The bacterium Xanthomonas citri subspecies citri (also known as X. axonopodis pv. citri) is the cause of citrus canker. There are pustules on the fruit, stems, and leaves due to infection.

1. Citrus Canker
Presented By :
Prof. Shubhangi Patil,
Department of Botany,
Miraj Mahavidyalaya,
Miraj
Plant Pathology For U.G. Students

2. Introduction
• It causes necrotic lesions on fruit, leaves and twigs.
• Losses are caused by reduced fruit quality and quantity and
premature fruit drop.
• The market value of the canker affected fruits is very much
reduced.
• The most serious bacterial disease, affecting all types of
important citrus crops.

3. Host Plant: Citrus species Viz. C. medica ( Lemon),
C. reticulata (Orange), C. limetta ( Sweet Lemon / Mosambi)
Family: Rutaceae
Causal Organism : Xanthomonas axonopodis pv. Citri
Xanthomonas axonopodis is a rod-shaped Gram-negative
bacterium with polar flagella. A number of types of citrus
canker diseases are caused by different variants of the
bacterium

4. • It is a gram negative, monotrichous, capsulated bacillus
which is strictly aerobic in nature.
• It is 1.5-3 micrometer in length and 0.5-1.5 micrometer in
breadth.
• The bacteria does not produce endospores and cannot
reduce nitrates.
(a) Bacterial Canker of Citrus, (b) Bacterial colonies c) Gram negative bacteria

5. Symptoms
•Necrotic lesions produced on young leaves, twigs and
fruits.
•Attack on leaves, twig, petiole, branches, fruit, thrones.
•Small, round, watery, translucent raised, yellow brown
spots on leaves and old branches.
•Spots- white to greenish & finally rupture–rough corky.
•Rough lesions surrounded by-yellow brown to green
raised margin & watery yellow halo.
•Crater like appearance is common in leaves.
•Fruitlesion become rough & corky.
• Defoliation

6. Symptoms
Raised canker lesions
on lower leaf surface
Corky lesions with
crater in center
Water-soaked
margin around
necrotic area
Yellow halos around
leaf lesions
Canker lesions on
fruit
Canker lesions on
stem

7. • Bacteria develops symptoms on leaves, stem and fruits.
• During warm, rainy weather they ooze out of lesions and, if splashed
onto young tissues, bacteria enter them through stomata or wounds.
• Bacteria infect older tissues only through wounds.
• Several cycles of infection can occur on fruit; therefore, fruits often
have lesions of many sizes.
• Free moisture and strong winds seem to greatly favor the spread of
the bacteria.
• The disease seems to be much more severe in areas in which the period
of high rainfall coincide with the period of high mean temperature,
whereas it is not important in areas where high temperatures are
accompanied by low rainfall.
Disease Cycle

8. Disease Cycle
Fig: Disease cycle of citrus canker caused by Xanthomonas axonopodis pv. Citri

9. Control Measures
• Strict quarantine measures should be practiced to
exclude the pathogen in canker-free citrus producing
areas.
• Selection of healthy nursery plants.
• Eradication of bacterium by burning all infected and
adjacent trees to prevent the spread of the pathogen.
• Prune the affected parts and spray with bactericide
(copper oxy-chloride).
• Wind break should be used to stop the movement of
pathogen due to wind.

10. References
• (2017, 5 17). Retrieved from
https://en.wikipedia.org/wiki/Citrus_canker.
• Agrios, G. N. (2006). Plant Pathology (Fifth ed.).
Elsevier Academic Press.
• Gottwald, T. R., Graham, J. H., & Schubert, T. S. (2002.,
August 12). Citrus Canker: The Pathogen and Its Impact.