The Acacia bark phytotoxic potential: a non-synthetic bio-herbicide

C. Chemetova, H. Ribeiro, A. Fabião, J. Gominho
A natural technique to control weed emergence and decrease the use of synthetic herbicides could be the application of phytochemical substances with phytotoxic effects from Acacia bark. In Mediterranean area, A. melanoxylon and A. dealbata bark are an abundant waste material from non-native tree species control actions, requiring suitable disposal. The presence of phytotoxic substances in young harvested biomass is greater than in mature plant tissues, thus for organic substrates formulation aging treatment is only effective (phytotoxicity reduction after 8 weeks) for A. melanoxylon mature bark, which potentiate young bark for different valorization. This study explores A. melanoxylon and A. dealbata bark extracts from young debarked trees, regarding their bio-herbicide effect on germination and development of cress seeds. Extraction conditions were performed under fixed time (t: 45min) and a maximum temperature of 120°C, using the following solvents: ethanol, water and an equal volume of ethanol:water. The extract yield was greater in water extracts (40 g dry extract L‑1), followed by 50% ethanol:water (36 g dry extract L‑1) and ethanol (28 g dry extract L‑1). In water extract essay, the extract yield remained constant even after bark percentage gradual reduction over the extraction ratio conditions (liquid:bark ratio from 1:5, 1:10 and 1:15), suggesting a possible final liquor saturation. However, all bark extracts inhibited the tested seed growth (root index KLEINERDAN8%) compared to deionized water control (root index = 100%). The bio-herbicide activity of water soluble Acacia bark phytochemical substances increases its phytotoxic effect as extract concentration increase.
Chemetova, C., Ribeiro, H., Fabião, A. and Gominho, J. (2021). The Acacia bark phytotoxic potential: a non-synthetic bio-herbicide. Acta Hortic. 1305, 103-108
DOI: 10.17660/ActaHortic.2021.1305.15
bark extracts, A. melanoxylon, A. dealbata, phytochemicals concentration, seed inhibition

Acta Horticulturae