Bacterial leaf blight: Xanthomonas oryzae pv. oryzae (Ishiyama) Swing et. al.
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
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:
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.
- 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