Our site is currently being updated and pages are changing regularly. We thank you for your patience during this transition and hope that you find our new site easy to use.

Citrus canker

Have you seen citrus with these symptoms?

Citrus canker detected in the Northern Territory. A movement control order (PDF, 1.1MB) is now in place for citrus canker and carriers which means that host plants, planting materials and equipment may not be brought into Queensland. An industry alert has also been issued. This is to prevent it spreading into Queensland’s produce areas.

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

Be on the lookout for these symptoms and report them to Biosecurity Queensland on 13 25 23 or the Exotic Pest Plant Hotline on 1800 084 881.

Do not touch the lesions or move plant material off your property - this can spread the disease.

Early detection and reporting of symptoms are the key to controlling this disease.

General information

Citrus canker is a serious disease affecting citrus (and some other plant species of the Rutaceae family) caused by the bacterium Xanthomonas citri subsp. citri,

Citrus trees infected with citrus canker display unsightly lesions which can form on leaves, fruit and stems. Trees infected with the disease may suffer from low vigour and a reduction in fruit quality and quantity. Citrus canker impacts on citrus production and is the subject of a number of control and eradication programs around the world.

Citrus canker was detected in the Northern Territory in April 2018 and an emergency response to the disease is currently underway.

Overview

Cause Citrus canker is caused by the bacterium Xanthomonas citri subsp. citri.
Other names Citrus bacterial canker, Asiatic citrus canker.
Description

Citrus canker is caused by the bacterium Xanthomonas citri subsp. citri.

Citrus canker appears as raised spongy lesions on fruit, leaves, twigs and branches of affected trees. The lesions gradually increase in size to 5-10mm over several months. Eventually the lesions collapse, forming a crater-like appearance. The lesions become surrounded by a characteristic yellow halo, and the raised edges of the lesion may appear “slimy” or “greasy”.

The disease can cause characteristic lesions, abnormal leaf fall, dieback, blemished fruit, poor growth and premature fruit drop.

Distribution The disease is widespread in many tropical and subtropical citrus-growing areas of the world. Australia is considered free of citrus canker, other than the recent outbreak in the Northern Territory which is the subject of emergency response action.
Lifecycle

Bacteria exude from the lesions are spread by rain splash. In rain storms, bacteria can be carried between trees, up to 100 m. The disease can become latent in fields for long periods, and then become active again in periods of high rainfall and warm weather. The disease is not transmitted by seeds.

Disease spread can also be human assisted (for example on tools, machinery and equipment, by the movement of infected plant material, or on hands and clothes).

Crops affected Many citrus crops can be affected by citrus canker. These include orange, mandarin, lime, lemon, citron and grapefruit.
Hosts

All citrus cultivars can be affected (e.g. orange, mandarin, lemon, lime, grapefruit,  kumquat, tangelo, pomelo and citrus rootstock). However, some cultivars of citrus more readily develop canker lesions than others.

Citrus canker can also affect some native Australian Rutaceae species such as Citrus glauca (desert lime).

Symptoms

Blister-like formations (lesions) develop.

The lesions are usually:

  • raised
  • tan to brown in colour
  • surrounded by an oily, water-soaked margin and a yellow ring or halo.

Large or older lesions may have a crater-like appearance.

Leaf, fruit and stem tissue may be infected. Leaf tissue offers more opportunity for infection and as such typically displays the most numerous lesions over time. It is unusual to see multiple lesions on fruit or stems if lesions are not present on leaves.

Impacts

Citrus canker can cause plant defoliation, fruit blemish and premature fruit drop. This leads to a loss of saleable fruit.

Several countries consider citrus canker to be a quarantine disease, and its presence in Australia may affect export markets.

Spread

The canker lesions ooze bacteria when wet. Over short distances this bacterial ooze can be spread by rain splash or overhead irrigation systems. Citrus canker can be spread over longer distances on equipment (vehicles, tools, mechanical hedgers, sprayers, gardening equipment) and people (hands, shoes and clothing).

Movement of infected plant material, or airborne movement of bacteria as an aerosol or debris during severe weather events (where strong winds and rain are present), can also spread the disease further. Illegal importation of infected plant material poses the greatest risk of introducing this disease into Australia. The Department of Agriculture and Water Resources closely monitors for illegal plant movements and regulates approved host plant imports.

Risk period

Infections typically become active in early spring. The highest risk for new infections is during active growing periods where fresh shoots are emerging. Conditions for development of the disease are optimal in warm temperatures, and spread is highest in periods of high rainfall and strong winds.

Monitoring and action

Citrus canker is typically recognised by its characteristic symptoms, and can be detected during routine orchard inspections.

If you see symptoms, contact Biosecurity Queensland on 13 25 23, and they will advise how to take action.

Control

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

  • To avoid introducing citrus canker on to your property, establish new plantings with healthy plant material from reputable nurseries that use Auscitrus seed and budwood, which is routinely tested for a range of diseases. On receipt of any new plants, check that they are pest and disease free. If citrus canker is detected, isolate suspect nursery stock from healthy plants until official checks are completed.
  • Keep your farm clean. Use good sanitation and hygiene practices. Remember that workers, visitors, vehicles and equipment can spread diseases. Make sure equipment is clean before it enters your farm.
  • If you have been to an overseas country that has citrus canker, do not wear your travel clothes into your orchard until after they have been washed in hot soapy water.
  • Make sure that you and your farm workers are familiar with the symptoms of citrus canker. Regularly check your orchard and report any unusual or unfamiliar symptoms.

.

Quarantine restrictions

Queensland has a movement control order in place for citrus canker. You may not move any host plant, planting media, soil, or machinery and equipment that has been used for production.

If the disease is suspected please call Biosecurity Queensland on 13 25 23.

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

More Information

Movement Control Order Notice Citrus canker and carriers (PDF, 1.1MB)

Citrus canker industry alert

Further information