Use of Cinnamon Essential Oil Nanoemulsions to Manage Gray Mold in Tomato.

Gray mold, caused by the fungus Botrytis cinerea, significantly reduces tomato yield and quality. The use of essential oils (EOs), here formulated as nanoemulsions, offers a safe and eco-friendly strategy to manage gray mold without conventional pesticide application. This study evaluated the antifungal effect of cinnamon essential oil nanoemulsion (EONE) against B. cinerea in vitro, and its impact on plant physiological health and gray mold suppression in planta. EONE-treated media significantly reduced B. cinerea mycelial growth area compared to non-treated controls, with greatest inhibition observed at three days post-inoculation (PDA: 88.67%, p<0.01; V8: 54.57%, p<0.01). In tomato plants, roots were treated with EONE prior to foliar inoculation with B. cinerea. EONE showed no adverse effects on physiological parameters of non-inoculated plants. Inoculated plants exhibited reduced Fv/Fm, chlorophyll content, and NDVI compared to non-inoculated plants, but these effects were mitigated in EONE-treated plants, particularly at 200 µL application volume. Cinnamon EONE, applied at volumes ranging from 200 to 2000 µL (5.98 to 59.38 mg/L cinnamon EO), suppressed gray mold lesion area by up to 44.50% compared to the B. cinerea-inoculated control. Evaluation of individual EONE components showed that inert ingredients had no significant plant-protective nor disease-suppressive effects. While unformulated EO was more effective in suppressing disease lesion area in the short term (plants inoculated 24 h post-treatment), EONE provided longer-lasting protection when inoculated five days post-treatment. These findings suggest that cinnamon EONE is a promising tool for managing B. cinerea, with potential for a long-term protective effect in disease management.