Introduction

Various species of aquatic snails act as intermediate host of trematode Fasciola hepatica and Fasciola gigantica, which are causing fascioliasis and schistosomiasis diseases in both human as well as in vegetarian mammals as sheep, goat and cattles are wide spread in the world especially in developing countries (Haridy et al., 2002, Engles et al., 2002 and Sukumaran et al., 2004, Parsak et al., 2007, Michael Asrat et al., 2007, Santiago 2009, Singh et al., 2009). Livestock diseases are widely distributed and one of the major causes of livestock mortality, and sub-optimal productivity in all agro-ecological zones of the country (EARO, 2000) is diminishing the benefit of their high reproductive performance. Species of the Lymnaidae family as Lymnaea acuminata are known for their role as intermediate hosts in the life cycle of F. gigantica or F. hepatica. These snails’ causes enormous production losses in these animals reported from various parts of the world (Griffiths, 1957; Fabiyi, 1986; Babalola et el., 1976; Diaw et al., 1998; Rahman et al., 1972; Edney and Muchlis, 1962 and Srikipjakarn, 1986). The disease is acquired mostly by consumption of watercress-like vegetables or drinking water contaminated with metacercariae (Parsak et al., 2007). The absence of appropriate host/snails protects regions from fascioliasis and schistosomiasis. This is accompanied by using appropriate method. Various attempts to control them have failed (Panigrahi and Raut, 1994), although some synthetic molluscicides are giving encouraging results (Godan 1983, Agarwal and Singh, 1988), their use is being discouraged because increasing concern over the possibility of snail resistance to these compounds and their toxicity in non-target organisms, have given a new impetus to the study of plant molluscicides (Duncan, 1987; Sharma et al., 2009). Plant origin molluscicides have gained greater importance since it is believed that natural products are ecologically sound and culturally more acceptable than synthetic ones (Sharma et al., 2009). It has been observed that molluscicidal activity of latex, stem bark and leaf of Jatropha gossypifolia and binary, tertiary combinations of Jatropha gossypifolia latex powder with taraxerol, rutin, betulin and ellagic acid are potent molluscicides against freshwater snail Lymnaea acuminata and Indoplanorbis exustus in earthen cemented pond (Yadav, and Singh 2006).

There are various literatures are available on the molluscicidal activity of different pesticides in the laboratory condition, but a very little literature are available in the natural condition. In natural condition many factors such as temperature, sunlight, adsorption by soil particles etc. influences on toxicity and toxicant degradation. So without evaluation of these plant extract in field condition, no one can get effectual result. In this investigation molluscicidal activity of two common medicinal plant Lantana indica and Alstonia scholaris was study in the pond against freshwater snail Lymnaea acuminata.

Lantana indica is used as a sudorific, intestinal antiseptic, diaphoretic, and in treatment of tetanus and rheumatism and malaria in Indian medicine (Chopra et al., 1999, Ghisalberti, 2000, Ojha and Dayal, 1992) Its different parts are also used as traditional medicine for the treatment of various human ailments such as ulcers, eczema eruptions, and malaria (Kirtikar and Basu, 1961, Sastri, 1962, Begum et al., 1995).   

Alstonia scholaris various parts are used in headache, pain in legs and loins, rheumatism, haemoplegia, cholera, bronchitis, phthisis and asthama, pleurisy, pneumonia and lactation complaints. Milky latex is applied to ulcers, vitiated conditions of vata and otalgia (Kirtikar and Basu, 1980, Nadkarni and Nadkarni, 1976), sores, toothache, tumours and in rheumatic pain, mixed with oil and dropped into the ear, it relives earache. Bark is used in curing gastrointestinal troubles, malaria, diarhhoea, dysentery, snakebite, skin diseases, heart diseases, asthama and to stop bleeding of wounds. Sap gum and roots are used in tumors and cancer.