Ginger and Turmeric Essential Oils for Weed Control and Food Crop Protection

Ginger and turmeric are two food ingredients that are in high demand due to their flavor and positive effects on health. The biological properties of these spices are closely related to the aromatic compounds they contain. The chemical compositions of their essential oils and their in vitro phytotoxic activity against weeds (Portulaca oleracea, Lolium multiflorum, Echinochloa crus-galli, Cortaderia selloana, and Nicotiana glauca) and food crops (tomato, cucumber, and rice) were studied. Forty-one compounds, accounting for a relative peak area of 87.7% and 94.6% of turmeric and ginger essential oils, respectively, were identified by Gas Chromatography–Mass Spectrometry analysis. Ginger essential oil with α-zingiberene (24.9 ± 0.8%), β-sesquiphelladrene (11.7 ± 0.3%), ar-curcumene (10.7 ± 0.2%), and β-bisabolene (10.5 ± 0.3%) as the main compounds significantly inhibited the seed germination of P. oleracea, L. multiflorum, and C. selloana at the highest dose (1 µL/mL) assayed, as well as the hypocotyl and radicle growth of the weeds. Turmeric essential oil with ar-turmerone (38.7 ± 0.8%), β-turmerone (18.6 ± 0.6%), and α-turmerone (14.2 ± 0.9%) as principal components significantly inhibited the seed germination of C. selloana and hypocotyl and radicle growth of weeds (the latter in particular) at the highest dose, whereas it did not affect either the seed germination or seedling growth of the food crops. Turmeric essential oil can be an effective post-emergent bioherbicide against the tested weeds without phytotoxicity to crops.