Development of bio‐nano‐herbicide using Eucalyptus citriodora essential oil against a notorious weed Echinochloa crus‐galli

Abstract BACKGROUND Weeds are a menace in agriculture causing crop yield reductions to the tune of 40–50%. To overcome the problems of weeds, herbicides have been used excessively to the extent that they have caused resistance in weeds, in addition to the environmental hazards. Nano‐herbicides are intended to exploit botanicals to develop novel bio‐nano‐herbicide formulations. Bio‐nano herbicide was developed using Eucalyptus citriodora essential oil combined high‐energy approaches such as ultra‐sonication and high‐pressure homogenization. The formulation has hydrodynamic and physical sizes of 95.5 and 32.3–57.7 nm, respectively. The product was tested for their pre‐emergence and post‐emergence herbicidal activity against Echinochloa crus‐galli. RESULTS Increased concentration of bio‐nano‐herbicide inhibited the pre‐emergence of weed seeds. Treated weed seeds registered lower dehydrogenase (0.80 to 0.32), alpha‐amylase (1.349 to 0.101 mg maltose), catalase (3.87 to 3.52 μmol H₂O₂ min −1 g −1 protein), peroxidase (3.96 to 3.61 U mg −1 protein min −1 ) and super oxide dismutase (0.94 to 0.56 U mg −1 protein min −1 ) activities than control. Further, foliar spray of 1% nanoemulsion recorded significantly lower total chlorophyll content (1.62 mg g −1 fresh weight), than the crude oil (2.58 mg g −1 ). The antioxidant enzyme activities increased immediately after the first spray and the weeds wilted after the second spray. CONCLUSION This study is a maiden attempt to clearly demonstrate that bio‐nano‐herbicide can be developed using Eucalyptus citriodora essential oil which has both pre‐emergence and post‐emergence inhibitory activities against the notorious weed Echinochloa crus‐galli . Field studies are to be taken up in the near future to validate the herbicidal efficacy of the novel nano herbicide formulation. © 2025 Society of Chemical Industry.