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Nematodes have a negative impact on crop production and yield. The use of synthetic formulations to control plant parasitic nematodes carries both environmental and human health risks. As these agrochemicals are gradually being phased out, recent research has been focused on finding more environmentally friendly, plant-based alternatives. This study aims to investigate the effectiveness of botanicals, used alone or in artificial blends, in paralyzing Meloidogyne incognita second-stage juveniles (J2s) immersed in test solutions or exposed to vapors. We tested thymol, trans-anethole, and two lavender essential oils, referred to as LEOA and LEOB, which vary in their flower and stem compositions. We also employed in our study Melia azedarach aqueous extract (MWE), already proven to have considerable nematicidal activity. According to our findings, all treatments used individually exhibited considerable efficacy, even LEOA and LEOB first reported herein. In addition, all blends exhibited significant synergism, and the best-performing were trans-anethole/thymol, being synergic to paralyzing J2s for up to two days, and trans-anethole/LEOB as well as trans-anethole/MWE, provoking irreversible paralysis since the first day of J2 immersion in test solutions. Most importantly, the blend of trans-anethole with LEOA displayed the best effective synergism against M. incognita both for immersion and fumigation methods. Lastly, the chemical composition analysis displayed linalyl acetate and β-linalool as the major components of LEOA and β-linalool and eucalyptol as the major components of LEOB.

The Meloidogyne genus is widely recognized for its significant economic and scientific importance within the group of plant-parasitic nematodes. The chemical management of nematodes presents its challenges and heavily depends on employing soil fumigants containing toxic and costly nematicides. However, plant-derived essential oils offer promising alternatives, demonstrating a wide range of biological activities that affect nematodes through a range of mechanisms, including disrupting their nervous systems, inducing detrimental effects on plasma membrane permeability, penetrating the gelatinous matrix of nematode eggs, and disturbing intracellular redox status. Most of the extracted essential oils were predominantly sourced from the Lamiaceae family (32%), followed by Asteraceae (11%), Apiaceae (9%), and Poaceae (8%), and with genera Thymus, Mentha, Ocimum, Artemisia, Cymbopogon being the most common. The nematicidal activity of EOs primarily arises from their chemical groups, such as terpenes, phenylpropanoids, and organosulfur compounds. Among these, geraniol, carvacrol, limonene, eugenol, thymol, and pinene demonstrate the strongest nematicidal potential. The assessed EO efficacy was evaluated against 6 species belonging to the genus Meloidogyne. This review also provides knowledge of synergistic and antagonistic interactions of EO components. Synergistic interactions were identified between carvacrol and geraniol, as well as geraniol and eugenol, whereas binary combinations of carvacrol, γ-terpinene, and o-cymene exhibited reduced efficacy. Understanding how specific compounds interact can lead to the development of more potent and effective final products.

In a greenhouse experiment, we studied the impact of Melia azedarach ripe fruit water extract (MWE), Furfural (a key ingredient of M. azedarach), and the commercial nematicide Oxamyl (Vydate® 10 SL) on the soil free-living nematode community. Treatments were applied every 20 days for two months, and soil samples were collected 3 days after the last application (3DAA) and at the end of the cultivation period (34DAA). We assessed short- and long-term effects on nematode community structure, metabolic footprint, genus composition, and interaction networks. Oxamyl and Furfural significantly reduced bacterial and fungal feeder populations. MWE had no impact on free-living nematode populations. Oxamyl and Furfural-treated soil samples were dominated by Rhabditis at 3DAA and Meloidogyne spp. at 34DAA. On the contrary, MWE-treated soil showed a balanced distribution, with Rhabditis, Panagrolaimus, Mesorhabditis, and Diploscapter being equally abundant. MWE treatment exhibited higher diversity indices (Shannon and Simpson) and equitability. Network analysis showed that the Oxamyl network had the highest fragmentation, while the MWE and Furfural networks had higher cohesion compared to the control. Mesorhabditis spp. in the MWE network played a crucial role, being directly connected to the omnivore genera Thonus and Aporcelaimellus. Our results indicated that continuous MWE application, besides controlling Meloidogyne spp., could enhance the structure and stability of the soil-free-living nematode community.

Pesticides are substances that prevent, repel, suppress, mitigate, or eradicate harmful organisms [...]

