Herbicidal value of essential oils from oregano-like flavour species

Chemical composition and phytotoxicity of oregano, marjoram and Thymus mastichina essential oils against Portulaca oleracea L., Lolium multiflorum Lam. and Echinochloa crus-galli (L.) Beauv. has been investigated. Seventy-seven compounds reaching 97.3% and 99.4% were identified by gas chromatography-mass spectrometry. Carvacrol (60.42 +/- 0.07%), p-cymene (15.52 +/- 0.02%) and -terpinene (5.19 +/- 0.02%) were the main compounds in oregano essential oil, whereas large amounts of 1,8-cineol (59.59 +/- 0.85%, 49.49 +/- 0.37%), linalool (13.05 +/- 0.04%, 5.66 +/- 0.01%) and -terpineol (3.36 +/- 0.10%, 5.59 +/- 0.01%), followed by -pinene (4.35 +/- 0.39, 5.54 +/- 0.01%) and -pinene (4.11 +/- 0.53, 4.28 +/- 0.01%) were found, respectively, in marjoram and T. mastichina essential oils. Oregano essential oil completely inhibited seed germination and seedling growth at all concentrations assayed (0.125-1 mu LmL(-1)), whereas marjoram and T. mastichina essential oils only showed significant effects in hypocotyl and/or hypocotyl+radicle length depending on the weed and dose. [GRAPHICS] .