- On leaves may be confused with citrus bacterial spot (CBS), greasy spot, citrus scab, and leprosis
- On fruit may be confused with alternaria, citrus scab, damage, and leprosis
- Spread by wind-driven rain
- Citrus canker is not vectored
- Asian citrus leaf miner wounds may serve as an entry point for the bacterium
- Found on fruit, leaves and stem
- http://idtools.org/id/citrus/diseases/factsheet.php?name=Citrus+canker
- Found on both sides of leaf
- Raised leisions
- Sometimes holes in leaves
- Juice from fruit is okay to drink
- Mongi Zekri Ph.d UF/IFAS 5-County Agent
- Most infections occur between April and July on oranges
Three to four applications of copper-containing materials at 3-week intervals should be sufficient to obtain relatively clean fruit. - Grapefruit are susceptible to canker for a much longer period.
Copper sprays should begin when the fruit is ¾ inch diameter and continue at 3 week intervals until fully grown in October for best results - Copper does not move from where it was applied, so as fruit grows, the new tissue does not have copper to protect it. Disease control on leaves is not possible because of their rapid growth.
- Homeowners should be aware that these disease management strategies are not completely reliable, but will minimize the disease on trees
- http://edis.ifas.ufl.edu/pp116
Citrus Canker Disease on 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 lesion will be corky in texture with a volcano or pimple like point. The center of a lesion 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 lesion 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 lesion.
http://edis.ifas.ufl.edu/pp116
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| crater-like lesions |
Citrus Canker Disease on Stem
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| outer layer of bark removed to show brown lesions |
Citrus Canker Disease on Leaves
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 lesion 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 lesion may diminish. The middle of the lesion (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 lesion 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 lesion. The center of a lesion may fall out producing a shot hole appearance.
http://edis.ifas.ufl.edu/pp116
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| Yellow halo surrounding leaf lesion |
Resources
http://idtools.org/id/citrus/diseases/factsheet.php?name=Citrus+canker
http://edis.ifas.ufl.edu/pp116
http://edis.ifas.ufl.edu/pp136
https://edis.ifas.ufl.edu/ch199
