Herbicidal potential of Brassica spp. essential oil: phytotoxicity and environmental impact

Brassica spp. (mustard) essential oils (EOs), rich in bioactive isothiocyanates, offer significant potential as natural herbicides for effective weed management. In this study, emulsions and nanoemulsions (NEms) of B. juncea I, B. nigra and B. juncea II EOs were formulated and evaluated for phytotoxic effects against major weeds associated with Triticum aestivum and Oryza sativa. EO emulsions exhibited concentration-dependent phytotoxicity, resulting in complete germination inhibition at 1.0% to 2.0%, 1.5% to 3.0% and 2.0% to 3.5% for B. juncea I, B. nigra and B. juncea II EOs, respectively, depending on the target species. The corresponding LC₅₀ values ranged from 0.134% to 0.750%, 0.186% to 1.1801% and 0.460% to 3.626% for B. juncea I, B. nigra and B. juncea II EO, respectively, indicating the highest phytotoxic potency of B. juncea I EO across the tested weed species. Compared with conventional emulsions, NEm formulations achieved equivalent phytotoxic effects at substantially lower concentrations, demonstrating improved herbicidal efficacy. Although both formulations were nonselective, adverse effects on crop germination were mitigated through charcoal coating (3 g/15 g of seeds) and pre-plant application (4-8 days before planting). The short half-life (1.88-4.55 days) and transient dehydrogenase inhibition ensured effective weed control with minimal environmental impact-NEms of Brassica spp. EOs represent a promising eco-friendly strategy for sustainable weed management.