Bacterial blight
Causal organism: Xanthomas axonopodis pv. punicae Symptoms
- Small, irregular, water soaked spots appear on the leaves.
- Spots vary from two to five mm in diameter with necrotic centre of pin-head size.
- Spots are translucent which turn light brown to dark brown after sometime and are surrounded by prominent water-soaked margins. Spots coalesce to form large patches.
- Severely infected leaves defoliated.
- The bacterium attacks stems, branches and fruits also.
- On stem, the disease starts as brown to black spots around the nodes .It further causes girdling and cracking of nodes. Finally the branches get broken.
- Brown to black spots formed on fruits which are raised and oily in appearance.
![Bacterial ooze from the fruit Bacterial ooze from the fruit](/moodle/file.php/96/Bacterial_blight_pomegranate.jpg) Etiology
- It is a Gram-negative rod, motile with single polar flagellum. It is non acid fast and aerobic.
- Mode of spread and survival
- The bacterium survives on the tree.
- The pathogen survives for 120 days on fallen leaves during the season.
- The primary infection occurs through infected cuttings.The disease spreads through wind and splashed rains.
Epidemiology
- High temperature and low humidity favour the disease. Temperature of 30 - 34° C and relative humidity (80 to 85%) is favourable for multiplication of the pathogen.
Management
- Clean cultivation and strict sanitation in the orchards help in reduction of disease incidence.
- Collect and burn the fallen leaves
- Spraying of 1 % urea solution on fallen leaves enhances their degradation process.
- Bleaching powder spray on the fallen leaves reduces the inoculum
- Spraying Bordeaux mixture (1.0%) controls the disease.
- Spray 0.05% streptocycline to control the disease
- Copper oxy chloride spray (0.3% concentration) can also be done.
- Pruning at correct stage would reduce the disease(Bahar pruning)
- Ganesh has been found to be a moderately resistant variety for bacterial blight disease
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Last modified: Tuesday, 24 January 2012, 4:18 AM