Relationship between chemical composition and nematicidal activity of different essential oils

In this study, the relationship between nematicidal activity and chemical composition of ten essential oils (EOs) from different plant species was investigated both in in vitro assays on juveniles (J2) and eggs of the root-knot nematode Meloidogyne incognita and in experiments on tomato in soil infested by M. incognita. Nematode J2 were exposed for 4, 8 or 24 h to 0.78–100 µg mL−1 concentrations of each EO, whereas 24, 48 or 96 h exposures to 250, 500 and 1000 µg mL−1 solutions were tested on M. incognita egg masses. Treatments with 50, 100 or 200 µg kg soil rates of each EO were applied in the experiment on potted tomato. The highest nematicidal potential resulted for the C. verum EO, as highly toxic to both M. incognita J2 and eggs and strongly suppressive on nematode multiplication on tomato roots. The infestation of M. incognita on tomato roots was also strongly reduced by the EOs from E. citriodora and S. aromaticum, both highly toxic to M. incognita J2 but less active on nematode eggs. Adversely, R. graveolens EO strongly inhibited the egg hatch but was limitedly toxic to the infective J2. Chemical composition of the EOs was determined by GC-FID and GC-MS. The ten EOs showed a very different chemical composition in terms of major phytochemicals, with one or two dominant components totally amounting up to 85%. The structure–activity relationship based on the main phytochemicals identified in the assayed EOs and their nematicidal effects on M. incognita was also discussed. Results from this study confirmed that the selection of suitable EO raw materials can lead to the formulation on new effective nematicidal products

Side effects of biostimulants against root-knot nematodes on tomato

Plant biostimulants are often reported for their suppressive side effects against root-knot nematodes, due to an enhancement of host-plant resistance or to direct nematoxicity. Effects of soil treatments with four different commercial biostimulants based on quillay extract, sesame oil, neem seed cake or algae were investigated against the root-knot nematode Meloidogyne incognita on tomato in potting mixes. Infested soil, either untreated or treated with Oxamyl, and uninfested soil were used as controls. Numbers of nematode eggs and juveniles and gall formation on tomato roots and plant fresh top and root weight were checked at 75 days after transplanting. Treatments with neem cake, sesame oil and quillay extract formulations resulted in a significant reduction of nematode multiplication and gall formation on tomato roots compared with untreated controls, and were not significantly different from treatment with Oxamyl. Neem cake and sesame oil were also significantly more suppressive than the quillay extract formulation in the first experiment. The algae formulation provided the lowest effect on nematode infestation, causing only a slight significant reduction of eggs and galls on tomato roots only in the first experiment. Almost all treatments with the four biostimulants also significantly increased tomato plant growth, though the best growth effect was always provided by the quillay formulation. Results from these experiments seem to indicate that biostimulants may play a role in sustainable nematode management strategies, either by limiting nematode impact on plant growth and/or by directly suppressing multiplication

Potential of soil biofumigation with essential oils for the control of root-knot nematodes on tomato

Effectiveness of soil fumigation with 50, 100 and 200 L kg-1 soil of essential oils of Eucalyptus citriodora, Eucalyptus globulus, Mentha pulegium, Pelargonium asperum and Ruta graveolens was assessed against the root-knot nematode Meloidogyne incognita on potted tomato. Plant growth parameters and number of galls and nematode eggs and juveniles on tomato roots were evaluated after a two-month permanence of plants at 25 °C in greenhouse. Essential oils of E. globulus and P. asperum significantly reduced nematode multiplication and gall formation on tomato roots at all the tested rates, whereas those of E. citriodora, M. pulegium and R. graveolens were suppressive only at more than 50 L kg-1 soil. Oils of P. asperum and E. globulus also resulted in the largest increase of plant top and root biomass

Biostimulants for Plant Growth Promotion and Sustainable Management of Phytoparasitic Nematodes in Vegetable Crops

The parasitism of root-knot nematodes, Meloidogyne spp., can cause heavy yield losses to vegetable crops. Plant biostimulants are often reported for a side-suppressive eect on these pests and many commercial products are increasingly included in sustainable nematode control strategies. Source materials of most biostimulants derived from plant or seaweed raw materials were documented for a reliable suppression of root-knot nematode species, whereas the suppressiveness of microbial biostimulants was found largely variable, as related to the crop and to environmental factors. Chitosan-based biostimulants were also stated for a variable phytonematode suppression, though clearly demonstrated only by a few number of studies. In a preliminary experimental case study, four commercial biostimulants based on quillay extract (QE), sesame oil (SO), seaweeds (SE), or neem seed cake (NC) were comparatively investigated for their eects against the root-knot nematode M. incognita on potted tomato. Soil treatments with all the four biostimulants resulted in a significant reduction of nematode eggs and galls on tomato roots, though NC and SO were significantly more suppressive than QE or SE. In addition, almost all biostimulant treatments also resulted in a significant improvement of tomato growth compared to the non-treated control. These preliminary results seem to confirm the literature data and clearly indicate the potential role of biostimulants for a safe nematode management both in organic and integrated crop systems