To date, only a handful of pesticides have been authorized by the European Council for the protection of stored grains. Resistance issues and ecotoxicity concerns necessitate the development of ecofriendly tools in that direction. In this review, we refer to the recent findings on plant extracts and pure plant-derived substances with promising biological activity and the potential to be used as biopesticides for stored products. The main aim of biopesticides is to be effective against target pests, without harming humans and the environment. Many plant species, among those reported herein, are part of the human diet, and are thus not harmful to humans. Edible plant extracts produced with inorganic solvents represent safe candidates for use as repellants, fumigants or contact pesticides. Cinnamon, rosemary, parsley, garlic, oregano and basil are found in products destined for human consumption but also display significant biological activities. Interestingly, cinnamon is one of the most widely tested botanical matrixes, exhibiting the best lethal effects on almost all insect and mite taxa reported herein (Acaroidea, Coleoptera and Lepidoptera), followed by basil and garlic. Prunus persica,Azadirachta indica A. Juss and Carum sp. seem to be very promising too as miticides and/or insecticides, with A. indica already being represented commercially by a plant-derived acaricidal formulation.

In a greenhouse experiment, we studied the impact of Melia azedarach ripe fruit water extract (MWE), Furfural (a key ingredient of M. azedarach), and the commercial nematicide Oxamyl (Vydate® 10 SL) on the soil free-living nematode community. Treatments were applied every 20 days for two months, and soil samples were collected 3 days after the last application (3DAA) and at the end of the cultivation period (34DAA). We assessed short- and long-term effects on nematode community structure, metabolic footprint, genus composition, and interaction networks. Oxamyl and Furfural significantly reduced bacterial and fungal feeder populations. MWE had no impact on free-living nematode populations. Oxamyl and Furfural-treated soil samples were dominated by Rhabditis at 3DAA and Meloidogyne spp. at 34DAA. On the contrary, MWE-treated soil showed a balanced distribution, with Rhabditis, Panagrolaimus, Mesorhabditis, and Diploscapter being equally abundant. MWE treatment exhibited higher diversity indices (Shannon and Simpson) and equitability. Network analysis showed that the Oxamyl network had the highest fragmentation, while the MWE and Furfural networks had higher cohesion compared to the control. Mesorhabditis spp. in the MWE network played a crucial role, being directly connected to the omnivore genera Thonus and Aporcelaimellus. Our results indicated that continuous MWE application, besides controlling Meloidogyne spp., could enhance the structure and stability of the soil-free-living nematode community. [ABSTRACT FROM AUTHOR]

We investigated the effects of three botanicals with nematicidal properties (anise-Pimpinella anisum, parsley-Petroselinum crispum, and rocket-Eruca sativa) on the soil nematode community, in terms of trophic structure and nematode genera composition. We compared effects with those of fluopyram (synthetic nematicide) and Nemagold (bionematicide). We assessed the role of time, by sampling 15 and 45 days after treatments and analyzing nematode genera and microbial phospholipid fatty acid biomarkers (PLFA). Soil incorporation of botanicals reduced plant parasitic nematodes, increased bacterivores, especially the enrichment opportunists and among them Rhabditis, having no effect on fungivores and non-parasitic plant feeders. Neither the number nor the composition and dominance hierarchy of nematode genera were affected. Nemagold did not induce any significant change, while fluopyram decreased both free-living and parasitic nematodes, but with no uniform effect against all genera. The least affected genus was the fungivorous Aphelenchus. While most microbial PLFAs increased with time, the abundances of nematode genera did not change, except the Meloidogyne incognita second stage juveniles, which emerged in soil only 45 days after treatments. The low enrichment index and high channel index values of the fluopyram soil samples indicated a stressful environment. The opposite was observed in the botanical treatments, especially parsley and rocket.

Most insecticides commonly used in storage facilities are synthetic, an issue that generates concerns about food safety and public health. Therefore, the development of eco-friendly pest management tools is urgently needed. In the present study, a 6% (w/w) Hazomalania voyronii essential oil-based nanoemulsion (HvNE) was developed and evaluated for managing Tribolium confusum, T. castaneum, and Tenebrio molitor, as an eco-friendly wheat protectant. Larval and adult mortality was evaluated after 4, 8, and 16 h, and 1, 2, 3, 4, 5, 6, and 7 days, testing two HvNE concentrations (500 ppm and 1000 ppm). T. confusum and T. castaneum adults and T. molitor larvae were tolerant to both concentrations of the HvNE, reaching 13.0%, 18.7%, and 10.3% mortality, respectively, at 1000 ppm after 7 days of exposure. However, testing HvNE at 1000 ppm, the mortality of T. confusum and T. castaneum larvae and T. molitor adults 7 days post-exposure reached 92.1%, 97.4%, and 100.0%, respectively. Overall, the HvNE can be considered as an effective adulticide or larvicide, depending on the target species. Our results highlight the potential of H. voyronii essential oil for developing green nanoinsecticides to be used in real-world conditions against key stored-product pests.

