Attivita' biocida di oli essenziali nei confronti del nematode galligeno Meloidogyne incognita

Root-knot nematodes, Meloidogyne species, are strongly destructive and extremely difficult to control due to their poliphagy and worldwide spread. The need of a higher sustainability of agricultural products is imposing the replacement of chemical nematicides with environmentally safer formulates. Formulates based on the nematicidal secundary metabolites present in many plant species may represent a concrete alternative to chemicals. In particular, plant essential oils and their constituents have a great potential of application for nematode control, either as nematicides themselves or as model compounds for the development of more active derivatives. Soil drench treatments with 0.05, 0.1 and 0.2 mg kg-1 soil solutions of different essential oils were comparatively tested against the root-knot nematode Meloidogyne incognita on tomato in two pot experiments. Essential oils from five different species, i.e. Schinus molle, Cinnamomum camphora, Eugenia caryophillata, Cinnamomum zeylanicum and Citrus aurantium were tested in the first experiment, whereas oils from two species of Eucalyptus spp., i.e. E. citriodora and E. globulosus, were applied in the second trial. Plant growth parameters, gall infestation and nematode multiplication on tomato roots were evaluated after a two-month permanence of plants in a greenhouse at 25 °C. In the first experiment, all the treatments with the five essential oils, but 0.05 and 0.1 mg kg-1 soil rates of C. zeylanicum, significantly suppressed the number of eggs and juveniles of M. incognita on tomato roots compared to the nontreated control. Effect of treatments was less evident on gall formation on tomato roots. Essential oils of S. molle and E. caryophillata were overall more effective than the other three oils. Tomato top and root biomass was not affected by all the tested treatments. In the second trial, all treatments with both Eucalyptus species significantly reduced gall formation and number of nematode eggs and juveniles on tomato roots and nematode reproduction rate compared to the nontreated control. The essential oil of E. citriodora showed a nematicidal activity globally higher than that of E. globulosus. Most treatments with both essential oils resulted also in a larger plant root system compared to the nontreated control, but did not affect plant top biomass. Soil treatments with essential oils formulations were confirmed to be an effective tool for a sustainable management of root-knot nematode infestations. Key words: root-knot nematodes, sustainable control, essential oils.