Agricultural aromatherapy: Lavender oil as natural herbicide

Elena Sturchio of the National Institute of Health and Safety at Work in Rome and colleagues there and at the Department of Infectious and Tropical Diseases, and the Department Crop Production, at Tuscia University, in Viterbo, have investigated the inhibitory effects on weed growth of aromatic oils, or mixtures of phytochemicals, from plants such as lavender, Lavandula officinalis.

Essential oils, are as the name suggests, often the plant's "essence" in terms of odour. Essential oils are complex chemical mixtures of natural products made by the plant for its own purposes, including terpenes, alcohols, aldehydes and phenols. Indeed, several plant essential oils are present as natural inbuilt herbicides and pesticides.

Synthetic pesticides and herbicides have been in common use for decades and have protected crops from parasites, insects, bacteria, viruses, fungi, and eliminated weeds. However, by virtue of their design, these substances are toxic and in some cases thought to be carcinogenic. Their incorrect use or inadvertent exposure have been the focus of numerous studies on animal and human health, the results of which have led to serious initiatives to find alternative approaches to pest and weed control.

Other researchers have investigated the potential of essential oils from cinnamon plants, and peppermint to prevent seed germination of some weed species found in the Mediterranean region.

Sturchio and colleagues have investigated the effects of lavender oil on root growth in a plant, Vicia faba in trials. This weed has large chromosomes and so was also amenable to studies in the laboratory that investigated the genetic toxicity of the essential oil on the weed. Their analysis showed the oil to be effective at killing the weed even at low concentration. Moreover, the oil affects growth of soil microbes and fungi involved in crop growth.

The team concludes that, "Essential oils could be useful as potential bioherbicides as an alternative strategy to the chemical remedy." They add that, "The use of phytochemicals permits the development for more sustainable agriculture at low environmental impact. Further studies are now needed to evaluate use of such oils "in the field".

The team points out that the oils would most likely be used either before planting or prior to transplantation of seedlings, so the essential oil would not have toxicity effects on the crop itself. Sturchio adds that, "essential oils are not accumulated in the environment, because of their low persistence due to the easy degradation by microbial and enzyme activity. This aspect could represent an advantage compared to the bioaccumulation of chemicals on soil."