Soil amendments with plant materials from Medicago species are widely acknowledged for a suppressive effect on plant-parasitic nematodes but their impact on beneficial components of soil nematofauna is still unknown. A study on potted tomato was carried out to investigate the short-time effects on the overall nematofauna of dry biomasses from six different Medicago species, i.e., M. sativa, M. heyniana, M. hybrida, M. lupulina, M. murex and M. truncatula, incorporated to natural soil at 10, 20, or 40 g kg−1 soil rates. All amendments resulted in a significant decrease of the total nematofauna biomass, whereas total abundance was significantly reduced only by M. heyniana, M. hybrida, and M. lupulina biomasses. Almost all the Medicago amendments significantly reduced the relative abundance of plant-parasites and root fungal feeders. All amendments significantly increased the abundance of bacterivores, whereas fungivores significantly increased only in soil amended with M. heyniana, M. lupulina and M. sativa plant materials. Mesorhabditis and Rhabditis were the most abundant genera of bacterivores, whereas Aphelenchoides and Aphelenchus prevailed among the fungivores. Predators were poorly influenced by all the tested Medicago biomasses, whereas the abundance of omnivores was negatively affected by M. heyniana and M. lupulina. Values of the Maturity Index and Sum Maturity Index were reduced by treatments with M. heyniana, M. hybrida, M. lupulina and M. sativa plant materials, whereas most of the tested amendments decreased values of the Channel Index while increasing those of the Enrichment Index. Enrichment and bacterivore footprints raised following soil addition with Medicago biomasses, whereas composite and fungivore footprints were significantly reduced. According to their overall positive effects on soil nematofauna, amendments with Medicago plant materials or their formulated derivatives could represent an additional tool for a sustainable management of plant-parasitic nematodes.

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.

The olive tree (Olea europaea L.) is an emblematic, long-living fruit tree species of profound economic and environmental importance. This study is a literature review of articles published during the last 10 years about the role of beneficial microbes [Arbuscular Mycorrhizal Fungi (AMF), Plant Growth Promoting Rhizobacteria (PGPR), Plant Growth Promoting Fungi (PGPF), and Endophytes] on olive tree plant growth and productivity, pathogen control, and alleviation from abiotic stress. The majority of the studies examined the AMF effect using mostly Rhizophagus irregularis and Glomus mosseae species. These AMF species stimulate the root growth improving the resistance of olive plants to environmental and transplantation stresses. Among the PGPR, the nitrogen-fixing bacteria Azospirillum sp. and potassium- and phosphorous-solubilizing Bacillus sp. species were studied extensively. These PGPR species were combined with proper cultural practices and improved considerably olive plant’s growth. The endophytic bacterial species Pseudomonas fluorescens and Bacillus sp., as well as the fungal species Trichoderma sp. were identified as the most effective biocontrol agents against olive tree diseases (e.g., Verticillium wilt, root rot, and anthracnose).

A total of 461 indigenous Streptomycetes strains recovered from various Greek rhizosphere habitats were tested for their bioactivity. All isolates were examined for their ability to suppress the growth of 12 specific target microorganisms. Twenty-six were found to exert antimicrobial activity and were screened for potential nematicidal action. S. monomycini ATHUBA 220, S. colombiensis ATHUBA 438, S. colombiensis ATHUBA 431, and S. youssoufensis ATHUBA 546 were proved to have a nematicidal effect and thus were further sequenced. Batch culture supernatants and solvent extracts were assessed for paralysis on Meloidogyne javanica and Meloidogyne incognita second-stage juveniles (J2). The solvent extracts of S. monomycini ATHUBA 220 and S. colombiensis ATHUBA 438 had the highest paralysis rates, so these Streptomycetes strains were further on tested for nematodes’ biological cycle arrest on two Arabidopsis thaliana plants; the wild type (Col-0) and the katanin mutant fra2, which is susceptible to M. incognita. Interestingly, S. monomycini ATHUBA 220 and S. colombiensis ATHUBA 438 were able to negatively affect the M. incognita biological cycle in Col-0 and fra2 respectively, and increased growth in Col-0 upon M. incognita infection. However, they were ineffective against M. javanica. Fra2 plants were also proved susceptible to M. javanica infestation, with a reduced growth upon treatments with the Streptomyces strains. The nematicidal action and the plant-growth modulating abilities of the selected Streptomycetes strains are discussed.

