Population dynamics of rice stem borer and rice leaf folder

Abstract

A field experiment was carried out for two years to study the population dynamics of rice stem borer Scirpophaga incertulas (Walker) and leaf folder Cnaphalocrocis medinalis (Guenee). The results revealed that the deadheart (DH) symptom appears from 30th standard week with a mean incidence of 2.18 (2018) and 4.32% (2029). The white earhead (WEH) first appeared on 40th standard week with a mean incidence of 6.93 (2018) and 5.29% (2019), respectively. In case of rice leaf folder, the damage appeared during 30th standard week- 4.25% (2018) and 5.78% (2019). The correlation coefficients revealed that maximum (r=0.525*, 0.510*) and minimum temperature (r=0.487, 0.427), morning (r=0.285, 0.033) and evening relative humidity (r=0.233, 0.226) had a positive relationship with stem borer damage. With leaf folder, maximum (r=0.527*, 0.590*) and minimum temperature (r=0.849**, 0.853**), morning (r=0.244, 0.458) and evening relative humidity (r=0.518*, 0.269) and wind velocity (r=0.356, 0.361) had significant positive relationship.