Citrus canker

Have you seen citrus with these symptoms?  

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.  

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.  

Call us on 13 25 23  

General information

Citrus canker is a contagious disease of citrus (and some other plant species of the Rutaceae family) caused by the bacteria Xanthomonas citri. Infected trees 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 is a serious disease impacting on citrus production and is the subject of a number of control and eradication programs around the world.

Overview

Cause Citrus canker is caused by a bacterial infection which causes spongy, eruptive lesions on fruit, leaves, and branches of citrus.
Other namesCitrus bacterial canker
Description

Citrus canker is caused by bacteria, Xanthomonas citri.

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

The disease can cause characteristic lesions, abnormal leaf fall, die back, discolouration, poor growth and economic loss.

DistributionThe disease is widespread in many tropical and subtropical citrus-growing areas of the world. Australia is currently free of citrus canker. Outbreaks in Australia are rare, with the last detection in Emerald, Queensland, in May 2005. This area was declared free of citrus canker in 2009.
Lifecycle

Inoculum remains in the lesions of plants from year to year (overwintering), and are the primary source of new infections. Bacteria can also survive on straw or mulch, or in soil. Active infections typically begin in early spring.

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

Crops affectedMany citrus crops can be affected by citrus canker. These include limes, lemon, citron, mandarin, orange, and grapefruit. Citrus canker can also infect cumquat and mango.
Hosts

All citrus cultivars can be affected (e.g. orange, lemon, lime, grapefruit, mandarin, 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),  Acronychia acidula (lemon aspen),  Micromelum minutum (lime berry) and  Murraya paniculata var.  ovatifoliolata (native mock orange). Other plants such as wampee ( Clausena lansium), white sapote ( Casimiroa edulis) and elephant apple ( Feronia limonia) are also known hosts

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 fall. 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.

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Quarantine restrictions

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.

Further information

Last updated 25 August 2017