Phytochemistry in the development of pesticides and biocides

To date biopesticides and biocides are studied as substitutes for their toxic synthetic ancestors. The botanical pesticides are evaluated as tools intended for integrated crop protection schemes, while the natural biocides for their potential use in residential areas. In this study we evaluate various botanical matrixes for the nematicidal properties against the root knot nematode Meloidogyne spp., in the form of pastes and extracts for soil amendment as well as plant secondary metabolites isolated from the afore mentioned matrixes and used individually or in binary mixtures to create synergism. The effects of the treatment compound/s are evaluated in various growth stages of the parasite, considering physiology and behavior. Additionally we investigate the use of botanical extracts as natural biocides for the control of toxic cyanobacteria Aphanizomenon gracile in fresh waters. A first attempt is made to formulate a natural algicidal compound into a slow release product that could permit a long lasting biological activity and thus higher efficacy under open air condition

Whey: The Soil Bio-Community Enhancer That Selectively Controls Root-Knot Nematodes

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

Nematicidal Activity and Phytochemistry of Greek Lamiaceae Species

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

Biofunctional properties of Melia azedarach extracts

Melia azedarach is a botanical species on the focus of global research for its biological properties. It is usually used for its timber as well as a shade tree. This deciduous tree is a Meliaceae species that, unlike Azadirachta indica, adapts in various tropical and warm temperate regions around the world and has thus gradually gained scientific interest. The secondary metabolites it contains exhibit various biological properties, belong to different chemical categories and can be extracted from various plants parts. The appliance of such knowledge is of interest in medicine and agriculture, while analytical methods and extraction procedures serve as tools for identification and quantification of similar substances in other complex botanical matrixes. To date the discovery of novel alternative methods for diseases and pest control are mandatory, due to resistance problems and toxicity management to non target organisms

The efficacy and the chemical composition of natural products of plant origin with the potential of use against the root knot nematodes (Meloidogyne incognita) in greenhouse cultures

