Essential Oils in Plant Protection in Europe: A Review of Efficacy and Limitations of Use

Essential oils are increasingly investigated for their potential use in plant protection because of their insecticidal, fumigant, repellent, behavioural, and antifungal activities. This narrative review with a structured literature search synthesizes evidence relevant to European plant protection, focusing primarily on stored-product pests, with additional consideration of pests and plant pathogens outside storage systems, stage-specific susceptibility, formulation, practical limitations, and the EU regulatory framework. EO efficacy was strongly influenced by chemical composition, concentration, formulation, exposure time, developmental stage, target species, and environmental conditions. The strongest evidence was identified for stored-product pests (Coleoptera), although stage-specific susceptibility varied among species. Under field conditions, the practical application of essential oils remains challenging due to their high volatility, short persistence, sensitivity to environmental conditions, potential phytotoxicity, formulation requirements, and limited field validation. Methodological differences among assay types also limit direct comparison across studies. In the EU, regulatory acceptance remains substance-specific, with whole essential oils assessed separately from their individual volatile constituents. Most available evidence is derived from laboratory studies, while greenhouse and field validation remains limited. No formal methodological quality or risk-of-bias assessment of individual studies was performed. Overall, essential oils should be regarded as complementary, application-specific tools whose contribution to more sustainable plant protection depends on improved standardization, formulation, field validation, safety, economic viability, and regulatory acceptance.