The potential of essential oils from medicinal plants as "new age pesticides" in agriculture

Aromatic plants naturally produce essential oils (EOs) as secondary metabolites in the secretory glands of specific plant organs. These oils provide both direct and indirect defenses against herbivores and pathogenic microorganisms. EOs are composed of complex mixtures of terpenes, terpenoids, and phenylpropanoids as their primary components. Known for their antioxidant, antimicrobial, and anti-inflammatory properties, EOs derived from medicinal plants have broad applications in cosmetics, the food industry, and traditional medicine. By the end of the twentieth century, the antimicrobial properties of EOs had attracted significant scientific interest, highlighting their potential as alternatives to synthetic pesticides in agriculture. Among the most studied and widely used EOs for their bioactive effects on plant pathogens, pests, and weeds are those derived from citronella, lavender, rosemary, lemongrass, thyme, peppermint, cinnamon, clove, eucalyptus, sage, tea tree, oregano, and citrus. Although the literature contains extensive data on the effectiveness of EOs against plant pathogens, pests, and weeds, their practical application in agriculture remains surprisingly limited. The main limitations for their commercial use in agriculture include manufacturing constraints, their lipophilic and highly volatile nature, production costs, and variability in their composition. Emerging innovations, such as nanoencapsulation, offer promising solutions to overcome some of these challenges. This review compiles and discusses the latest scientific literature on the biological activities of EOs from medicinal plants against plant pathogens, pests, and weeds, their chemical composition, and modes of action. Additionally, thereview explains both the benefits and limitations of using EOs as alternatives to synthetic pesticides, as well as the regulatory and approval processes involved.
Keywords: biopesticides, terpens, terpenoides, phenylpropanoids, mode of action, regulations, agriculture