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

Gray mold, caused by the fungus <i>Botrytis cinerea</i>, 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 <i>B. cinerea</i> in vitro, and its impact on plant physiological health and gray mold suppression in planta. EONE-treated media significantly reduced <i>B. cinerea</i> 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 <i>B. cinerea</i>. 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 <i>B. cinerea</i>-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 <i>B. cinerea</i>, with potential for a long-term protective effect in disease management.