Asian citrus psyllid

Have you seen Asian citrus psyllid?

In Queensland, the Asian citrus psyllid is prohibited matter under the Biosecurity Act 2014.

Be on the lookout for this pest and immediately report them to Biosecurity Queensland. Do not move any plant material off your property as this can spread the pest.

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General information

Like the African citrus psyllid, the Asiancitrus psyllid (Diaphorina citri Kuwayama) is a sap-sucking insect that can transmit the lethal citrus disease, huanglongbing, also known as 'citrus greening'.

While the insect itself is not known to be a major citrus pest, huanglongbing is a serious threat to citrus-producing areas worldwide. The Asian citrus psyllid, African citrus psyllid and huanglongbing are not found in Australia.

Overview

Symptoms

In the Americas, high numbers of nymphs distort the growth of leaves and stems and may cause death of new growth. Notching of leaves may also occur. These symptoms are not common in Asia.

The honeydew produced by Asian citrus psyllid can lead to sooty mould growth on plants.

Appearance

Adults

  • Adults are small (3-4mm long), brownish, sap-sucking insects.
  • The forewings are distinctively patterned with mottled brown patches.
  • The abdomen has a pointed shape when viewed from above.
  • Adults have a distinctive feeding posture, with the head down, almost touching the plant surface, and the body lifted at 45o.


Nymphs

  • Nymphs are dull orange with red eyes.
  • They can secrete white, string-like honeydew that may melt to form droplets at temperatures above 36oC. 
  • They can be difficult to see because they are small, flat, and close to the surface of twigs and leaves.
  • They are mainly found on buds, leaves and stems of young flushing growth less than 50mm long.


Eggs

  • Eggs are bright yellow-orange and almond-shaped.
  • They are laid in groups on buds and young flush tips less than 10mm long
DistributionAsian citrus psyllid occurs throughout Asia, and in parts of North, South and Central America, and some islands off Africa. Closer to Australia, it is found in Indonesia (including Papua), East Timor and north-western Papua New Guinea. The psyllid was detected near Darwin in 1915, but was eradicated along with an incursion of citrus canker. There have been no detections of the psyllid in Australia since then.
Lifecycle

Female of D. citri lays eggs on petioles, axillary buds, upper and lower surfaces of young leaves and tender stems. The average incubation period of eggs is 4 days. The eggs then hatch and pass through 5 nymphal instars. First- and second-instar nymphs mostly aggregate and feed inside the folded leaves. Young nymphs are quite docile and move only when disturbed or over-crowded. The nymphs continuously secrete copious amounts of honeydew from the anus and a thread-like waxy substance from the circumanal glands resulting in the growth of black sooty mould on the lower leaves.

The complete life cycle takes 14-48 days, depending on environmental factors such as temperature and season. There is no diapause, but populations are typically low in winter or during dry periods. There are 9-10 generations a year, with up to 16 observed in field cages. Population fluctuations are closely correlated with flushing rhythm of citrus trees, as eggs are laid exclusively on young flush points.

Crops affectedOrange, grapefruit, mandarin, tangelo, lemon, lime, kumquat, pomelo, trifoliate orange, native citrus
Hosts

All citrus cultivars are hosts of the psyllid (e.g. orange, grapefruit, mandarin, tangelo, lemon, lime, kumquat, pomelo, trifoliate orange and native citrus species). Some species and varieties are better hosts than others. Murraya spp. (native and ornamental forms of mock orange/orange jasmine) and Bergera koenigii (curry leaf) are also favoured hosts.

Asian citrus psyllid can also feed on:

  • Afraegle spp. (Gabon powder-flask, Nigerian powder-flask)
  • Atalantia buxifolia (Chinese box-orange)
  • Balsamocitrus dawei (Uganda powder-flask)
  • Citropsis spp. (west African cherry-orange, Gillet's cherry- orange)
  • Limonia acidissima (wood apple, elephant apple)
  • Merrillia caloxylon (Malay lemon)
  • Naringi crenulata (hesperethusa)
  • Pamburus missionis
  • Swinglea glutinosa (tabog)
  • Triphasia trifolia (lime berry)
  • Clausena spp. (e.g. wampee),
  • Toddalia asiatica (orange-climber, forest pepper)
  • Vepris lanceolata (white ironwood).
Spread of pest

Asian citrus psyllid occurs throughout Asia, and in parts of North, South and Central America, and some islands off Africa. Closer to Australia, it is found in Indonesia (including Papua), East Timor and north-western Papua New Guinea. The psyllid was detected near Darwin in 1915, but eradicated during eradication of an incursion of citrus canker. There have been no detections of the psyllid in Australia since then.

Long distance spread most commonly occurs via the movement of plant material infested with the psyllids. Ornamentals and food plants such as mock orange/ orange jasmine (Murraya) and curry leaf (Bergera koenigii), respectively, have been known to spread psyllids. Tropical storms and cyclones may also lead to long distance spread.

Asian citrus psyllid and huanglongbing could be introduced into Australia through the illegal importation of host plants, leaves such as kaffir lime leaves or curry leaves for cooking, or budwood. The Australian Quarantine and Inspection Service (AQIS) closely regulates approved imports of plant material and monitors for illegal plant movement.

Management and quarantine

Regularly monitor common host plants, such as citrus, Murraya spp. and curry leaf:

  • Inspect new flushing growth (from 5-50 mm long) for adults, nymphs and eggs, particularly in spring, within 14 days of flower buds opening.
  • While adults can be found all year round, eggs and nymphs will only be found when plants are producing new flushing growth.
  • Eggs will often be nestled in crevices of unfolded leaves.
  • Look for the cause of sooty mould or honeydew on plants.
  • Look for the cause of leaf distortion or brown shrivelled shoot tips.
  • Look for adults on mature leaves, especially the underside of leaves in between flush events, particularly in regions with distinct winters.

There are simple steps you can take to protect your farm:

  • To avoid introducing Asian citrus psyllid onto your property, establish new plantings with reputable pest-free and disease-free nursery stock. On receipt of any new plants, check that they are free from pest and disease. If Asian citrus psyllid is detected, isolate the nursery stock from healthy plants until official checks are completed.
  • Do not illegally import plant material from overseas.
  • Make sure that you and your farm workers are familiar with all life cycle stages of the psyllid, its characteristic honeydew, and deformed flush growth. Regularly check your orchard and report any unusual or unfamiliar symptoms. Be conscious that the psyllid can transmit the lethal citrus disease, huanglongbing.
Reference and acknowledgement

Asian citrus psyllid fact sheet (PDF, 297.7KB)

Andrew Beattie (University of Western Sydney), Patricia Barkley (Citrus Australia Limited) and Ceri Pearce (Biosecurity Queensland, Department of Agriculture and Fisheries).

Last updated 12 September 2017