Javanica Juveniles Research Articles

Nematicidal activity of <i>Ageratum conyzoides</i> leaf extract against root-knot nematode (<i>Meloidogyne javanica</i>) on eggplant in Jalingo, Nigeria

Devastation of crops by pests is exacerbated by human activities but nature provides remedies that are environmentally friendly. This study was carried out to evaluate the activity of A. conyzoides leaf extract against Meloidogyne javanica on eggplant in Jalingo, Nigeria. Three concentrations (crude extract, 5 ml and 10 ml dilutions) of extract of Ageratum conyzoides as well as control (no application) were applied on juveniles and eggs of M. javanica in petri dishes in the laboratory in 2018 and 10 ml of the same extract was applied into holes at the base of eggplants transplanted into a nematode-infested field in 2018 and 2019. Result of the juvenile mortality test showed that the extract treatments caused the mortality of M. javanica juveniles with crudes extract being highest at 90.3%. Results of the egg hatch inhibition test also showed the extract treatments significantly reduced egg hatch compared to control with crude extract having the highest inhibition of 85.5%. Field experiment in both years indicated that the extract treatments recorded significantly (P˂0.05) better result than control in all parameters in both years. There was reduced root galling and nematode reproduction and by extension final nematode population with attendant high yield in extract-treated plants. It is therefore concluded that A. conyzoides has the potential for use as a bio-pesticide against M. javanica.

Comparative Effectiveness of Filamentous Fungi in Biocontrol of Meloidogyne javanica and Activated Defense Mechanisms on Tomato.

The nematicidal potential of five filamentous fungi as biological control agents (BCAs) against the root-knot nematode (RKN), Meloidogyne javanica, infecting tomato was assessed in vitro and in pot experiments. The five promising native taxa, namely Trichoderma longibrachiatum, T. harzainum, T. asperellum, Lecanicillium spp., and Metacordyceps chlamydosporia, were selected to compare their effectiveness against both chemical (Mocap, 10% ethoprophos) and biological (abamectin) nematicides on M. javanica reproduction indices and plant growth parameters. The stimulation of defense mechanisms was assessed by monitoring changes in the enzymatic activities of the polyphenol oxidase (PPO), peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT), lipid peroxidation (MDA), phenols, and proteins content of tomato roots. The laboratory assays revealed that T. longibrachiatum, M. chlamydoporia, and Lecanicillium spp. seemed to be the most effective under laboratory conditions, with more than 60% of juvenile mortality. The egg infection rate was above 62%, and the egg hatching rate was below 32%. The direct parasitism by the five taxa was confirmed by scanning electron microscope observation. The results of this study found a similar parasitism mechanism for T. longibrachiatum, T. harzianum, and M. chlamydosporia, where their hyphae and spores adhered to the M. javanica juveniles cuticle layer and formed trapping rings around them. The pot experiment results showed that T. harzianum and Lecanicillium spp. enhanced the plant growth parameters. Trichoderma longibrachiatum, abamectin, and the ethoprophos-based nematicides effectively decreased the reproduction rates of the nematode. The Trichoderma species and M. chlamydosporia significantly reduced the gall index and female fecundity of RKN. The treatment with BCAs and chemical nematicides involved a significant increase in the antioxidant activities of nematode-infected plants. The ethoprophos and fungal treatments decreased the MDA and total phenols content compared with the nematode-infested seedlings. This paper analyzes the advancements made towards the effective and efficient biocontrol of M. javanica using different fungal taxa, especially T. longibrachiatum and M. chlamydosporia, and the implications of these advancements for sustainable agriculture and food security.

Response of Meloidogyne javanica to Silver Nanoparticle Liquid from Agricultural Wastes

Plant-parasitic nematodes attack is an important problem on crop production worldwide. Meloidogyne javanica is a potentially damaging pest of several crops. Laboratory studies were conducted to examine the effect of supernatant liquid from the synthesis of silver nanoparticles with agricultural wastes on the survival and hatching of Meloidogyne javanica juveniles and eggs. The experiment consisted of five treatments (carbofuran, corn cobs, rice husk, guinea corn chaff, and distilled water served as control) at three concentrations of 10, 20, and 30%. Each was repeated three times in a complete randomized design. Nematicidal bioassay revealed a consequential (p=0.05) decrease in egg hatch rate in 20 and 30% concentrations of the nanoparticle supernatant liquid. Similarly, percentage mortality increased significantly (p=0.05) in the nano supernatant liquid, with the corncob silver nanoparticle having the highest percentage mortality. These results confirmed that the agricultural waste silver nanoparticle supernatant liquid could be a cost-effective and eco-friendly nematicide.

