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Bacterial leaf blight of rice

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
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