Evaluation of botanicals for pesticidal activity against tobacco caterpillar, Spodoptera litura (F.)

Abstract

Spodoptera litura (F.) (Lepidoptera: Noctuidae) is a polyphagous pest of various oilseed crops like soybean, groundnut, castor and sunflower. Usage of chemical pesticides will often lead to pest resistance, pest resurgence and environment linked problems. Hence, exploring the pesticidal potential of different botanicals for its management is an eco-friendly option. A bioassay experiment in completely randomized design was conducted to study the pesticidal activity of various botanicals (Adhatoda vasica L., Calotropis gigantea L., Melia azedarach Cav., Murraya koenigii L., Pongamia pinnata L. and Vitex negundo L.) against S. litura in castor. Extracts were prepared from various botanicals using acetone and methanol and evaluated against third instar larvae of S. litura at 24, 48 and 72 hrs with 250, 500, 750 and 1000 ppmconcentrations under laboratory condition. Total phenolic contents and phytocomponents of the botanicals by GC-MS were also studied. Results of the present study indicated that the maximum percentage mortality of third instar larvae of S. litura was observed with methanolic extracts of M. azedarach and P. pinnata in 1000 ppm concentration after 72 hours, which was followed by M. koenigii. Higher total phenol content was recorded with M. koenigii, M. azedarach and P. pinnata. The GCMS study revealed the presence of squalone, a triterpenoid compound in M. azedarach and P. pinnata. This study suggests that, bio-pesticidal potential of M. azedarach and P. pinnata was due to the presence of phenolic and triterpenoid compounds resulted in higher larval mortality of S. litura.