Bio-fertilizers\u2019 protocol for controlling root knot nematode Meloidogyne javanica infecting peanut fields

BackgroundPlant parasitic nematodes create serious threat to crop production. In Egypt root knot nematode, Meloidogyne spp. has been considered to be a limiting factor in the production of most crops of which the Peanut (Arachis hypogaea L.) is an important legume and oil crop. Therefore, management of root knot nematodes Meloidogyne spp. is an obligatory challenge. Microbial organisms are extensively used as eco-friendly tools for controlling plant parasitic nematodes as alternative to chemical nematicides. The effectiveness of the commercial bacterial bio-fertilizers NPK containing Bacillus polymyxa, B. circulance, B. megaterium, Pseudomans spp.; the nitrogen fixative bacteria Azotobacter chroocoocum and the bacterial isolate NRC211 were evaluated against the root knot nematode, Meloidogyne javanica infecting peanut plants under field conditions. Identification of the bacterial isolate was made through PCR amplification and sequencing of 16S rDNA gene.ResultsSequencing of 16S rDNA gene revealed that the bacterial isolate NRC211 had 100% similarity with Bacillus wiedmannii strain FSL W8-0169 16S ribosomal RNA. This Bacillus was recorded for the first time under accession number LC626774 on GenBank data base as B. wiedmannii NRC211. Recorded data revealed that all the tested treatments whether single or combined in soil naturally infested with M. javanica, resulted in variable significant reduction in the nematode reproductive parameters with a considerable increase in crop production and oil content of peanut plant. These results were improved by increasing the frequency of application of the bio-agents. In this respect the repeated combined treatment of A. chroococcum and B. wiedmannii NRC211 treatment overwhelmed all other treatments in decreasing nematode reproductive parameters with percentage reductions of 94.8, 79.0 and 80.1% in M. javanica juveniles in soil, galls and egg masses, respectively. This was associated with slight increase in peanut oil content than the untreated control. The repeated combined treatment of NPK plus A. chroococcum produced the highest increase 608.7%, and 72.7% in crop production and plant growth parameters, respectively than the control. While, the oil content in this treatment was increased up to 47.4 g/kg.ConclusionIt was concluded that B. wiedmanni NRC211 is an eco-friendly bio agent that can be applied with other commercial microbial bio-fertilizers in bio-integrating programs for controlling M. javanica infecting peanut plants.

Tomato Divinyl Ether-Biosynthesis Pathway Is Implicated in Modulating of Root-Knot Nematode Meloidogyne javanica's Parasitic Ability.

The role of the 9-lipoxygenase (9-LOX)-derived oxylipins in plant defense is mainly known in solanaceous plants. In this work, we identify the functional role of the tomato divinyl ether synthase (LeDES) branch, which exclusively converts 9-hydroperoxides to the 9-divinyl ethers (DVEs) colneleic acid (CA) and colnelenic acid (CnA), during infection by the root-knot nematode Meloidogyne javanica. Analysis of LeDES expression in roots indicated a concurrent response to nematode infection, demonstrating a sharp increase in expression during the molting of third/fourth-stage juveniles, 15 days after inoculation. Spatiotemporal expression analysis using an LeDES promoter:GUS tomato line showed high GUS activity associated with the developing gall; however the GUS signal became more constricted as infection progressed to the mature nematode feeding sites, and eventually disappeared. Wounding did not activate the LeDES promoter, but auxins and methyl salicylate triggered LeDES expression, indicating a hormone-mediated function of DVEs. Heterologous expression of LeDES in Arabidopsis thaliana rendered the plants more resistant to nematode infection and resulted in a significant reduction in third/fourth-stage juveniles and adult females as compared to a vector control and the wild type. To further evaluate the nematotoxic activity of the DVEs CA and CnA, recombinant yeast that catalyzes the formation of CA and CnA from 9-hydroperoxides was generated. Transgenic yeast accumulating CnA was tested for its impact on M. javanica juveniles, indicating a decrease in second-stage juvenile motility. Taken together, our results suggest an important role for LeDES as a determinant in the defense response during M. javanica parasitism, and indicate two functional modes: directly via DVE motility inhibition effect and through signal molecule-mediated defense reactions to nematodes that depend on methyl salicylate.

