Pathogen:
- The mycelium is hyaline to olivaceous and septate.
- Conidia are produced in clusters on long septate, olivaceous conidiophores.
- Conidia are pyriform to ellipsoid, attached at the broader base by a hilum. Conidia are hyaline to pale olive green, usually 3 celled.
- The perfect state of the fungus is M. grisea producing perithecia. The ascospores are hyaline, fusiform, 4 celled and slightly curved.
Survival and Mode of spread:
- The fungus survives on collateral hosts viz., Panicum repens, Digitaria magrginata, Brachiaria mutica, Leersia hexandra and Echinochloa crusgalli.
- Mycelium and conidia in the collateral hosts, straw and seeds are major sources of primary inoculum.
- The secondary spread takes place through airborne conidia since spores of the fungus present throughout the year. Irrigation water may carry the conidia to different fields.
Favourable Conditions:
- Intermittent drizzles
- Cloudy weather
- High relative humidity (93-99 per cent)
- Low night temperature (between 15-20 C or less than 26 C
- Availability of collateral hosts
- Application of excess nitrogen
Management:
- Grow resistant and moderately resistant varieties like CO47, CO 51, CO 52, CO 53, CO55, CO56, ASD 18 and IR64.
- Remove and destory the weed hosts in the field bunds and channels.
- Treat the seeds with Captan or Thiram or Carbendazim or Tricyclazole at 2 g/kg or Bacillus subtilis @ 10g/kg of seed.
- Spray the nursery with Carbendazim 50 WP @ 25 g or Edifenphos 50 EC @ 25 ml for 20 cent nursery.
- Foliar spray the main field with edifenphos 200 ml or carbendazim 100 g or tricyclazole 75 WP @ 200 g or iprobenphos (IBP) 200 ml /acre or azoxystrobin + difenoconazole 100 ml/acre when initial symptoms are noticed.
Source of information:
- AICRIP Rice, TNAU, Coimbatore Rice diseases- online resource, IRRI, Phillippines.
Acknowledgements:
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