Use оf Essential Oils аs Natural Herbicides

Essential oils are complex mixtures of volatile compounds, mainly terpenes and phenylpropanoids, particularly abundant in aromatic plants. In the last decades, there are many reports about herbicidal potential of essential oils. An initial step to assess their herbicidal activity is to determine their effect on seed germination and seedling growth. The present review summarizes the methods for assess the effects of essential oils on seed germination and seedling growth. The advantages and disadvantages of using essential oils for weed control are discussed. Also important conclusions regarding their application as natural herbicides are drawn. Essential oils obtained from plant species from the families Myrtaceae, Pinaceae, Lauraceae, Poaceae, Lamiaceae, Asteraceae, Cupressaceae, Apiaceae and etc. are determined as promising for weed control. Based on some essential oils derived from lemongrass, cloves and cinnamon, commercial weed control products have already been developed. The studies in Bulgaria have been mainly focused on the effect of extracts on seed germination. However, it was found that essential oils of Bulgarian species Origanum vulgare subsp. hirtum (Link) Ietsw, Thymus longidentatus (Degen & Urum.) Ronniger., Thymus moesiacus Velen, Micromeria dalmatica Benth. exhibit strong inhibitory activity on seed germination of weeds. The main components of essential oil identified for each species were respectively carvacrol for O. vulgare subsp. hirtum, citral isomers: neral and geranial of T. longedentatus, α-terpinyl acetate of T. moesiacus, piperitone oxide, carvacrol, β-pinene of M. dalmatica. The presented data show that the essential oils have strong inhibitory effects on germination and seedling growth of weeds and this makes them a promising source for production of natural herbicides.