Citrus canker (Xanthomonas citri subsp. citri)

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PLANT PEST

Citrus canker

Exotic to Australia

Life form: Bacterium
Origin: South East Asia
Distribution:Africa, Asia, Middle East, North & South America,
some Pacific Islands
Features: Forms lesions on fruit, leaves and branches, causing dieback
Pathways: Movement of infected plant material, rainstorms, wind blown
At risk: Commercial citrus varieties & relatives


Citrus canker is a serious bacterial disease of commercial varieties of citrus, and relatives, caused by the bacterium Xanthomonas citri subsp. citri. The disease affects the leaves, twigs and fruit causing the leaves to drop and fruit to fall to the ground before it ripens.

Citrus canker has resulted in heavy economic losses to citrus industries across the globe, due to damage to trees, reduced fruit production and access to export markets and increased cost of management.

Outbreaks of this disease have previously been eradicated from Queensland and the Northern Territory at great cost to industry and growers. The last detection was in Emerald in May 2005 and Australia was declared free of citrus canker in 2009.

The islands of Torres Strait provide a potential pathway for serious pests such as citrus canker to get into Australia from countries to our north.

See if you can identify the pest

Everyone needs to keep an eye out for symptoms of citrus canker.

Xanthomonas citri subsp. citri causes warty, rust-brown spots (cankers) that form on the leaves, twigs and shoots. The cankers on leaves are rough to touch on both upper and lower surfaces and are surrounded by a distinctive bright yellow halo. Scabby cankers also appear on the fruit.

Citrus canker is most severe in hot, wet areas. Strong winds and rain help it to spread from tree to tree. The canker lesions ooze bacterium when wet and these can be spread by rain splash or overhead irrigation systems over short distances. Citrus canker can spread quickly over long distances on infected citrus fruits and leaves, people and equipment.

Report crusty, tan spots on citrus leaves, fruit or twigs. Look for leaf spots with a yellow halo.

Importers

Illegal importation of infected plant material poses the greatest risk for the disease to enter Australia. If you work around imported plant material, including citrus fruit and plants, you need to look forbrown lesions on leaves, stems and fruit.

Growers and home gardeners

Ensure that propagation material is purchased from suppliers that source their budwood from Auscitrus.
If citrus canker became established in Australia it would affect:

  • All citrus cultivars (orange, lemon, lime, grapefruit, mandarin, kumquat, tangelo, pomelo and citrus rootstock)
  • elephant apple (Feronia limonia)
  • native Australian Rutaceae species, such as desert lime (Citrus glauca), lemon aspen (Acronychia acidula), lime berry (Micromelum minutum) and native mock orange(Murraya paniculata var. ovatifoliolata).
  • wampee (Clausena lansium)
  • white sapote (Casimiroa edulis).

Protect your farm from biosecurity risks, practice good on-farm biosecurity and regularly monitor your orchard.

Warty, rust brown spots on leaves (Source: DAWR)

Multiple leaves from a citrus plant displaying citrus canker. Leaves are covered in random parts with warty rust brown spots. The level of infestation varies on each leaf.
Citrus canker infected fruit, stems and leaves (Source: Timothy Schubert, bugwood.org)
Five pieces of citrus fruit infected with citrus canker. The fruit displays the same warty brown spots on the fruit regardless of how ripe the fruit is.

Check what can legally come into Australia

All Australians and international tourists have a role to keep out exotic pests and diseases.

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:

Don’t let your citrus get sick

The only way to rid citrus orchards of the disease is to replace infected trees, so the cost of an outbreak to Australia’s citrus industry would be enormous. If citrus canker established in Australia, citrus trees could become weak, unproductive and unprofitable.

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 citrus canker 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.

Look out for scabby marks on leaves and fruit. If you think you see evidence of citrus canker take a photo and record the location.

Report detections of exotic pests

Any detections of citrus canker 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 citrus canker 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 and Water Resources SEE. SECURE. REPORT. Hotline 1800 798 636 or by using the online form.

Growers and home gardeners

If you see infected plant tissue with citrus canker 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

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