Abstract
Natural pesticides are in the forefront of interest as ecofriendly alternatives to their synthetic ancestors. In the present study, we evaluated the nematicidal activity of seven Greek Lamiaceae species and discerned among principal components for activity according to GC-MS analysis. Care was taken that all botanicals used were easily prepared without employing elaborate procedures and toxic solvents. We established the in vitro EC50 values of the hydrosols of Origanum vulgare L., Mentha piperita L., and Melissa officinalis L. and the water extracts of Origanum vulgare, Τhymus vulgaris L., Thymus citriodorus (Schreb), Rosmarinus officinalis (Spenn), and Ocimum basilicum L. against Meloidogyne javanica (Treub) and Meloidogyne incognita (Kofoid & White). Furthermore, we amended nematode-infested soil with powdered leaves and flowers of O. vulgare to assess for efficacy. According to in vitro studies, the most active botanical preparations against both nematode species was O. vulgare, as regards its hydrosol and water extract. Thymus citriodorus was proved very potent against M. javanica, provoking 100% paralysis at 4 μL/mL after 96 h, but was only nematostatic against M. incognita since the second-stage juveniles (J2s) recovered movement 48 h after immersion in test solutions. Interestingly, O. vulgare was also proved nematicidal in pot bioassays but at test concentrations over 50 g/kg was phytotoxic for tomato plants. According to GC-MS analysis, the principal components sustaining activity of O. vulgare are carvacrol and thymol. The nematicidal activity of O. vulgare seems promising in the forms of essential oil leftovers (i.e., hydrosol), self-prepared water extract that can be of consideration as α “basic substance”, and powder for soil amendment.
Highlights
Nematodes are among the most complex and numerous organisms on the planet
We have previously shown that the essential oils (EOs) of the family Lamiaceae, including the species Mentha pulegium L., Origanum vulgare, Origanum dictamnus L. and Melissa officinalis display powerful in vitro nematicidal activity [13]
The aromatic materials tested for the nematicidal activity against M. javanica and M. incognita include: (a) hydrosols obtained as aquatic leftovers after EO obtainment from Clevenger distillation of Origanum vulgare, Mentha piperita, and Melissa officinalis from the Aitheria Company based in Velvento, Kozani, Greece, and (b) water extracts from powdered plant parts of Origanum vulgare, Thymus vulgaris, Thymus citriodorus, Rosmarinus officinalis, and Ocimum basilicum obtained from the Ethericon Greek
Summary
Nematelminthes, is derived from the Greek word “νήμα” (thread or threadworms). They belong to the kingdom Animalia, phylum Nematoda [1]; and after arthropods, they form the second most numerous group of Metazoa. They have the form of a worm, with a cylindrical, elongated body and a circular cross-section. Root-knot nematodes (Meloidogyne sp.) cause considerable damage to more than 5000 plant species and use their stylets to feed on the roots of the plants. Meloidogyne incognita, M. javanica, and M. arenaria infect Solanaceae and Malvaceae, have broad host ranges, and are in the list of the most economically damaging root-knot nematodes [4]
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