Bacterial blight: Necrotic spot on leaves
Pathogen: Xanthomonas axonopodis pv. punicae
Symptoms
Water soaked spots or necrotic spots with yellow halo or irregular brownish black spots on leaves:
Symptoms of bacterial blight appear first on leaves as small, irregularly shaped, water-soaked spots. They vary from 2 to 5 mm in diameter and have necrotic centers. The water-soaked spots, when viewed against light, look translucent. They turn light brown gradually and then dark brown and are surrounded by prominent water-soaked margins. Severely affected leaves become yellow and are easily shed. Bacterial ooze is sometimes found in the centers of the spots.
Disease development
Infected fruit and twigs are potential sources of primary inoculum. The secondary spread of bacterium is mainly through rain and spray splashes, irrigation water, pruning tools, humans, and insect vectors. Entry is through wounds and natural openings. The first water-soaked lesions develop within 2–3 days and appear as dark red spots. Disease buildup is rapid from July to September. Severity increases during June and July and reaches a maximum in September and October and then declines.
Control
Select disease free planting material. Spray Bordeaux mixture (1.0%). Spray with Streptocycline (0.025%) in combination with Copper oxychloride (0.25%) or Carbendazim (0.15%) at 15 days interval for 5-6 times starting from leaf initiation stage. If possible, cut ends should be pasted with Bordeaux (10%) paste.