Essential Oils in the Alternative Control of Postharvest Diseases in Strawberries: Anthracnose and Gray Mold

Strawberry (Fragaria × ananassa) is one of the most perishable fruits, requiring care from harvest to consumer arrival. Gray mold and anthracnose are the diseases that most affect this crop in the postharvest period. Essential oils have bioactive compounds that may help maintain fruit quality and retard fruit decay. This study aimed to evaluate the essential oils of Cymbopogon citratus (DC.) Stapf, Rosmarinus officinalis L., Cymbopogon winterianus Jowitt., Melaleuca alternifolia (Maiden & Betche) Cheel, and Cinnamonum camphora var. linaloolifera in the control of postharvest phytopathogens Botrytis cinerea and Colletotrichum acutatum in in vitro and in vivo assays. The essential oils were extracted by steam distillation and chemically analyzed (GC-MS). The antioxidant activity of the oils was evaluated by inhibiting DPPH^• and ABTS^•+ radicals. The in vitro treatments were zero and polysorbate 0.20% v/v, 0.01%, 0.05%, 0.10%, 0.15, and 0.20% v/v of each essential oil, diluted in polysorbate 20 (1:1), using the PDA culture medium. The evaluations were performed by measuring the average diameter of the colonies at 3, 5, 7, 10, and 14 days. For the in vivo test, the treatments were sprayed on the fruits; the two best concentrations of the in vitro test were mixed with water and the surfactant polysorbate 20 (1:1). After incubation, disease severity was assessed visually using a diagrammatic scale. Firmness, pulp pH, soluble solid content, and titratable acidity were also assessed. The essential oils tested in this study demonstrated fungicidal effects on both phytopathogens, whose concentrations varied between 0.05% and 0.20% v/v. Regarding the antioxidant and antifungal effects, the essential oils of C. citratus and C. winterianus had the highest antioxidant capacity and the strongest antifungal effect, suggesting a potential link between these biological effects. The essential oil of C. citratus showed, at a concentration of 0.05% v/v, total control of the development of B. cinerea and C. acutatum. It also demonstrated better soluble solid content and titratable acidity, resulting in better fruit flavor, thus providing better productivity and quality of strawberry fruits.