Plant metabolites for management of plant parasitic nematodes

lant-parasitic nematodes are among the best known crop pests responsible for substantial value loss of crops of agronomic importance. Management of these pests has been mainly achieved with chemical nematicides throughout the past decades. Overuse of synthetic pesticides has generated a series of environmental problems and human and animal health concerns leading to their progressive withdrawal from the European market as well as to consider the use of alternative control strategies. In the recent years the interest in the application of botanical nematicides has increased tremendously, leading to the discover of new plant sources, plant extracts and phytochemicals with potential as nematicidals. Groups of plant secondary metabolites most promising in the development of pesticidal formulations are glucosinolates,saponins and terpenoid phytoconstituents. In the present communication we will describe our latest results on the nematicidal effects of selected plant extracts rich in the above mentioned compounds as well as the biocidal activity of pure plant metabolites against highly destructive phytoparasites such as the root-knot nematode Meloidogyne incognita or the ectoparasite dagger nematode Xiphinema index

Plant metabolites for management of plant parasitic nematodes

lant-parasitic nematodes are among the best known crop pests responsible for substantial value loss of crops of agronomic importance. Management of these pests has been mainly achieved with chemical nematicides throughout the past decades. Overuse of synthetic pesticides has generated a series of environmental problems and human and animal health concerns leading to their progressive withdrawal from the European market as well as to consider the use of alternative control strategies. In the recent years the interest in the application of botanical nematicides has increased tremendously, leading to the discover of new plant sources, plant extracts and phytochemicals with potential as nematicidals. Groups of plant secondary metabolites most promising in the development of pesticidal formulations are glucosinolates,saponins and terpenoid phytoconstituents. In the present communication we will describe our latest results on the nematicidal effects of selected plant extracts rich in the above mentioned compounds as well as the biocidal activity of pure plant metabolites against highly destructive phytoparasites such as the root-knot nematode Meloidogyne incognita or the ectoparasite dagger nematode Xiphinema index

Biocide plants as a sustainable tool for the control of pests and pathogens in vegetable cropping systems

Synthetic pesticides have played a major role in crop protection related to the intensification of agricultural systems. In the recent years, environmental side effects and health concerns raised by an indiscriminate use have led the EU to the ban of many synthetic pesticides. As a result of this drastic revision, currently there is a strong need for new and alternative pest control methods. An interesting source of biorational pesticides may be represented by the biocidal compounds naturally occurring in plants as products of the secondary metabolism. Groups of plant secondary metabolites most promising for the development of pesticidal formulations are glucosinolates, saponins, and more generally terpenoid phytoconstituents, such as essential oil and their constituents. Glucosinolates are thioglucosidic secondary metabolites occurring mainly in the Brassicaceae and, at a less extent, in Capparidaceae families. The incorporation of glucosinolate- containing plant material into the soil results in degradation products highly toxic to soilborne pest, pathogens and weeds. This practice, known as biofumigation, may be considered as an ecological alternative to soil toxic fumigants. Plant-derived saponins are triterpene glycosides present in top and root tissues of plant species of the families Leguminosae, Alliaceae, Asteraceae, Polygalaceae and Agavaceae. Saponins and saponin-rich plant materials have been also reported for a biocidal activity on phytoparasites and soilborne plant pathogens. Essential oils are volatile, natural, heterogeneous mixtures of single substances, mainly terpenes and phenolics, formed as secondary metabolites by aromatic plants belonging to several botanical families. Among terpenes, limonoid triterpenes have been demonstrated to possess interesting insecticidal, nematicidal and antifungal properties. Occurrence of these compounds is mainly limited to Meliaceae and Rutaceae. Alkaloids, phenolics, cyanogenic glucosides, polyacetylenes and polythienyls are further groups of secondary metabolites also known for their biocidal activity and susceptible for the production of natural pesticides. Alkaloids are derived from various botanical families, amongst which the Solacaneae, and include a number of molecules, such as nicotine, veratrine, cevatrine and ryanodine, used as insecticides. Phenolics were found also toxic to insects, fungi, bacteria, nematodes and weeds. Cyanogenic glucosides are amino acidderived secondary metabolites releasing, upon tissue disruption, hydrogen cyanide that suppress insects, fungus, nematodes and weeds. Finally, polyacetylenes and polythienyls, substances mainly present in Tagetes species, are also well known for their insecticidal and nematicidal properties