In the present study, pesticidal activity of lectin against different life stages of major groundnut defoliator Spodoptera litura has been studied under in vitro condition. Lectin was isolated frompulp of banana and partially purified by silica gel and mannose – sepharose 4B affinitychromatography and the total yield of affinity purified lectin was about 50 mg. Bio assay was studied against second and third instars of S. litura which reveals both the instars were susceptibleto the lectin in concentration dependent manner. Distinct effect on lethal concentration 50 (LC 50), lethal time 50 (LT 50) against the larval instars, pupal, adult emergence and adult longevity was observed.