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Species Page

citrus canker

Xanthomonas citri
This information is part of a full datasheet available in the Crop Protection Compendium (CPC). Find out more information on how to access the CPC.
©CAB International. Published under a CC-BY-NC-SA 4.0 licence.

Distribution

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Extent
Invasive
Origin
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Host plants / species affected

Main hosts

show all species affected
Aegle marmelos (golden apple)
Casimiroa edulis (white sapote)
Citrus
Citrus aurantiifolia (lime)
Citrus aurantium (sour orange)
Citrus hystrix (mauritius bitter orange)
Citrus junos (yuzu)
Citrus latifolia (tahiti lime)
Citrus limetta (sweet lemon tree)
Citrus limon (lemon)
Citrus madurensis (calamondin)
Citrus maxima (pummelo)
Citrus medica (citron)
Citrus natsudaidai (natsudaidai)
Citrus reshni (Cleopatra mandarin)
Citrus reticulata (mandarin)
Citrus reticulata x Poncirus trifoliata (citrumelo)
Citrus sinensis (navel orange)
Citrus sunki (sour mandarin)
Citrus tankan (tankan mandarin)
Citrus unshiu (satsuma)
Citrus x paradisi (grapefruit)
Eremocitrus glauca (Australian desert lime)
Limonia acidissima (elephant apple)
Mangifera indica (mango)
Poncirus trifoliata (Trifoliate orange)

List of symptoms / signs

Fruit - lesions: black or brown
Fruit - lesions: scab or pitting
Fruit - premature drop
Leaves - abnormal colours
Leaves - abnormal forms
Leaves - abnormal leaf fall
Leaves - necrotic areas
Stems - canker on woody stem
Stems - dieback
Stems - discoloration of bark
Stems - internal red necrosis

Symptoms

Canker lesions begin as light yellow, raised, spongy eruptions on the surface of leaves, twigs and fruits. The lesions continuously enlarge from pin-point size over several months and can be of many different sizes based on the age of the lesion. As the lesions enlarge, the spongy eruptions begin to collapse, and brown depressions appear in their central portion, forming a crater-like appearance. The edges of the lesions remain raised above the surface of host tissue and the area around the raised portion of the lesion may have a greasy appearance. The lesions become surrounded by characteristic yellow halos. Canker lesions retain the erupted and spongy appearance under dry conditions, such as in a greenhouse; whereas they quickly enlarge and turn to flat lesions with a water-soaked appearance with frequent rain. Canker lesions vary in maximum size from 5 to 10 mm, depending on the susceptibility of the host plant. The symptoms are similar on leaves, fruit and stems.

Canker lesions are histologically characterized by the development of a large number of hypertrophic cells and a small number of hyperplastic cells. At an early stage of infection, the cells increase in size and the nuclei and nucleoids stain more easily; there is also an increase in the amount of cytoplasm synchronized with rapid enlargement. However, these hypertrophied cells do not divide; cell division is only detected in the peripheral areas of lesions adjacent to healthy tissue.

The lesions of canker B, C and D are similar in appearance and histology to those of canker A (Goto, 1992).

Reddy and Naidu (1986) reported canker lesions on roots; however, this has not been confirmed.

Prevention and control

Regulatory Control

Safeguards for exporting citrus fruits into the USA from Japan include: the establishment of isolated canker-free export areas; inspection of fruit by plant pathologists in both countries during harvesting and packing operations; pre-shipping surface sterilization with bactericidal dip; pre-shipping inspection using the bacteriophage method to ensure fruits are free of X. citri; and certification by the Japanese Plant Protection Service that fruits are free of X. citri (Goto, 1992).

Cultural Control

The disease has attracted widespread attention because of the serious efforts that have been made for eradication; these include destriction of citrus trees on a large scale and the implementation of strict international plant quarantine regulations against the pathogen (Stall and Civerolo, 1991; Goto, 1992).

The use of canker-free nursery plants is the first essential step in the management of citrus canker. Windbreaks established around citrus groves reduce disease. Pruning of angular shoots which hold canker lesions removes overseasoning inocula.  Periodic spraying with insecticides to control the leaf miner, Phyllocnistis citrella, reduces infection sites (Goto, 1992).

Biological Control

Interactions between X. citri and antagonistic bacteria including Bacillus subtilis (Pabitra et al., 1996), Pantoea agglomerans (Goto et al., 1979), Pseudomonas syringae (Ohta, 1983) and P. fluorescens (Unnamalai and Gnanamanickam, 1984) have been reported in vitro and in vivo. However, the practical usefulness of these bacteria in controlling the pathogen has not been proved.

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:

Impact

Losses due to citrus canker primarily result from defoliation, premature fruit abscission and blemished fruit. It is not uncommon for almost 100% of the fruits and leaves of young, susceptible trees to be infected. Development and the achievement of full growth may be delayed in severely infected, young trees.

The impact of the disease has not been fully elucidated by the assessment of loss. The practical risk of transcontinental dissemination of citrus canker through lesions on marketable fruits requires investigation.