Severe infestation of cabbage butterfly, Pieris brassicae (Linnaeus) on six species of Brassica and effect of abiotic factors on its population dynamics

Impact of abiotic factors on population fluctuations of Pieris brassicae under agro-climatic conditions of Delhi during 2000–2001 rabi season was studied on six different species of Brassica and Eruca sativa. Pieris brassicae (L.) appeared during 9^th standard week and reached its peak (12 larvae/plant) in the 11 ^th standard week i.e. 3^rd week of march and thereafter the population declined but pest remained in the field till 13^th standard week. The mean temperature ranging from 17.6°C–23.80°C, relative humidity (65.3%), wind velocity (1.8 km/hr), and sunshine (7.3 hr), were found favorable for mass multiplication of Pieris brassicae. Correlation studies showed that the population was non-significantly and negatively correlated with maximum, minimum and mean temperature, while relative humidity, at morning and evening, mean showed significant negative correlation on population dynamics with (r) values −0.782, −0.933, −0.938, respectively. Wind velocity showed non-significant, negative correlation, but sunshine hours showed non significant positive correlation with population of cabbage butterfly.