Reviews on Phytotoxic Effects of Essential Oils and Their Individual Components: News Approach for Weeds Management

Currently, the use of synthetic chemicals to control weeds raises several concerns related to environment and human health. An alternative is to use natural products that possess good efficacy and are environmentally friendly. Among those, essential oils have been extensively tested to assess their herbicidal properties as valuable natural resource. The essential oils whose phytotoxic activities have been demonstrated, as well as the importance of the synergistic effects among their components are the main focus of this review. Essential oils are volatile mixtures of hydrocarbons with a diversity of functional groups (ketones, ether, ester, alcohol, phenol, aldehyde ...) and their herbicidal activity has been linked to the presence of monoterpenes and sesquiterpenes. However, in some cases, these chemicals can work synergistically, improving their effectiveness. Among the plant families with promising essential oils used as herbicide, Lamiaceae, Myrtaceae, Asteraceae and Anacardiaceae are the most cited. Individual compounds present in these mixtures with high activity include α-pinene, limonene, 1,8-cineole, carvacrol, camphor and thymol. Finally, although from an economical point of view synthetic chemicals are still more frequently used as herbicide than essential oils, these natural products have the potential to provide efficient and safer herbicide for humans and the environment. Keys words: essential oils, terpenes, phytotoxicity, allelopathy, terpenes, chemotypes.