Impact of Solvents and Extraction Methods on the Insecticidal Activity of Sesbania grandiflora L. Leaf Extracts against Diamondback Moth, Plutella xylostella

Diamond back moth Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a notorious pest of cruciferous crops causing extensive damage. The present study compares the insecticidal activity of Sesbania grandiflora extracts in hexane, ethyl acetate, and ethanol obtained from two extraction methods: Soxhlet and cold maceration against P. xylostella. Soxhlet extraction by all the solvents showed a distinct effect on larval mortality, adult emergence, and the growth and development of second-instar larvae than cold maceration extraction. Soxhlet ethanolic extract at 5% had significantly better insecticidal activity than cold maceration, with complete larval mortality. The antifeedant index was also higher in ethanol extract, followed by ethyl acetate and hexane extract. However, there was no significant variation in the developmental period. Thus, Soxhlet ethanolic extract of S. grandiflora is concluded to have a promising insecticidal activity on P. xylostella.