The Molluscicidal Activity of Apodytes Dimidiata E. Meyer Ex Arn (Icacinaceae), Gardenia Thunbergia L.f. (Rubiaceae) and Warburgia Salutaris (Bertol. F.) Chiov. (Cannelaceae), Three South African Plants

Mollusciciding is still considered the most important means of control of schistosomiasis where the volume of water per caput is small. In rural communities the cost of synthetic molluscicides and/or chemotherapy prohibits their use. Plant molluscicides, applied as crude aqueous suspensions are the source of cheap, effective and environmentally acceptable alternatives. Further, infected communities are likely to accept the use of local indigenous plants, particularly if they have more than one local application, since they are familiar with their properties and growth characteristics. In this study the activity of crude aqueous suspensions of six South African plants were assessed. Suspensions of leaf material were bioassayed for activity using Bulinus africanus. Probit analysis was used to calculate LD50 and LD90 values. Three species would receive priority for further investigations of extract stability and toxicology, i.e. comprehensive evaluation. For this purpose species were ranked on toxicity as aqueous suspensions, the highest toxicity level previously recorded in the literature, and on their cultivation potential. Ranks for each plant were summed and Gardenia thunbergia, Apodytes dimidiata, and Warburgia salutaris had the lowest cumulative rankings (i.e. the highest molluscicidal activity and greatest cultivation potential).