Bacterial Leaf Streak :Causal organism: Xanthomonas oryzae pv. oryzicola

Symptoms :

• Fine translucent streaks are formed on the veins and the lesions enlarge lengthwise and infect larger veins and turn brown
• On the surface of the lesions, bacterial ooze comes out and form form small yellow band-like exudates under humid conditions.
• In severe cases the leaves dry up.

• The bacterium is aerobic, gram negative, non spore forming, rod with size ranging from 1-2 x 0.8-1.0􀀀m with monotrichous polar flagellum..
• Bacterial colonies are circular, convex with entire margins, whitish yellow to straw yellow colored and opaque.

Favourable conditions/Epidemiology:

• Clipping of tip of the seedling at the time of transplanting.
• Heavy rain, heavy dew, flooding, deep irrigation water.
• Severe wind and temperature of 25-30 °c
• Application of excessive nitrogen, especially late top dressing

Mode of spread and survival: :

• It is transmitted through seeds and infected stubbles to the next planting season.
• The pathogen spreads through irrigation water and also through rain storms.

Management:

Cultural method :

• Burn the stubbles.
• Use optimum dose of fertilizers.
• Avoid clipping of tip of seedling at the time of transplanting.
• Avoid flooded conditions.
• Remove weed hosts periodically.

Chemical Method :

• Seed treatment: Soaking of seeds in streptomycin sulphate 90% and tetracycline 10% SP @ 40 ppm for 12 hours or seedling root dipping @ 40 ppm for 30 minutes.
• Foliar spray in the main field @ 100-150 ppm. Repeat the spray after 15 days, if required.

Source of information:

• AICRIP rice, TNAU, Coimbatore, Rice diseases- online resource, IRRI, Phillippines.

• IRRI, Phillippines

Acknowledgements: