Profiling the Variability of Eucalyptus Essential Oils with Activity against the Phylum Nematoda

The genus Eucalyptus (Myrtaceae) comprises more than 800 species, mostly native to Australia. Eucalyptus essential oils (EOs) are well-known for their extremely high qualitative and quantitative variation in foliar terpenes (mainly mono- and sesquiterpenes). These EOs have a wide range of uses, from scientific applications, such as the taxonomic characterization of populations based on the chemical profiling of EO chemotypes, to industrial applications, including pharmaceutical, agrochemical, food and fragrances. In this study, we review the available information concerning the chemical variability of EOs from Eucalyptus spp. assayed against nematodes. The most active EOs belonged to E. globulus, E. staigeriana, and E. citriodora. Their chemical composition was mainly dominated by 1,8-cineole, limonene, p-cymene and citronellal in varying proportions. Nematicidal activity of Eucalyptus spp. EOs was reported against animal parasitic nematodes, including gastrointestinal nematodes (e.g., Haemonchus contortus), plant parasitic nematodes, such as root-knot nematodes (e.g., Meloidogyne incognita and M. chitwoodi) or the pinewood nematode Bursapelenchus xylophilus, and the free-living nematode Caenorhabditis elegans. Correlation between EO qualitative and quantitative composition with its respective activity may provide valuable information on the nematicidal specificity of EOs. This knowledge can be useful for devising environmentally safer pest management techniques for the conservation of ecosystems biodiversity.