Abstract: In this study the molluscicidal activity of methanolic extract of stem bark of Lantana indica (family- Verbenaceae) and Alstonia scholaris (family- Apocynaceae) singly or in binary mixtures against freshwater snail Lymnaea acuminata were evaluated in pond. This snail is the intermediate hosts of liverfluke, Fasciola hepatica and Fasciola gigantica, which causes endemic fascioliasis in cattle and livestock in northern part of India.  The toxic effect of both the plants extracts was time as well as dose dependent. The LC₅₀ values decreases as exposure period increases. Thus LC₅₀ values of methanol extract of stem bark of Lantana indica decreases from 41.28 mg/L (24h) to 14.73 mg/L (96h) and in the case of Alstonia scholaris LC₅₀ value decreased from 55.19 mg/L (24h) to 23.20 mg/L (96h). Binary mixture of both the plant extract also shows similar trends but their toxicity was about 2.42 times more toxic than individual extract.

Exposure of sub-lethal doses of both the plant extracts also significantly alter the total protein, total free amino acids, glycogen, and nucleic acids levels and activity of enzyme protease in time and dose dependent manner in nervous and hepatopancreas tissue of snail Lymnaea acuminata. Seven days withdrawal of treatment, there was significant (p<0.05) recovery in all the biochemical parameters in both the tissues of snail Lymnaea acuminata.

Keywords: Lantana indica, Alstonia scholaris, Lymnaea acuminata, methanol extract,