Bioecology and management of rice leaf folder Cnaphalocrocis medinalis Guenee infesting paddy in Himachal Pradesh

Abstract

newline The present investigation entitled Bioecology and management of rice leaf folder, Cnaphalocrocis medinalis (Guenee) infesting paddy in Himachal Pradesh was undertaken in the Department of Entomology, CSKHPKV, Palampur and Rice and Wheat Research Centre, Malan during 2014-2016. Under laboratory conditions, C. medinalis completed three generations from August to mid-December. The life cycle of C. medinalis consisted of four distinct stages viz., egg, larva, pupa and adult, each having an average duration ranging between 3.70-4.50, 17.50-20.50, 7.00-7.50 and 6.40-7.40 (female); 2.50-3.30 (male), respectively, during different generations. The fertility parameters worked out for first, second and third generation resulted in the net reproductive rate (R0) of 29.16, 17.94 and 17.72 female eggs per female with the corresponding true generation time of 37.06, 37.99 and 39.38 days, respectively. The intrinsic rate of increase (rm) was maximum in the first generation (0.091) and minimum in the third generation (0.073). The field collected adults of last generation when reared under laboratory conditions to study the survival of pest, failed to lay eggs. However, a few individuals of C. medinalis larvae survived in winter till January on paddy plants and weeds and a limited feeding was observed during this period. Survey for the incidence of C. medinalis and its associated natural enemies in four locations viz., Sundernagar, Nurpur, Jogindernagar and Palampur of Himachal Pradesh was conducted during 2015 and 2016 at different time intervals. The pest appearance was noticed in the second fortnight of July at Nurpur, Palampur and Jogindernagar. Whereas, at Sundernagar, the pest activity initiated during first fortnight of July and population of adults was at its peak in the first fortnight of September in all the four locations. From the correlation studies between adult catch and abiotic factors, it was concluded that the temperature (maximum and minimum) favours the C. medinalis build-up. However, RH (maxim