Abstract
In an attempt to search for natural pesticides, crude extracts of seven plant species (Bauhinia purpurea, Caesalpinia gilliesii, Cassia fistula, Cassia senna, Chrysanthemum frutescens, Euonymus japonicus and Thespesia populnea var. acutiloba) were evaluated against Sclerotium rolfsii, the causative fungus of damping-off, under laboratory and greenhouse conditions. Gas chromatography-mass spectrometry analysis was performed to identify possible biologically active components (tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, phytol, linalool, 1,8 cineole and 9, 12, 15 octadecanoic acid) from the plant extracts most effective against S. rolfsii. Laboratory experiments indicated that leaf extracts of T. populnea var. acutiloba and Chrysanthemum frutescens were most effective against S. rolfsii. Greenhouse experiments confirmed that T. populnea var. acutiloba and Chrysanthemum frutescens extracts were most effective against the damping-off pathogen, either by coating or soaking of sugar beet seeds. None of the extracts tested produced phytotoxic effects on sugar beet leaves, even at the highest concentration applied. The most effective plant extracts showed low toxicity in rats relative to controls with respect to histological tests. The extracts assayed represent a potentially safe control method for damping-off disease in sugar beet.