Bacterial leaf blight
(Xanthomonas oryzae pv. Oryzae)

• Observed 1-3 weeks after transplanting
• Green water-soaked layer along the cut portion or leaf tip of leaves as early symptom
• Leaves wilt and roll up and become grayish green to yellow
• Entire plant wilt completely

• Water-soaked to yellowish stripes on leaf blades or starting at leaf tips with a wavy margin
• Leaves with undulated yellowish white or golden yellow marginal necrosis, drying of leaves back from tip and curling, leaving mid rib intact are the major symptoms.
• Appearance of bacterial ooze that looks like a milky or opaque dewdrop on young lesions early in the morning
• Severely infected leaves tend to dry quickly
• loss in grain yield may be up to 60%.

• To distinguish kresek symptoms from stem borer damage, the lower end of the infected seedling can be squeezed between the fingers.
• Yellowish bacterial ooze may be seen coming out of the cut ends.
• The cut portion can be observed against the light to see the bacterial ooze streaming out from the cut ends into the water.
•  After 1-2 hours, the water becomes turbid.

• The bacteria causing the disease are rods, 1.2 x 0.3-0.5 µm. They are single, occasionally in pairs but not in chains.
•  They are Gram negative, non-spore-forming, and devoid of capsules.
•  Their colonies on nutrient agar are pale yellow, circular, and smooth with an entire margin. They are convex and viscid.

Factors favouring disease development

• presence of weeds
• presence of rice stubbles and ratoons of infected plants
• presence of bacteria in the rice paddy and irrigation canals
• warm temperature(25-30° C), , high humidity, rain and deep water.
• Severe winds, which cause wounds, and over fertilization are suitable factors for the development of the disease.
• Irrigation water and splashing or windblown rain can disseminate the bacterium from plant to plant.
• The use of trimming tools for transplanting and by handling during transplanting can also trigger new infection.

• Seed treatment with bleaching powder (100g/l) and zinc sulfate (2%) reduce bacterial blight.
• Seed treatment - seed soaking for 8 hours in Agrimycin (0.025%) and wettable ceresan (0.05%) followed by hot water treatment for 30 min at 52-54oC;
•  seed soaking for 8 hours in ceresan (0.1%) and treat with Streptocyclin (3g in 1 litre);
• Spray neem oil 3% or NSKE 5%
• Spray fresh cowdung extract for the control of bacterial blight. Dissolve 20 g cowdung in one litre of water; allow to settle and sieve. Use supernatant liquid. (starting from initial appearance of the disease and another at fortnightly interval)

• Grow Tolerant varieties (IR 20 IR 72,PONMANI , TKM 6).
• Secure disease free seed
• Grow nurseries preferably in isolated upland conditions
• Avoid clipping of seedlings during transplanting.
• Balanced fertilization, avoid excess N - application
• Skip N - application at booting (if disease is moderate)
• Drain the field (except at flowering stage of the crop)
• Destruction of weeds and  collateral hosts
• Avoid flow of water from affected fields
•  Maintain proper plant spacing

• Seed treatment with bleaching powder (100g/l) and zinc sulfate (2%) reduce bacterial blight.
• Seed treatment - seed soaking for 8 hours in Agrimycin (0.025%) and wettable ceresan (0.05%) followed by hot water treatment for 30 min at 52-54oC;
•  seed soaking for 8 hours in ceresan (0.1%) and treat with Streptocyclin (3g in 1 litre);
• Spray Streptomycin sulphate + Tetracycline combination 300 g + Copper oxychloride 1.25kg/ha. If necessary repeat 15 days later.
• Application of bleaching powder @ 5 kg/ha in the irrigation water is recommended in the kresek stage.
•  Foliar spray with copper fungicides alternatively with Strepto-cyclin (250 ppm) to check secondary spread.