Citrus Canker:
essential data |
Disease Name, Other
Names, Crops Affected Causative
Agent, Synonyms,
Description
of the Agent Symptoms Prevention
and Treatment
Other Comments |
| Disease name |
Citrus Canker |
| Other Names |
- Asiatic citrus canker or cancrosis A,
- False citrus canker or cancrosis B
- Mexican lime cancrosis or cancrosis C.
|
Causative Agent
|
Xanthomonas axonopodispv.citri |
| Synonyms |
- Bacillus campestris
- Bacterium campestres
- Phytomonas campestris
- Pseudomonas campestris
- Xanthomonas campestris pv. citri
- Xanthomonas citri
The "pv." stands for "pathovar," a disease causing variant of a bacterium
that affects a specific group of plants. In this case, pv. citri
attacks citrus plants. |
| Crops Affected |
Citrus crops and many other related plants belonging
to the family Rutaceae. Particulary badly affected are:
- grapefruit;
- lemon;
- lime;
- trifoliate orange.
Other citrus crops are also affected, but less severely. |
| Description of the Agent |
X. campestris is a bacterium belonging to the biochemically
versatile gamma Proteobacteria. It is Gram negative (stains red in
the Gram stain), aerobic and does not form spores. It overwinters
in diseased trees and is spread when it oozes from scabs during wet
weather. Wind driven rain is its primary mode of transmission. The
bacterium is well suited to spread in the warm wet areas where citrus
grows freely.
The pathogen enters the plant through wounds and another natural
opening: the stomata through which leaves take oxygen in. It has
no mechanisms of its own to invade a healthy plant.
|
| Symptoms |
The disease can appear anywhere on the exposed surface of the plant.
Lesions first appear as moist spots that enlarge and grow into raised
white scabs that are a result of the bacterium stimulating cells to
divide. The scabs darken and become cratered and surrounded by yellowed
tissue or they may merge into large scabs. Lesions on fruit do not
actually enter the flesh of the fruit, but the cratered appearance
makes the fruits unmarketable. |
| Prevention and Treatment |
Resistant varieties of many citrus crops are available
and canker on them can be controlled by early spraying with copper
compounds. Windbreaks are also used to prevent wind-driven spread.
Immediate and rapid destruction of infected trees and strict quarantine
are essential to controlling the spread. |
| Other Comments |
Citrus canker is the most feared disease of citrus crops
and when established it can take years to eradicate and the destruction
of millions of trees and many livelihoods. It is endemic in Japan
and Southeast Asia. |