RESPONSE OF THE MOLLUSCICIDAL BERRY PLANT (PHYTOLACCA-DODECANDRA) TO DIFFERENT CLIMATIC AND EDAPHIC CONDITIONS

Clonal material from an imported Ethiopian cultivar (E44) and a local Zimbabwean cultivar (MSI) of the molluscicidal berry plant, Phytolacca dodecandra, was planted in eight ecological zones of Zimbabwe to asse ss the influence of different climatic and edaphic conditions on plant growth performance, berry yield, saponin content, and the molluscicid al potency of water extracts of the berries. The locations were at alt itudes ranging from 429 m to 1650 m above sea level and were chosen to represent the major ecological regions where the plant molluscicide w ould be required. The highest berry yield of 1057 g per plant was obta ined from the Ethiopian cultivar cultivated at an altitude of 1650 m w hile the highest berry yield from the Zimbabwean cultivar was 683 g pe r plant at an altitude of 1100 m. Saponin content and molluscidical po tency of berry extracts from the Ethiopian plants cultivated at all lo calities were higher than the Zimbabwean cultivar (P < 0.01). This ind icated the greater ecological adaptability of the Ethiopian variety fo r use in schistosomiasis control programmes. The addition of cattle ma nure at planting reduced the nutrient differences in inherent soil che mical properties on berry saponin content and molluscicidal potency. R egular irrigation during the study period prevented the previously dem onstrated water stress related increase in saponin content and potency of the berries from low rainfall areas. Saponin yield was highest (21 2 g per plant) in the Ethiopian cultivar at high altitudes. In lowland areas, however, this was highest for the Zimbabwean cultivar, notwith standing the good growth of the Ethiopian cultivar.