Herbicidal activity of medicinal plants essential oil using nanotechnology for saffron weed control saffron weed control using medicinal plants’ essential oil

Weeds present a significant challenge to agricultural systems, particularly in the cultivation of high-value crops like saffron. In this study, allelopathic effects of ten medicinal and aromatic plants were screened on germination and growth of lettuce seedlings using the dishpack and cotton-swab methods. The results indicated that clove, ajwain, perovskia and cinnamon strongly inhibited the hypocotyl and radicle growth of lettuce. Then, essential oils (EOs) from the selected plants were formulated into nanoemulsions (in different HLB) and their properties (particle sizes and PDI) were evaluated. The nanoemulsion formulated herbicidal activity from Trachyspermum ammi (ajwain), Syzygium aromaticum (clove), Cinnamomum cassia (cinnamon), and Perovskia abrotanoides (Perovskia) EOs evaluated against common weeds (Agropyron repens, Bromus japonicus, Chenopodium album, Festuca spp). Nanoemulsion formulations with 1% essential oils and an HLB of 15 showed the smallest particle sizes, lower PDI, and greater stability at 4 °C. The results showed that nanoemulsion spraying induced morphological, physiological, and biochemical changes in the weeds. The application of clove, ajwain, perovskia and cinnamon EOs on Agropyron repens and Bromus sp. increased ion leakage. Cinnamon oil on Agropyron repens reduced chlorophyll index, SOD activity (40.7% ), and protein levels (79.83% ), while ajwain oil decreased catalase enzyme activity (39.56%). On Bromus, ajwain EOs caused the greatest reduction in chlorophyll index, while cinnamon and perovskia EOs reduced catalase activity (82.8% and 52.32%, respectively), and clove EO led to the most significant decrease in SOD activity (24%). Nanoemulsion spraying on Festuca caused increased ion leakage (93%) and reduced catalase enzyme activity with ajwain and cinnamon oils (74.87% and 63.07%, respectively), while clove and perovskia oils decreased SOD activity (45% and 41%, respectively). The application of 1% nanoemulsion solutions of natural essential oils caused visible leaf burn symptoms—such as yellowing, chlorosis, necrosis, and tip burn—in all tested weed species within the first five days, with cinnamon and ajwain oils leading to over 90% desiccation after seven days. The results suggest that essential oils, particularly cinnamon, ajwain and clove, could be effective natural herbicides with potential for use in sustainable weed management.