Ten botanical species have been studied for their nematicidal activity against the root-knot nematode M. incognita. The chemical composition of the extracts used, for the nematodes control, was determined as well. Lamiaceae: the essential oils of eight greek aromatic plants were extracted and studied, namely: Melissa officinalis, Sideritis clandestina, Origanum dictamnus, Ocimum basilicum, Mentha pulegium, Origanum vulgare, Vitex agnus castus and Salvia officinalis. Strongly nematicidal were found: Origanum vulgare, Origanum dictamnus, Mentha pulegium and Melissa officinalis. The EC₅₀/₉₆h values were calculated at 1.5, 1.7, 3.1 and 6.1 μl ml⁻¹ respectively. The strong activity was attributed to the high contents of carvacrol according to GC-MS analysis. Carvacrol together with two other monoterpenes, namely carvon and geraniol, provoked 100% paralysis when tested alone at concentrations of 0.5 μl ml⁻¹. On the contrary 1,8 cineol and limonene tested alone did not exhibit high nematicidal activity. Meliaceae: two species were studied namely: Azadirachta indica & Melia azedarach. The formulated nematicide AzaNema® 1 % EC as well as the technical grade azadirachtin 11.8 % (commercial extract of A. indica) were used. The registered formulated product’s dose 6 1 ha⁻¹ was initially expressed as 0.2 μg a.i ml⁻¹ and 0.03 μg a.i g according to Weber et al., 2000, for the microwell and pots experiments performance, in water and soil respectively. Fosthiazate was used as control, at its registered dose as well. Both azadirachtin products were not nematicidal at the registered dose, even though azadirachtin residues in the test solutions remained stable throughout biological experiments according to HPLC analysis. Grind lyophilized fruits of the species Melia azedarach as well as a polar (methanol) and non polar (hexane) extract were tested against M. incognita. The EC50 value for methanol extract in microwells was calculated at 0.04 % (w/v) and in pots at 0.9 % (w/w). Additionally, the EC₅₀ value for the grind lyophilized fruits in pots was calculated at 0.4 % (w/w). In the search for active ingredients in the melia methanol extract, chromatographic techniques were established for its limonoids separation (TLC and Column Chromatography) and purity control (HPLC). Their identification was performed with ¹H and ¹³C NMR analysis. The mass error was calculated with a LC/MS Q-TOF analysis. The mass spectra of the limonoids were also identified, using LC/MS analysis.Στην παρούσα εργασία μελετήθηκε η νηματωδοκτόνος δράση 10 βοτανικών ειδών εναντίον του κομβονηματώδη M. incognita και προσδιορίστηκε η χημική σύσταση των εκχυλισμάτων που χρησιμοποιήθηκαν στην καταπολέμηση. Τα βιολογικά πειράματα αφορούσαν στην πρόκληση παράλυσης σε προνύμφες δευτέρου σταδίου ανάπτυξης (J2) του M. incognita, που είναι το μολυσματικό στάδιο του βιολογικού του κύκλου, καθώς και στην επίδραση στον βιολογικό κύκλο εντός της ρίζας προσβεβλημένων φυτών τομάτας. Οι βοτανικές οικογένειες που μελετήθηκαν ήταν η Lamiaceae και η Meliaceae που περιέχουν βιολογικά ενεργά συστατικά, τα τερπενοειδή (μονο- και σεσκιτερπενοειδή) και τα λιμονοειδή (τετρανορτριτερπενοειδή) αντίστοιχα. Σε ότι αφορά τα Lamiaceae, μελετήθηκαν για την ικανότητα παράλυσης σε J2 τα αιθέρια έλαια, και κάποια συστατικά τους τερπένια, που απομονώθηκαν από τα εξής οκτώ ελληνικά αρωματικά φυτά: Melissa officinalis, Sideritis clandestina, Origanum dictamnus, Ocimum basilicum, Mentha pulegium, Origanum vulgare, Vitex agnus castus και Salvia officinalis. Πλέον δραστικά βρέθηκαν τα αιθέρια έλαια των ειδών O. dictamnus, O. vulgare, M. pulegium και M. officinalis για τα οποία υπολογίστηκαν οι τιμές EC₅₀. Η υψηλή αποτελεσματικότητα των αιθέριων ελαίων του O. vulgare και O. dictamnus, αποδόθηκε στην υψηλή τους περιεκτικότητα σε καρβακρόλη ενώ αντίστοιχα ισχυρά νηματωδοκτόνα μεμονωμένα συστατικά τερπένια αποδείχθηκαν η καρβόνη και η γερανιόλη. Αντίθετα το λιμονένιο και η 1,8-κινεόλη παρουσίασαν χαμηλή αποτελεσματικότητα. Από τα Meliaceae μελετήθηκαν δύο είδη και συγκεκριμένα το Azadirachta indica & το Melia azedarach. Μελετήθηκε η δραστική ουσία αζαδιραχτίνη, που περιέχεται στο είδος Azadirachta indica, με τη μορφή τόσο του τεχνικώς καθαρού προϊόντος όσο και του σκευάσματος AzaNema® 1 % EC, εγκεκριμένου ως νηματωδοκτόνο, στη συνιστώμενη δόση του για καταπολέμηση των κομβονηματωδών, σε πειράματα παράλυσης J2 και επίδρασης στο βιολογικό κύκλο του νηματώδη. Διαπιστώθηκε αδυναμία ελέγχου του M. incognita που οφείλεται κύρια στην μη επαρκή δραστικότητα της αζαδιραχτίνης στη δόση αυτή και όχι στην αστάθεια του σκευάσματος ή σε διαφορές από την αναγραφόμενη εγγυημένη του σύνθεση, αφού με βάση τη χημική ανάλυση του η περιεκτικότητα της αζαδιραχτίνης στο σκεύασμα βρέθηκε σταθερή, η αναμενόμενη από την ετικέτα. Τέλος, μελετήθηκε το Melia azedarach υπό τη μορφή ενσωματωμένων αλεσμένων καρπών και εκχυλισμάτων και βρέθηκε να προκαλεί παράλυση σε J2 και να αναστέλλει την ολοκλήρωση του βιολογικού κύκλου σε δόσεις χαμηλές. Στo πλαίσιo μιας προσπάθειας συσχέτισης της νηματωδοκτόνου δράσης του εκχυλίσματος του Melia azedarach εναντίον του M. incognita, έγινε απομόνωση και ταυτοποίηση των λιμονοειδών εκείνων που συμμετείχαν σε μεγαλύτερη αναλογία στη σύσταση του. Οι τεχνικές που χρησιμοποιήθηκαν για το χρωματογραφικό διαχωρισμό και την ταυτοποίηση ήταν η χρωματογραφία λεπτής στοιβάδας (TLC), η χρωματογραφία στήλης (CC), η τεχνική υγρής χρωματογραφίας υψηλής απόδοσης (HPLC), η τεχνική υγρής χρωματογραφίας με φασματoμετρία μάζας (LC-MS), η τεχνική υγρής χρωματογραφίας υψηλής ακρίβειας με φασματόμετρο μάζας με υβριδικό αναλυτή τετράπολου–χρόνου πτήσης (Q-TOF) και η τεχνική πυρηνικού μαγνητικού συντονισμού ¹H και ¹³C (NMR)

Short-Time Impact of Soil Amendments with Medicago Plant Materials on Soil Nematofauna

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