Citrus canker

Xanthomonas axonopodis pv. citri, Syn. X. citri, Pseudomonas citri

Citrus canker

Citrus canker

Legal Status: Notifiable Organism
Status in New Zealand: Not in New Zealand
Organism: Micro-organism

Image at right: Lesions on fruit of citrus tangelo variety.
Images courtesy of Liberato JR, Miles AK, Rodrigues Neto J & Gambley C (2006)
Citrus canker (canker A) (Xanthomonas axonopodis pv. citri) - http://www.padil.gov.au (offsite link to www.padil.gov.au)

This disease is NOT in New Zealand.

Report sightings to MPI’s exotic pest and disease hotline ph 0800 80 99 66.

General Information

Citrus canker is a leaf and rind spotting disease of commercial citrus cultivars and some citrus relatives. The most serious and widespread strain of this disease (Asian or A-strain) is caused by the bacterium Xanthomonas axonopodis pv. citri.

Citrus canker is not in New Zealand and is thought to have originated in south-eastern Asia or India. It has spread through much of Asia, to Japan, southern and central Africa, the Middle East, Australia, Pacific Islands, South America and the south-eastern United States.

Severe infections of citrus canker may cause defoliation, dieback, severely blemished fruit, reduced fruit quality and premature fruit drop. Symptoms of citrus canker can appear on all parts of the plant above the ground, including leaves, twigs and fruit and particularly young, actively growing parts.

On stems and fruit, canker lesions are raised and corky and surrounded by an oily or water-soaked margin. No yellowing (chlorosis) surrounds twig lesions, but it may be present around fruit lesions. Lesions may be irregularly shaped and sunken. Sunken craters can occur on fruit but the lesions do not penetrate deep into the rind.

There is no cure for citrus canker. The only effective means of control is to remove and burn infected trees.

brown spots on leaf raised brown lesions on shoot of citrange Troyer

Lesions on lower leaf surface (left) and shoot (right) of citrange Troyer.

Frequently Asked Questions

How could this disease reach New Zealand?

This disease has the potential to be introduced into New Zealand’s citrus orchards through the inadvertent importation of infected citrus fruits and seedlings.

What damage could it cause?

Although, this disease is not harmful to humans, an infected fruit would be too unsightly to be sold. Citrus canker can also significantly affect the vitality of citrus trees. It causes leaves and fruit to drop prematurely, until ultimately the trees produce no fruit at all and die.

If this disease was to get to New Zealand, there would major economic impact on the country's citrus industry. Not only through the reduction of export and domestic fruit sales, but also from the destruction of productive trees in attempts to eradicate the disease.

How could it spread?

Internationally, this disease spreads via infected nursery stock and diseased fruit. Short distance spread also occurs via wind-driven rain, overhead irrigation, and on the clothing and equipment of orchard workers.

Useful Resources

Page last updated: 11 June 2014