Field density and management of Pieris brassicae under the climatic conditions of the valley region of Manipur.
Population trend of Pieris brassicae Linn. was studied on cauliflower for two cropping seasons i.e. during 2013-15 in the experimental field of Life Sciences Department, Manipur University. Infestation of Pieris brassicae larvae began from last week of November and extended upto last week of April under the climatic conditions of Manipur with maximum density during February and March in both the cropping seasons. Simple correlation analysis between the pest's population and biotic and abiotic factors showed that none of the abiotic factors significantly influenced the density of pest's incidence in the late crop whereas biotic factors significantly influenced the density of pest. As many as 22 different insect species were found associated with cauliflower. In addition 7 plants extract such as Azadirachta indica, Phlogacanthus thyrsiflorus, Vitex trifolia, Centella asiatica, Ageratum conyzoides, Lantana camara, Parthenium hysterophorus etc were evaluated against Pieris brassicae under laboratory condition. The overall results revealed that all plant extracts have antifeedant property. Among the plant extracts Azadirachta indica, Vitex trifolia, Phlogacanthus thyrsiflorus, Parthenium hysterophorus and Lantana showed antifeedant property and may be used as bio-pesticides under the field conditions.