The insecticidal activities of hexane, ethyl acetate, methanol and water extracts of lichen, Roccella montagnei Bél. emend. Awas. were assayed against polyphagous insect, Helicoverpa armigera (Hübner). Among the different crude extracts tested, the pupation was nil in methanol (1%) and hexane extract (5%), which was on par with aqueous extract (5%). The formulation of water extract of R. montagnei is better compared to other solvent extracts, as potential antipest agent against H. armigera.