To date, there has been great demand for ecofriendly nematicides with beneficial properties to the nematode hosting plants. Great efforts are made towards the chemical characterization of botanical extracts exhibiting nematicidal activity against Meloidogyne spp., but only a small percentage of these data are actually used by the chemical industry in order to develop new formulates. On the other hand, the ready to use farmer produced water extracts based on edible plants could be a sustainable and economic solution for low income countries. Herein, we evaluate the nematicidal potential of Stevia rebaudiana grown in Greece against Meloidogyne incognita and Meloidogyne javanica, two most notorious phytoparasitic nematode species causing great losses in tomato cultivation worldwide. In an effort to recycle the plant’s remnants, after leaves selection for commercial use, we use both leaves and wooden stems to test for activity. In vitro tests demonstrate significant paralysis activity of both plant parts’ water extracts against the second-stage juvenile (J2) of the parasites; while, in vivo bioassays demonstrated the substantial efficacy of leaves’ powder (95% at 1 g kg−1) followed by stems. Interestingly, the incorporation of up to 50 g powder/kg of soil is not phytotoxic, which demonstrates the ability to elevate the applied concentration of the nematicidal stevia powder under high inoculum level. Last but not least, the chemical composition analyses using cutting edge analytical methodologies, demonstrated amongst components molecules of already proven nematicidal activity, was exemplified by several flavonoids and essential oil components. Interestingly, and to our knowledge, for the flavonoids, morin and robinin, the anthocyanidin, keracyanin, and a napthalen-2-ol derivative is their first report in Stevia species.

The intensification of agriculture has created concerns about soil degradation and toxicity of agricultural chemicals to non-target organisms. As a result, there is great urgency for discovering new ecofriendly tools for pest management and plant nutrition. Botanical matrices and their extracts and purified secondary metabolites have received much research interest, but time-consuming registration issues have slowed their adoption. In contrast, cultural practices such as use of plant matrices as soil amendments could be immediately used as plant protectants or organic fertilizers. Herein, we focus on some types of soil amendments of botanical origin and their utilization for nematicidal activity and enhancement of plant nutrition. The mode of action is discussed in terms of parasite control as well as plant growth stimulation.

In recent years, interest has surged in the development of plant extracts into botanical nematicides as ecofriendly plant protection products. Aromatic plants are maybe the most studied category of botanicals used in this direction and the yielding essential oils are obtained on a commodity scale by hydro distillation. Nevertheless, can the bioactivity of aromatic plants always be attributed to the terpenes content? What would it mean for soil microcosms to bear the treatment of an essential oil to cure against Meloidogyne sp.? Are there other extraction procedures to prepare more ecofriendly botanical products starting from an aromatic material? Lemon thyme is studied herein for the first time for its nematicidal potential. We compare the efficacy of lemon thyme powder, macerate, water extract and essential oil to control Meloidogyne incognita (Chitwood) and Meloidogyne javanica (Chitwood), and we additionally study the secondary effects on soil microbes and free-living nematodes, as well as on tomato plant growth. According to our results lemon thyme powder enhances tomato plants’ growth in a dose-response manner and when it is incorporated in soil at 1 g kg−1, it exhibits nematicidal activity at a 95% level on M. incognita. The water extract yielding from the same dose is nematicidal only if it is left unfiltered; otherwise only a paralysis effect is demonstrated but inside the soil the biological cycle of the pest is not arrested. The essential oil is good both in performing paralysis and biological cycle arrest, but it detrimentally lowers abundances of bacterial and fungal feeding nematodes. On the contrary, lemon thyme powder and unfiltered water extract augments the bacterial biomass, while the latter also increases the bacterivorous nematodes. Overall, the bio fertilizing lemon thyme powder and its unfiltered water extract successfully control root knot nematodes and are beneficial to soil microbes and saprophytic nematodes.

