Citrus canker

Scientific name

[Bacterium] Xanthomonas axonopodis pv. citri (Hasse) Vauterin et al. Synonyms: Xanthomonas campestris pv. citri

Different strains of citrus canker have been reported throughout the world. The Asiatic strain (A-strain) is the most widespread and severe form. Strains can be differentiated by molecular tests and hosthost:
an organism that is infected with or fed upon by a pathogenic or parasitic organism
range.

Other common names

Asiatic citrus canker

Disease cycle

Citrus canker is not vectored by any organism but is spread by wind-driven rain. However, wounds caused by feeding of the Asian citrus leaf miner (Phyllocnistis citrella Stainton) may serve as an entry point for the bacterium if citrus canker inoculuminoculum:
a.) the pathogen or its part that causes infection of the host b.) small amount of a microorganism that is transferred to a substrate or a culture medium in order to propagate it
is present.

Symptoms

Leaf - typical citrus canker lesions on leaves will range from 2-10 mm in size and will have raised concentric circles on the underside of the leaf. Frequently lesions will be surrounded by a water-soaked margin and a yellow halo. As a canker lesionlesion:
any defined area of living tissue that has been structurally modified as a result of a disease or damaging process
ages, it may lose it palpable roughness, but the concentric circles will still be visible with a hand lens (on the underside of the leaf). The yellow halo eventually changes to dark brown or black and the water-soaked margin surrounding the lesionlesion:
any defined area of living tissue that has been structurally modified as a result of a disease or damaging process
may diminish. The middle of the lesionlesion:
any defined area of living tissue that has been structurally modified as a result of a disease or damaging process
(on underside of leaf) will be corky in texture with a volcano or pimple-like point. With the exception of very young lesions, lesions always penetrate through both sides of the leaf. In the presence of damage, the lesionlesion:
any defined area of living tissue that has been structurally modified as a result of a disease or damaging process
may follow the contours of the damage and therefore may not be circular. In older lesions, a saprophytic white fungus may grow over the center of the lesionlesion:
any defined area of living tissue that has been structurally modified as a result of a disease or damaging process
. The center of a lesionlesion:
any defined area of living tissue that has been structurally modified as a result of a disease or damaging process
may fall out producing a shot hole appearance.

Fruit - typical citrus canker lesions on fruit will range from 1-10 mm in size. Larger lesions usually penetrate a few millimeters into the rind. Fruit lesions may vary in size and may coalesce. Fruit lesions consist of concentric circles. On some varieties these circles are raised with a rough texture on other varieties the concentric circles are relatively flat like the surface of a record. The middle of the lesionlesion:
any defined area of living tissue that has been structurally modified as a result of a disease or damaging process
will be corky in texture with a volcano or pimple like point. The center of a lesionlesion:
any defined area of living tissue that has been structurally modified as a result of a disease or damaging process
may crack and has a crusty material inside that resembles brown sugar. Frequently on green fruit a yellow halo will be visible; however it will not be visible on ripened fruit. Lesions may have a water-soaked margin and the water-soaked margin is especially evident on smaller lesions. In the presence of damage the lesionlesion:
any defined area of living tissue that has been structurally modified as a result of a disease or damaging process
may follow the contours of the damage therefore not being circular. In older lesions a saprophytic white fungus may grow over the center of the lesionlesion:
any defined area of living tissue that has been structurally modified as a result of a disease or damaging process
.

Regulatory information

The most current regulatory information can be found at:

http://www.aphis.usda.gov/plant_health/plant_pest_info/citruscanker/index.shtml

Host range

Citrus canker affects multiple genera in the family Rutaceae. Citrus canker is most severe on grapefruit, key/Mexican lime, lemons, and kaffir lime.

Distribution

Citrus canker is thought to have originated in southeast Asia. Different strains of citrus canker are widespread throughout many tropical and subtropical areas of the world. In the United States and its territories citrus canker is only found in Florida as of 2009.

Easily confused with

On leaves, citrus canker may be confused with citrus bacterial spot (CBS), greasy spot, citrus scabscab:
rough, crust-like, diseased or injured area on the surface of a plant
, and leprosis. On fruit, citrus canker may be confused with alternaria, citrus scabscab:
rough, crust-like, diseased or injured area on the surface of a plant
, damage, and leprosis.