In vitro evaluation of essential oils from Mediterranean aromatic plants of the Lamiaceae for weed control in tomato and cotton crops

We studied the potential allelopathic activity of seven essential oils against two crops (tomato and cotton) and 5 weeds (Amaranthus retroflexus, Echinochloa crus-galli, Oryza sativa, Portulaca oleracea and Setaria verticillata). The essential oils examined originated from Lavandula stoechas, L. angustifolia, Mentha spicata, Origanum onites, O. vulgare ssp. hirtum, Salvia fruticosa and S. pomifera. In in-vitro experiments, we determined the effect of these essential oils and their constituents on seedling emergence and growth of target species. The oils of M. spicata, O. onites and O. vulgare ssp. hirtum severely affected both weed and crop species. Among the weeds, A. retroflexus was most sensitive, whereas O. sativa and E. crus-galli were least sensitive. Cotton proved the most sensitive of all species. The essential oils that originated from Lavandula and Salvia spp. showed good efficacy against A. retroflexus and P. oleracea, without severely affecting the tomato, hence, they have a high potential to be used as selective herbicides for weed control in tomato fields.