September Pest of the Month: African citrus psyllid

Name: African citrus psyllid, Trioza erytreae

The main economic importance of T. erytreae is that it is the vector of the very serious citrus huanglongbing disease caused by Liberibacter species. While the insect itself is a minor citrus pest, huanglongbing is a serious threat to citrus-producing areas worldwide.

The African citrus psyllid, Asiatic citrus psyllid and huanglongbing disease are not known to occur in Australia. If these pests become established in Australia, they have the potential to cause major crop losses and any farm/orchard infested can be quarantined. All citrus cultivars are a host for African citrus psyllids (e.g. orange, lemon, lime, grapefruit, mandarin, cumquat, tangelo, pomelo, native citrus and citrus rootstock). Native and exotic mock orange/orange jasmine (Murraya spp.), white ironwood (Vepris lanceolata), lime berry (Triphasia trifolia) and horsewood (Clausena anisata) are also hosts.T. erytreae affects other species in the Rutaceae family, and can feed on Cape chestnut (Calodendrum capense), orange-climber or forest-pepper (Toddalia asiatica) and small knobwood (Zanthoxylum capense).

Similar to:

Trioza erytreae is similar to Diaphorina citri, the Asian citrus psyllid, both of which are vectors of citrus huanglongbing (greening) in Asia and other parts of the world. The geographical range of the two species did not originally overlap, but they now occur together in some regions.

Description:

African citrus psyllid (Trioza erytreae del Guercio) is a sap-sucking insect. It prefers cooler, moist climates and is very sensitive to extremes of hot, dry weather. Long-distance spread most commonly occurs via movement of infested plant material. Short-distance dispersal can be wind-assisted for these short-distance fliers.

Eggs are tiny, yellow or orange, cylindrical, and have an upturned, sharp point. They are laid on leaf margins, along the midribs and occasionally on flower buds and young fruit. Nymphs are tiny (0.3-1.6mm long) with colour varying from yellow, olive-green to dark grey.

Nymphs are flat with a distinct marginal fringe of white, waxy filaments. On their fifth instar, two pale brown spots appear on the abdomen. They are mainly found on new flushing citrus growth. The nymphs 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.

Adults are small, about 4mm long, with a brown-grey abdomen and a black head. Males have an abdomen that ends in a blunt tip while the female’s abdomen ends in a sharp point. The forewings are large and transparent with clearly defined veins.

Damage:

When African citrus psyllid nymphs feed, they can cause distinctive cup-shaped or pit-like galls to form in leaves, particularly on the lower leaf surface of immature leaves. These are often visible as bumps on the upper leaf surface. They can cause severe leaf distortion, curling, stunting and leaf yellowing.

The psyllids excrete pellets of honeydew that look like tiny, white eggs. The ground surface or vegetation under a badly infested tree can look like it has been dusted with white powder.

For more information refer to the pest management plan on galling insects or  the industry Pest ID Tool www.pestid.com.au

Note that the Pest ID tool is now available with free access to industry

An initiative of the Nursery Levy funded National Nursery Industry Biosecurity Program (NY15004) and ‘Building the resilience and on-farm biosecurity capacity of the Australian production nursery industry’ Project (NY15002).