Meloidogyne incognita is a root knot nematode (RKN) species which is among the most notoriously unmanageable crop pests with a wide host range. It inhabits plants and induces unique feeding site structures within host roots, known as giant cells (GCs). The cell walls of the GCs undergo the process of both thickening and loosening to allow expansion and finally support nutrient uptake by the nematode. In this study, a comparative in situ analysis of cell wall polysaccharides in the GCs of wild-type Col-0 and the microtubule-defective fra2 katanin mutant, both infected with M. incognita has been carried out. The fra2 mutant had an increased infection rate. Moreover, fra2 roots exhibited a differential pectin and hemicellulose distribution when compared to Col-0 probably mirroring the fra2 root developmental defects. Features of fra2 GC walls include the presence of high-esterified pectic homogalacturonan and pectic arabinan, possibly to compensate for the reduced levels of callose, which was omnipresent in GCs of Col-0. Katanin severing of microtubules seems important in plant defense against M. incognita, with the nematode, however, to be nonchalant about this “katanin deficiency” and eventually induce the necessary GC cell wall modifications to establish a feeding site.

To date, it is mandatory for ecofriendly pest-management tools to be used in agriculture. Whey is a dairy-processing waste, a plant and soil chemical and fungicidal basic substance. The beneficial effect of whey on soil microorganisms, enzymatic activities, and free-living nematodes—combined with its toxic activity on the plant parasites—forms root knot nematodes. In this study, this finding is reported for the first time. A drip-irrigating tomato plant combined with whey in water at 3.125% (v/w) and 6.25% (v/w) dose dependently promoted Gram+ and Gram− bacteria, actinomycetes, and fungi biomass. Respectively, whey treatment and duration augmented the bacterial feeding nematodes along with the soil enzymatic activities, e.g., alkaline phosphatase, dehydrogenase, and urease. The counterpart for these soil organisms’ and enzymes’ functionality is the decomposition of organic matter, nutrient mineralization and cycling. Additionally, whey applied at 6.25% (v/w) every 10 days in a field experiment exhibited an efficacy of 70% on root knot nematodes. It is calculated that the EC50/3d value paralyzes in vitro Meloidogyne javanica, which was 3.2% (v/v). Conclusively, the soil application of whey could be a sustainable and ecofriendly method to combat the root knot nematodes and additionally to enhance soil biotic components.

The phytochemical investigation of the dichloromethane-soluble part of the methanol extract obtained from the fruits of Melia azedarach afforded one new tirucallane-type triterpene, 3-α-tigloylmelianol (1) and three known tirucallanes, melianone (2), 21-β-acetoxy-melianone (3), and methyl kulonate (4). The structure of the isolated compounds was mainly determined by 1D and 2D NMR experiments as well as HPLC-Q-TOF mass spectrometry. The cytotoxicity of the isolated compounds toward the human lung adenocarcinoma epithelial cell line A549 was determined, while no activity was observed against the phytonematode Meloidogyne incognita.

The biological diversity of nature is the source of a wide range of bioactive molecules. The natural products, either as pure compounds or as standardized plant extracts, have been a successful source of inspiration for the development of new drugs. The present work was carried out to investigate the cytotoxicity, antiviral and antimycobacterial activity of the methanol extract and of four identified limonoids from the fruits of Melia azedarach (Meliaceae). The extract and purified limonoids were tested in cell-based assays for antiviral activity against representatives of ssRNA, dsRNA and dsDNA viruses and against Mycobacterium tuberculosis. Very interestingly, 3-α-tigloyl-melianol and melianone showed a potent antiviral activity (EC50 in the range of 3-11μM) against three important human pathogens, belonging to Flaviviridae family, West Nile virus, Dengue virus and Yellow Fever virus. Mode of action studies demonstrated that title compounds were inhibitors of West Nile virus only when added during the infection, acting as inhibitors of the entry or of a very early event of life cycle. Furthermore, 3-α-tigloyl-melianol and methyl kulonate showed interesting antimycobacterial activity (with MIC values of 29 and 70 μM respectively). The limonoids are typically lipophilic compounds present in the fruits of Melia azeradach. They are known as cytotoxic compounds against different cancer cell lines, while their potential as antiviral and antibacterial was poorly investigated. Our studies show that they may serve as a good starting point for the development of novel drugs for the treatment of infections by Flaviviruses and Mycobacterium tuberculosis, for which there is a continued need.