Leaf antioxidant machinery stimulation by Meloidogyne javanica infestation: A case study on Cucumis melo seedlings

Following nematode infestation, leaf-localized responses are vital not only as early infection signs but also as an indication of actions required to preserve crop productivity. In this context, the leaf-level physiological responses of cantaloupe seedlings were evaluated after 40 consecutive days of cultivation under different Meloidogyne javanica juveniles (J2s) inoculation regimes (0, 100, and 850 J2s plant−1). Leaf growth parameters and photosynthetic pigments (chlorophyll, carotenoids) content were not affected by J2s infestation, while foliar Potassium concentration significantly declined. The RuBIsCo activase gene expression was negatively associated with the J2s inoculation level. Total flavonoids, total phenolics, lipid peroxidation indexes, phenylalanine ammonia-lyase activity, as well as, ascorbate peroxidase gene transcription, were higher in the inoculated plants (regardless of the J2s inoculant level). Taken together, present data indicate that J2s infestation impacts primarily the Potassium levels in leaves. Additionally, a substantial stimulation of the plant antioxidant machinery (independent of the nematode infestation intensity) is triggered. Finally, it was established that the transcriptional regulation of the RuBIsCo activase 1 gene under biotic stress has the capacity to be employed as a potential stress indicator marker.

Biocontrol potential of nematophagous fungi against Meloidogyne spp. infecting tomato

Root-knot nematodes are the most economically damaging group of plant parasitic nematodes. Intensive agriculture on sandy soil of Moroccan agroecosystems results in a prevalence and wide distribution of Meloidogyne spp., limiting both conventional and organic fruit and vegetable production. The aim of this study is to assess the nematicidal potential of twelve local isolates of nematophagous fungi in organic tomato production in laboratory and greenhouse conditions. Fungal isolates were of seven genera: Paecilomyces, Purpureocillium, Trichoderma, Fusarium, Talaromyces, Arthrobotrys, Dreschslerella, and Monacrosporium. In vitro assays screened the isolates for their ability to immobilize Meloidogyne javanica juveniles using 96-well tissue culture plates at a concentration of 106 spores.ml−1. The same isolates were tested for their potential to reduce M. javanica populations and galling on tomato roots in pot experiments with infested soil, applied upon transplantation at 107 spores.ml−1. Average mortality rate of second-stage juveniles of Meloidogyne spp. in vitro ranged from 11 to 42%, with a maximal range of 64 to 73% mortality. The highest rates of mortality were recorded after 72 h using Purpureocillium lilacinum and Arthrobotrys oligospora. In pot experimentation, the reproduction rate of root-knot nematodes ranged from 176 to 5920% with the gall index varying from 2.7 to 4.9 in treated pots. This study identified Paecilomyces and Arthrobotrys direct nematicidal effect against Meloidogyne spp., in laboratory conditions. To achieve successful control, further studies should be conducted to identify the optimal range of environmental factor practices which lead to the enhancement of biocontrol activity of these NF in the field.

Nematicidal Activity of phytocompounds from Piliostigma thonningii Stem Bark Against Meloidogyne javanica

The study investigated nematicidal activity of phytocompounds isolated from Piliostigma thonningii mature stem bark. Compounds were extracted from the stem bark using solid–liquid extraction. Column chromatography was used to separate the phytocompounds and structures were characterized by LC–MS/MS QTRAP. Nematicidal activity of P. thonningii fractions were evaluated against second stage juveniles (J2) of Meloidogyne javanica. One tetracyclic diterpenoid (1), one glucosinolate (2), and two glycosylated flavonoids (3) and (4) that have strong nematicidal activity against second stage M. javanica juveniles from P. thonningii mature stem bark were identified. Nematicidal activity of the four compounds ranged from 59–99%. Compound 3 exhibited excellent nematicidal activity, 99 ± 1% that was comparable to that of the positive control fenamiphos at 100 mg/ml dose. Its activity increased from 79–99% as concentration was changed from 20 to 100 mg/ml. The results of the present study shows that P. thonningii mature stem bark consist of phytocompounds that have potent nematicidal activity therefore, they could be associated in an integrated pest management program after further investigations.

