Citrus canker

Citrus canker is a widespread disease of Citrus plants all over the world. this ppt explains causative organism, symptoms and control measures of citrus canker.

1. CITRUS CANKER Dr. Sr. Meena K Cheruvathur Assistant Professor Department of Botany St. Mary’s College Thrissur

2. Citrus canker, Dr. Sr. Meena . K. Cheruvathur , St. Mary’s College, Thrissur CITRUS CANKER Citrus is a common term used for fruits of Genus C itrus belongs to family Rutaceae . It is a native of Australia and now cultivated in all over the world. Citrus canker is originated in China. It is a wide spread disease in all citrus growing areas of the world now. SYMPTOMS. The disease occurs on leaves, twigs, thorns, older branches and fruits . Lesions first appear on the lower side of the leaves as small, round, watery, translucent spots . They are raised and become yellowish brown.

3. Citrus canker , Dr. Sr. Meena . K. Cheruvathur , St. Mary’s College, Thrissur CITRUS CANKER SYMPTOMS

4. Citrus canker , Dr. Sr. Meena . K. Cheruvathur , St. Mary’s College, Thrissur The spots 1mm to 1 cm increase in size and coalesce to form elongated lesions on fruits and twigs. In advanced stages surface of the spots become white or grayish. Finally centre of the spots ruptures, giving a rough, corky crater like appearance. The rough lesions surrounded by yellowish brown to green raised margin and watery yellow halo. Spots occurring on midrib of leaves and petioles cause premature defoliation. Cankers on twigs cause them to break.

5. Citrus canker, Dr. Sr. Meena . K. Cheruvathur , St. Mary’s College, Thrissur

6. Citrus canker , Dr. Sr. Meena . K. Cheruvathur , St. Mary’s College, Thrissur As the lesions age, gradually increase in size to 5-10mm over several months. Large or older lesions may have a crater-like centre, which can fall out to create a ‘shot-hole’ appearance, occur in clusters where water pools on the leaf (such as along leaf margins or tips). It can follow the feeding tracks of citrus leaf miners, where the wound provides an entry point for the bacteria. Multiple lesions on fruit or stems are seen in cases where the foliage is severely affected.

7. Citrus canker, Dr. Sr. Meena . K. Cheruvathur , St. Mary’s College, Thrissur On larger branches cankers/lesions are large, irregular, rougher and more prominent. Cankers on fruits are similar to those on leaves, but yellow halo absent. In fruits, crater like depression in the centre is more prominent. Injury to fruits is only skin deep and no effect on pulp or juice.

8. Citrus canker, Dr. Sr. Meena . K. Cheruvathur , St. Mary’s College, Thrissur Pathogen Gram negative, aerobic bacterium Xanthomonas citri is the causative organism.

9. Citrus canker, Dr. Sr. Meena . K. Cheruvathur , St. Mary’s College, Thrissur Pathogen Wet weather ( rainy season) and mild temperature (between 20 - 30 degree) is favorable for disease development. Presence of free moisture on host surface for at least 20 minutes support successful infection . Bacterium enters the host through natural openings like stomata and through wounds . It multiply in the intercellular spaces, dissolves middle lamella and establishes in the cortical region.

10. Citrus canker, Dr. Sr. Meena . K. Cheruvathur , St. Mary’s College, Thrissur Spread of disease Bacteria does not survive in soil or infected plant parts fallen on the ground. Attacked twigs bearing old lesions on the tree are main source of perenation of the pathogen. Bacteria from the cankers are mainly disseminated by 1. Rain splashes 2. Insects (Citrus leaf miners) and 3. Transfer of disease through infected nursery stock

11. Citrus canker , Dr. Sr. Meena . K. Cheruvathur , St. Mary’s College, Thrissur Control measures Very difficult to control. Only practical method is destruction of the diseased plants by burning them. Use of disease free nursery stalk. Spraying of 1% bordeaux mixture before planting in new orchards. In old orchards, pruning of the affected twigs, Spraying of 1% bordeaux mixture at periodical intervals especially rainy season. Burning of dropped of leaves and twigs. The vigour of the plant should be maintained by proper irrigation and fertilization. Proper care given to minimize the attack of leaf miners . Rigidly follow quarantine measures. Development of resistant varieties

12. Citrus canker , Dr. Sr. Meena . K. Cheruvathur , St. Mary’s College, Thrissur References : https:// www.agric.wa.gov.au/citruscanker/citrus-canker-declared-pest?page=0%2C1 https://www.easybiologyclass.com/citrus-canker-symptoms-causal-organism-and-control-measures-pathology-lecture-notes / https://www.plantmanagementnetwork.org/pub/php/review/citruscanker/

13. Citrus canker, Dr. Sr. Meena . K. Cheruvathur , St. Mary’s College, Thrissur