Bacterial leaf blight: Xanthomonas oryzae pv. oryzae (Ishiyama)   Swing et. al. (Pseudomonadales: Pseudomonadaceae) Kannada Name: Dundanu Macchhe Roga Period of occurrence: Tillering to heading stage Extent of yield loss: 6-60% in extreme cases Alternate hosts: Grasses (Leersia spp.  & Cyperus rotundus) Favorable conditions for the pathogen Combinations of rainy weather, dull windy days and an atmospheric temperature of 22-26°C High doses of N Close planting Mode of transmission/dissemination: Rain splashes (wind borne rain) coupled with wind injuries to rice leaves, irrigation water. Source of inoculum: Seed, Soil or Plant debris, Alternate hosts. Symptoms: The disease occurs in two phases Kresek or wilt phase: Appears during active tillering stage Death of the tillers and hill resembles the damage of dead heart caused by stem borer.

Kresek symptom Seedling blight

Bacterial Blight of Paddy

Leaf blight phase:

• Appears during maximum tillering to heading stage. 
• The leaf margins become water soaked and turns yellow to straw colour in a wavy pattern. Later, disease spreads downwards and inwards of leaf blade causing drying and death of the leaf.
• On the surface of affected leaves, bacterial ooze that looks like a milky or opaque dew drop may be observed in the early morning.
• Panicle become sterile and unfilled poor quality grains.

Bacterial ooze test:

When the infected leaves are cut into small bits and put into water in a glass tube, the water becomes turbid and yellowish after the lapse of 30-60 minutes.  This turbidity is due to the release of bacterial cells into water from the cut ends of the leaf bits.

Preventive measures:

• Use of resistant varieties - Ajaya, Asha, Biraj, CO-43, Gobind, IR-64,  Janaki, PR-4141, Radha, Sona Mahsuri, Sujata, Suraj, Swarna, Udaya.
• Balanced fertilizer application - Split application of N
• Reduce the disease spread by careful handling of seedlings during transplanting, maintaining shallow water in nurseries, providing good drainage during severe flooding.
• Reduce the amount of inoculum through clean cultivation and drying the fallow fields
•  Remove collateral weed hosts from bunds and channels.
•  Use only disease free seedlings.
•  Avoid excess nitrogen. 
•   Apply N  in three split doses, 50% basal, 25% in tillering phase and 25%N in panicle initiation stage

Chemical control: University of Agricultural Sciences, Dharwad.

• Seed treatment with 0.1 g Streptocycline and 0.1 g Copper Sulfate or 0.3 g Agrimycin-100 and 0.1 g Copper Oxychloride in one liter of water for 20 minutes
• Foliar spray of 0.05 g Streptocycline and 0.05 g Copper Sulfate