Identification of Pathogen:
- H. oryzae produces brown septate mycelium. Conidiophores may arise singly or in small groups. They are geniculate, brown in colour.
- Conidia are usually curved with a bulged center and tapered ends. They are pale to golden brown colour and are 6-14 septate.
- The perfect stage of the fungus is C. miyabeanus. It produces perithecia with asci containing 6-15 septate, filamentous or long cylinderical, hyaline to pale olive green ascospores.
- These breakdown the protein fragment of cell wall resulting in partial disruption of integrity of cell.
Favourable Conditions:
- Temperature of 25-30 C with relative humidity above 80 per cent is highly favourable. Excess nitrogen aggravates the disease severity.
Mode of Spread and Survival :
- Infected seeds and stubbles are the most common source of primary infection. The conidia present on infected grain and mycelium in the infected tissue are viable for 2 to 3 years.
- Airborne conidia infect the plants both in nursery and in main field.
- The fungus also survives on collateral hosts like Leersia hexandra and Echinochlora colonum.
Management:
- Field sanitation-removal of collateral hosts and infected debris from the field
- Use of slow release of nitrogenous fertilizers is advisable.
- Grow resistant and moderately resistant varieties like CO 51, CO 52, CO 53, CO 55, CO 56, ASD 18 and IR 64.
- Use disease free seeds.
- Treat the seeds with Thiram or Captan at 4 g/kg. Spray the nursery with Edifenphos 40 ml or Mancozeb 80 g for 20 cent nursery.
- Spray the crop in the main field with Edifenphos 200 ml or Mancozeb 500 g when grade reaches 3. If needed repeat after 15 days.
Source of information:
- AICRIP rice, TNAU, Coimbatore Rice diseases- online resource, IRRI, Phillippines.
Acknowledgements:
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