Aqueous extracts of Euphorbia myrsinites L. (Euphorbiaceae) were tested for molluscicidal activity against Biomphalaria glabrata; LC50 values of 15.1 and 8.9 ppm were obtained for the stem and leaf extracts, respectively, which are within the WHO limit for an effective molluscicide. However, the extracts were found to be unstable at room temperature and the level of activity fell rapidly (about 50% after 7 days at 20 °C). Moreover, the extracts were shown to be cytotoxic and would thus, if used as a molluscicide, be potentially hazardous to the user. As a result, attempts were made to produce a simple formulation that was stable and easy to handle, thereby reducing the danger to the user, but which would decompose rapidly in aqueous solution after application, thus reducing any lasting ecological damage. A product based on spray drying the aqueous extract of the leaves and stems led to a preparation that, although slightly lower in activity than the original extract, was stable at room temperature for at least a year, but which decomposed in aqueous solution at a similar rate to the original extract.