S14 - Session O3 - Essential oils as alternative of synthetic herbicides for horticultural crops

Authors: Bérénice Foncoux *, Sofiene Ben kaab, Simon Dal Maso, M. Haïssam Jijakli

Weed management programs are often more expensive for horticultural crops than agricultural ones. The lower efficiency of herbicides for such crops, the limited number of herbicides and the increasing cost of labour lead to a need for innovative and effective herbicides. With the actual controversy of synthetic herbicides, efficient, sustainable and environmentally-friendly herbicides are highly sought-after. In this context we studied the promising alternative that are essential oils, their effects on weeds in greenhouse conditions and in the field as well as their modes of action. The greenhouse trials showed that the formulated essential oil (EO1) has a high herbicidal activity against Trifolium incarnatum , and Lolium perenne . In order to understand the mode of action of essential oil, treated leaves were analysed in the lab. Results showed that the EO1 decreases the water content by around 63% for T. incarnatum against 36% for L. perenne after 5 hours. In the same line, EO1 affects membrane integrity and increases the malondialdehyde content in leaves after 5 hours. The observation by electron microscopy showed that after 30 min of treatment by EO1, significant damage is already visible. Field trials were also performed in 2019, 2020 and 2021 to study the herbicidal effect of essential oils against several species of weeds. EO1 was applied twice against four monocotyledons and twelve dicotyledons that were sown in Belgium and had reached the BBCH stage 15-30. The results showed that EO1 was efficient against all dicotyledons on par with the commercially available positive control and was less efficient against monocotyledons. Based on the strong weed suppressive ability of this essential oil and its mode of action, it offers interesting possibilities as an effective natural environment-friendly approach for weed management in horticulture.