged adult.
  • There is no pupal stage.
  • Adults live 17–50 days depending on season (shorter in summer, longer in winter).

Impacts

Citrus is an important crop in Australia, with over 28,000 hectares of citrus planted, and around 1,900 growers (source: Citrus Australia). For the year ending June 2017, citrus production was valued at $724.4 million.

African citrus psyllid is considered to be a minor pest on its own. Overseas, when populations of African citrus psyllid are high, the psyllid can cause severe leaf distortion and pits in the leaf surface. Sooty mould growth (resulting from excess honeydew production) can also affect the plants ability to photosynthesize, which can affect overall plant health. Production costs can increase as a result of the need to control the pest and market access can be disrupted. In Australia, the nursery industry would also be affected.

The economic impact of the African citrus psyllid would be significantly increased if the serious citrus disease huanglongbing was also present. Huanglongbing, causes citrus tree death and is readily spread by the African citrus psyllid.

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

How it is spread

Adult African citrus psyllids are generally short distance fliers, covering at least 1.5km when seeking new hosts. Strong winds or cyclones could cause them to spread further.

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

Like the Asian citrus psyllid, 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.
  • Look closely at host plants with a white dusting of excreted honeydew pellets to identify the cause. The psyllids excrete pellets of honeydew that look like tiny, white eggs. The ground or vegetation under a badly infested tree can look like it has been dusted with white powder (the excreted pellets).
  • If detected look for adult psyllids, nymphs and eggs, especially in spring.
  • While adults can be found all year round, eggs and nymphs will only be found when plants are actively flushing and producing new growth.

Report suspected African citrus psyllid to Biosecurity Queensland immediately on 13 25 23 or contact the Exotic Plant Pest Hotline on 1800 084 881.

Legal requirements

African citrus psyllid is a prohibited plant pest under the Biosecurity Act 2014.

Report suspected African citrus psyllid to Biosecurity Queensland immediately on 13 25 23 or contact the Exotic Plant Pest Hotline on 1800 084 881.

If you think you have found African citrus psyllid, you must take all reasonable and practical steps under your control to minimise any associated risks. This is called a general biosecurity obligation (GBO).

Further information