Herbicidal Activity of Thymbra capitata (L.) Cav. Essential Oil

Abstract

The bioherbicidal potential of <i>Thymbra capitata</i> (L.) Cav. essential oil (EO) and its main compound carvacrol was investigated. In in vitro assays, the EO blocked the germination and seedling growth of <i>Erigeron canadensis</i> L., <i>Sonchus oleraceus</i> (L.) L., and <i>Chenopodium album</i> L. at 0.125 µL/mL, of <i>Setaria verticillata</i> (L.) P.Beauv., <i>Avena fatua</i> L., and <i>Solanum nigrum</i> L. at 0.5 µL/mL, of <i>Amaranthus retroflexus</i> L. at 1 µL/mL and of <i>Portulaca oleracea</i> L., and <i>Echinochloa crus-galli</i> (L.) P.Beauv. at 2 µL/mL. Under greenhouse conditions, <i>T. capitata</i> EO was tested towards the emergent weeds from a soil seedbank in pre and post emergence, showing strong herbicidal potential in both assays at 4 µL/mL. In addition, <i>T. capitata</i> EO, applied by spraying, was tested against <i>P. oleracea</i>, <i>A. fatua</i> and <i>E. crus-galli</i>. The species showed different sensibility to the EO, being <i>E. crus-galli</i> the most resistant. Experiments were performed against <i>A. fatua</i> testing <i>T. capitata</i> EO and carvacrol applied by spraying or by irrigation. It was verified that the EO was more active at the same doses in monocotyledons applied by irrigation and in dicotyledons applied by spraying. Carvacrol effects on <i>Arabidopsis</i> root morphology were also studied.