Plant essential oils against woody plant fungal pathogens: chemical composition, antifungal mechanisms, and translational challenges

Woody plants are threatened by fungal and oomycete pathogens that cause root and wood rots, cankers, vascular wilts, dieback, fruit decay, and other diseases. Meanwhile, intensive production systems and repeated fungicide use have raised concerns about resistance, environmental persistence, and non-target effects. Essential oils (EOs) have emerged as promising natural antimicrobial resources, yet their effectiveness depends strongly on chemical composition, pathogen susceptibility, concentration, formulation, and application strategy. This review synthesizes current evidence on EO-based management of pathogens affecting forest trees, fruit trees, woody crops, and wood materials, emphasizing the chemical and biological determinants of antifungal efficacy. Across diverse pathosystems, EO activity is associated with phenolic monoterpenes, aldehydes, monoterpene hydrocarbons, and oxygenated terpenoids, while chemotypic and geographical variation can substantially influence performance. EOs act through multiple complementary mechanisms, including disruption of fungal cell membranes and walls, ergosterol depletion, interference with sterol and cell-wall biosynthesis, mitochondrial dysfunction, oxidative stress, morphological damage, inhibition of spore germination, and suppression of pathogen development. Some EOs may additionally stimulate host defense responses, indicating that disease suppression can involve both direct antifungal activity and plant-mediated resistance. Advances in vapor delivery, coatings, nanoemulsions, and wood-preservative applications further enhance their potential. However, practical deployment remains limited by compositional variability, volatility, phytotoxicity, formulation instability, limited persistence, inconsistent dose responses, and insufficient field validation. Future research should prioritize standardization, mechanism-guided formulation, synergistic combinations, ecotoxicological assessment, techno-economic evaluation, and field- and commercial-scale validation to enable reliable integration of EOs into sustainable woody plant disease management.