Xylella and exotic vectors


​​​​​ A leaf showing symptoms of xylella. Dehydration causes a scorching of the leaf surface.


Xylella and exotic vectors

Exotic to Australia

Life form: Bacterium
Origin: Americas
Distribution: Americas and the Caribbean, India, Iran, Europe,
Lebanon, Taiwan, Turkey and Israel
Features: Scorched leaves, browning and loss of leaves,
stunted shoots, reduced fruit size over time, dieback, death of plant
Pathways: Imported plant propagative material, insect vectors
At risk: Over 350 native, commercial and ornamental plant species


Hear about Australia’s most threatening plant pest from the Chief Plant Protection Officer in this​ short video

Xylella is an invasive bacterial plant pathogen that causes significant environmental and economic impacts. Many commercial and ornamental plant species can be killed by this bacterial pathogen.

Xylella is spreading around the world, and although it is not present in Australia, it is of major concern to Australia’s plant industries.

Depending on the host plant species, the disease is known by a range of common names, including:

  • Anaheim disease (in grapevine)
  • California vine disease (in grapevine)
  • dwarf (in lucerne)
  • leaf scald (in plum)
  • leaf scorch (in coffee, almond, blueberry, oleander, elm, oak, plane, mulberry, maple)
  • phony disease (in peach)
  • Pierce's disease (in grapevine)
  • variegated chlorosis (in citrus).

How to identify Xylella

Everyone needs to keep an eye out for symptoms of xylella and its insect vectors.


  • Spreads by people moving infected plant propagative material, and transmission by insect vectors which spread the pathogen to other plants. It is not carried on, or spread by seeds.
  • Grows within the xylem and clogs the water flow vessels of the plant causing the plant to dehydrate and eventually die.

Symptoms vary between hosts and can be easily confused with water stress or the presence of other pathogens.

Main symptoms are:

  • scorching of leaves
  • browning and loss of leaves
  • stunting of young shoots
  • gradual reduction in fruit size over time
  • dieback and eventual death of the plant.
Xylella in xylem vessel of citrus - K. Matsuoka, PaDIL
Xylella in xylem vessel of citrus
Leaf symptoms of Citrus variegated chlorosis - Alex. H. Purcell, University of California, Bugwood.org
Leaf symptoms of Citrus variegated chlorosis
Almond leaf scorch symptoms showing zonate pattern - Jack Kelly Clark, UC Statewide
Almond leaf scorch symptoms showing zonate pattern
Grapevine leaves showing scorch-like symptoms from Pierce’s disease - California Department of Food and Agriculture
Grapevine leaves showing scorch-like symptoms from Pierce’s disease
Olive tree displaying full decline - Luigi Paglia, Department of Agriculture, Water and the Environment
Olive tree displaying full decline


Some plants can be infected with xylella but not show any symptoms or significant effects.
Virtually all sucking insects that feed on a host plant’s xylem fluid are potential vectors of xylella, such as:

  • sharpshooters
  • spittlebugs
  • related leafhoppers.

Significant vectors such as meadow spittlebug (Philaenus spumarius) and the glassy-winged sharpshooter (Homalodisca vitripennis), which are not in Australia, have aided the establishment and significantly increased the impact of xylella in other countries. Spittlebugs are usually less than 13 mm long but may be up to 27 mm; while sharpshooters and froghoppers range in size from 2-30 mm but average 13 mm.

Meadow froghopper, Philaneus spumarius Source: CABI
small sucking insect known as meadow sharpshooter feeding on host plant stems. The insect’s wings are held like a tent over the body that is variably partnered with brown, black and white.
Glassy winged sharpshooter, Homalodisca vitripennis Source: C. Ray, invasive.org
Large sucking insect known as glassy-winged sharpshooter feeding on host plant stems. The insect inserts its needle like mouth parts into the plants xylem to feed from.


Many sucking insects already present in Australia are expected to be vectors and be able to spread the pathogen should it be introduced to Australia.


If you work around imported plant material, including cut flowers, nursery stock, fruit and vegetables, you need to look for disease symptoms and insect vectors.

Growers and home gardeners

You should only get plant material from clean, accredited suppliers. Check your plants frequently for any new pests or unusual symptoms, and always use good hygiene and biosecurity practices to prevent the entry, establishment and spread of pests and diseases.

Find out more about farm biosecurity.

Keep Xylella out of Australia

All Australians and international tourists have a role to keep out exotic pests and diseases. Xylella is present in a number of countries. Australia remains free of this exotic pest. We need your help to keep it this way.

Check what you can and cannot bring into Australia, whether you are a:

Xylella is Australia’s number 1 most unwanted

There is no evidence of xylella being successfully eradicated once it has established. For this reason, preventing the entry of this pathogen into Australia is vital.

Import restrictions and biosecurity measures

Some items, by law, are subject to certain import conditions to be allowed into Australia. Please check the Biosecurity Import Condition System (BICON).

Be aware of any xylella biosecurity measures that may be in place for incoming goods and conveyances. Industry advice notices are reviewed regularly and could change.

Secure any suspect specimens

Containment is critical. This could be as easy as bagging a suspect plant specimen that has symptoms or stopping an insect escaping by closing the doors on a shipping container.

Controlling vectors and removing infected plant material are the only control options, in conjunction with movement restrictions on infected plant material, to limit its spread. Identification and use of resistant plant stock may provide a long term management option, as the disease would be nearly impossible to eradicate.

Report detections of exotic pests

Any detections of xylella must be reported to the authorities.

Import community

If you receive or work around goods imported from overseas, including mail, you need to be vigilant to xylella and its insect vectors and other exotic pests. If you see an unusual pest, secure the goods to limit the movement of the pest and immediately report it to the Department of Agriculture, Water and the Environment See.Secure.Report. Hotline 1800 798 636 or by using the online form.

Growers and home gardeners

If you see symptoms of xylella, its exotic insect vectors or anything unusual, report it to the Exotic Plant Pest Hotline 1800 084 881. This will put you in touch with the department of primary industries or agriculture in your state or territory.

When reporting your concern, you will be given advice on handling the specimen and what to do next until an officer can investigate.

Additional information

Last reviewed: 4 February 2020
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