Phytotoxic effects and environmental safety of nanoparticles incorporating a eucalyptus essential oil.

Eucalyptus essential oils (EOs) have strong herbicidal properties, making them promising alternatives to synthetic pesticides. However, their high volatility and hydrophobicity can limit their application. Thus, this study aimed to incorporate a Eucalyptus globulus Labill. EO into nanoparticles and evaluate their herbicidal potential and environmental safety. Briefly, a commercial eucalyptus essential oil (CEEO) was incorporated into lipid (LN-CEEO) and keratin (KN-CEEO) nanoparticles. Both nanoformulations exhibited high encapsulation efficiencies (approximately 99%), adequate long-term stability, and distinct release profiles, with LN-CEEO providing more sustained CEEO release and KN-CEEO releasing the oil faster. Their herbicidal activity was tested by foliar-spraying purslane (Portulaca oleracea L.) seedlings with CEEO, LN-CEEO, and KN-CEEO at 50, 75, and 100% (v/v). Bulk CEEO at 100% induced 98% weed mortality, whereas LN-CEEO induced only 10% mortality and KN-CEEO showed no herbicidal effects. To assess their environmental safety on non-target plants, tomato (Solanum lycopersicum L.) seedlings were cultivated in soils where weeds had been previously treated with these formulations. Plants grown in soils contaminated with KN-CEEO exhibited reduced growth and strong redox imbalances in shoots and roots. In contrast, CEEO and LN-CEEO stimulated the antioxidant system without compromising plant growth, with LN-CEEO even promoting root elongation. Overall, this study provides, for the first time, insights into the development of EO-based nanoparticles for weed management and highlights the need to optimize their herbicidal performance while ensuring environmental safety.