The environmental toxicity of Dicerothamnus rhinocerotis and Galenia africana

Abstract

Over the years the use of pesticides has greatly increased. This in turn has lead to concern about the adverse effects that the pesticides may have on non-target organisms in the environment. Due to increasing awareness there is great pressure to reduce the use of synthetic pesticides. An alternative to the use of synthetic pesticides is the exploitation of natural botanical products with pesticidal potential.Dicerothamnus rhinocerotis and Galenia africana are plants, indigenous to South Africa, with fungicidal properties against a fungal pathogen that causes grey-mould rot on a wide range of agricultural produce. In this study a series of acute toxicity tests were conducted to estimate the potential environmental effect of D. rhinocerotis and G. africana. The acute toxicities of the plants were determined using the species Daphnia pulex, Selenastrum capricornutum, Vibrio fischeri andPoecilia reticulata as bio-indicators. Results obtained showed that G. africana had higher toxicity units than D. rhinocerotis, thus showing that G. africana is more toxic to the aquatic environment compared to D. rhinocerotis. Key words: Pesticides, Galenia africana, Dicerothamnus rhinocerotis, acute toxicity.