Chemical Composition and Nematicidal Properties of Sixteen Essential Oils-A Review

Essential oils (EOs) can be a large source of new food-safe and healthy nematicidal products,due to their strong activity on crop pathogens and pests, including phytoparasitic nematodes, aswell as to their low environmental persistence. This review summarizes the results from our 10-yearstudies on chemical features and nematicidal properties of 16 EOs with different botanical originsand compositions, i.e., the EOs from Artemisia herba-alba Asso (Asteraceae), Cinnamomum camphora(L.) J. Presl. and Cinnamomum verum J. Presl. (Lauraceae), Citrus aurantium L., Cinnamomum. sinensis L.Osbeck and Ruta graveolens L. (Rutaceae), Eucalyptus citriodora Hook, Eucalyptus globulus Labill. andSyzygium aromaticum (L.) Marry et Perry (Myrtaceae), Mentha piperita L., Monarda didyma L., Monarda.fistulosa L., Rosmarinus officinalis L. and Thymus satureioides Cosson (Lamiaceae), Pelargonium asperumEhrh ex Willd (Geraniaceae) and Schinus molle L. (Anacardiaceae). All these EOs were chemicallycharacterized and tested in vitro and/or in vivo for their activity against the phytoparasitic speciesMeloidogyne incognita Kofoid et White (Chitw.), Pratylenchus vulnus Allen et Jensen and Xiphinemaindex Thorne et Allen. Toxicity bioassays were conducted by exposing 2nd stage juveniles (J2) ofM. incognita, mixed-age specimens of P. vulnus and adult females of X. index to 2-100 µg mL-1concentrations of EOs or EO's major constituents for 4-96 h and checking mortality effect after afurther 24-72 h permanence in water. Egg hatchability bioassays consisted in exposing (24-48 h)M. incognita egg masses to 500-1000 mg mL-1 EO solutions followed by a 5-week hatching test inwater. The in vivo experiments were undertaken in sandy soil strongly infested by M. incognita andtreated with different doses of EOs, applied either in water solution or by fumigation. The effectsof the treatments on nematode infestation on tomato and in soil were checked at the end of eachexperiment. Structure-activity relationships, as suggested by the different chemical compositions oftested EOs, were also highlighted. In agreement with literature data, our studies indicated that mostof the tested EOs are highly suitable for the formulation of new safe nematicides, though still retardedby the lack of efficient stabilization processes and standardized EOs' components and extractiontechniques.