Pathogen
         Pyricularia oryzae (Teleomorph: Magnaporthe oryzae)

​

लक्षण

पातमा स–साना सेता टीका बीचमा भएका लाम्चिला खैरा थोप्ला देखा पर्दछन् । बाला मुन्तिरको डाँठको वरिपरी वा आँख्लामा खैरो रङ्ग भएको दाग पनि देखिन्छन् ।

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

​

​

​

​

​

​

​

​

​

​

​

 

Favorable Conditions
• Intermittent drizzles, cloudy weather, more of rainy days, longer duration of dew
high relative humidity (93-99 percent).
• Low night temperature (between 15-20°C or less than 26°C).
• Availability of collateral hosts and the excess dose of nitrogen.

 

Disease Cycle
The disease spreads primarily through airborne conidia since spores of the fungus present throughout the year. Mycelium and conidia in the infected straw and seeds are major sources of inoculum. Irrigation water may carry the conidia to different fields. The fungus also survives on collateral hosts viz., Panicum repens, Digitaria marginata, Brachiaria mutica, Leersia hexandra, and Echinochloa crusgalli.  Spores land on leaves, germinate, penetrate the leaf, and cause a lesion 4 days later; more spores are produced in as little as 6 days. Infections from spores arriving from a distance are termed primary infections. Primary infections generally result in a few widely scattered spots on leaves. Spores arising from the primary infections are capable of causing many more infections. This cycling is called secondary spread. Secondary spread is responsible for the severe epidemics of the blast in fields and localized areas.

 

 

 

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​