Citrus Canker

Xanthomonas axonopodis

Citrus Canker

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A close up of a fruit
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Xanthomonas is a genus of bacterial plant pathogens. Species in the group demonstrate high specificity to different plant species. Many important Xanthomonas pathogens are split into groups called pathovars (abbreviation pv.). A pathovar is a bacterial strain or group of strains which share similar characteristics, (i.e. produce similar symptoms) but use different plants as hosts. Citrus Canker is caused by the pathovora Xanthomonas axonopodis pv. citri. As suggested by its name, it attacks Citrus plants, and can significantly impact the health of the plants it infects. Some of the crops commonly affected include lime, oranges, and grapefruit, which develop dark lesions on the fruits, stems and leaves.

Growth factors

Spreads during humid, wet weather. Thrives in warm subtropical regions.


Open lesions in trees, otherwise known as canker.
Black spots on leaves, fruits and stems.
Shoot dieback
Premature fruit fall

Biological treatment

If you suspect a plant is infected, remove and destroy plants (or diseased-parts) promptly. Ensure all plant matter is cleared and removed. There is currently no treatment to cure Citrus Canker. Management and prevention is the only way to control Citrus Canker.


The disease-causing bacteria lay dormant within lesions on the plant. When conditions become optimum, and there is sufficient moisture, the bacteria ooze from the plant. During wet weather bacteria is transmitted through water droplets and carried by the wind, which is how the disease infects new hosts. The bacteria enter plants through natural openings, such as the pores or open wounds.


Use filters when collecting rainwater to avoid infected plant matter contaminating supply. Avoid overwatering plants. Water should be able to evaporate quickly so that bacteria doesn't have a medium to travel through. Maintain good tool hygiene. Be sure to clean tools, boots and vehicles if you treat a plant which shows symptoms.

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