Study on population build up of rice leaf folder, Cnaphalocrocis medinalis (Guenee) in relation to weather factors

Populations of rice leaf folder, Cnaphalocrocis medinalis (Guenee) were studied in basmati rice. The observations recorded from second fortnight of July (29th standard week) to harvest of the crop. The pest population recorded as number of larvae per hill ranged from 0.50 to 5.10 larvae. The larval population was low during July to fourth week of August and varied between 0 to 1.90 larvae per hill. The pest population increased from end of August to start of September and reached its peak (5.10 larvae/hill) during 38th standard week i.e. second fortnight of September. All the weather parameters showed negative correlation with larval population such as maximum (r=-0.0909) and minimum (r=-0.3796) temperature. Negative correlation was also found with relative humidity (r=-0.1146) and rainfall (r=-0.5108) during crop season i.e. Kharif 2011.