Τhe Nematicidal Potential of Bioactive Streptomyces Strains Isolated from Greek Rhizosphere Soils Tested on Arabidopsis Plants of Varying Susceptibility to Meloidogyne spp.

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.

Parasitus fimetorum and Macrocheles muscaedomesticae (Acarina:Parasitidae, Macrochelidae) as Natural Predators of the Root Knot Nematode, Meloidogyne javanica Treub

The potential use of two predacious mites, Parasitus fimetorum (Berlese 1904) and Macrocheles muscaedomesticae (Scopoli 1972), for controlling the root knot nematode, Meloidogyne javanica Treub 1885 was evaluated under laboratory and semi-field conditions. Obtained results revealed that the 2 predators significantly reduced the root knot nematode numbers. In addition, the highest reduction percentage (57.24%) in nematode juveniles was recorded at the treatment of (1000 nematode + 10 mites). For M. muscaedomesticae, the highest mortality percentage (50.83%) in nematode juveniles was recorded at the treatment of (1000 nematode + 50 mites), followed by (1000 nematodes + 20 mites) 48.88%, while the treatment of (1000 nematode + 10 mites) gave (47.13%). The combination of the 2 mite species (1000 nematodes + 50 mites/species) caused the highest mortality percentages in nematode juveniles (69.29%), followed by (1000 nematodes + 20 mite/species) 50.51% and the treatment of (1000 nematode + 10 mite/species) (37.66%). At the pot experiments, the highest overall mortality percentage in M. javanica juveniles was recorded at the treatment of P. fimetorum + M. muscaedomesticae giving (57.07%), followed by the treatment of P. fimetorum (39.17%), and then, by M. muscaedomesticae alone that recorded only (17.47%). In conclusion, predacious mites can be partially considered a control tool of the parasitic nematodes.

Sensitivity to fluensulfone of inactivated Meloidogyne spp. second-stage juveniles.

Nonfumigant nematicide efficacy is affected by several factors, such as nematode species and environmental conditions. However, the influence of nematodes' physiological status on nematicide efficacy is unknown. Inactive nematodes, such as those in quiescence or dormancy, seem to be more tolerant to nematicides than active ones. Second-stage juveniles of Meloidogyne species were inactivated by low temperatures and reversible nematicides before and during exposure to fluensulfone. The sensitivity of inactive juveniles to fluensulfone the nematicide was compared to that of active juveniles by EC50 (median effective concentration) for juvenile immobilization and root gall reduction. Inactivating Meloidogyne hapla and Meloidogyne javanica juveniles at 5 °C increased the EC50 (median effective concentration) of fluensulfone for immobilization of and root galling by Meloidogyne spp. 3.6 to 9.5 times. When the exposure temperature was decreased from 25 to 15 °C, EC50 for M. javanica root gall reduction after 24 and 48 h exposure increased 3.1 and 4.9 times, respectively, whereas for M. hapla, it increased 2.3 and 2.0 times, respectively. Juveniles of M. javanica and M. incognita immobilized by fenamiphos were as sensitive to fluensulfone as active juveniles based on the number of root galls. However, juveniles of these species immobilized by fluopyram were more tolerant to fluensulfone than untreated active juveniles. An interaction of fluopyram and fluensulfone activities is suggested. Changes in the sensitivity of inactive Meloidogyne spp. juveniles to fluensulfone depend on the inactivation method. Fluensulfone could be better applied when nematodes are active in the soil. © 2020 Society of Chemical Industry.

Nematophagous mushrooms can be an alternative to control Meloidogyne javanica

Tomato is a vegetable of great economic importance; however, it is extremely affected by nematodes of the genus Meloidogyne. Control of these nematodes can be performed using nematophagous fungi. Some of these nematophagous fungi are mushrooms, in which the production residue has potential to control nematodes. In this context, the aims for this study were to verify: i) the ovicidal, nematicidal and nematistatic potential of metabolites retained in the liquid mushroom culture medium on Meloidogyne javanica; ii) the ovicidal, nematicidal and nematistatic potential of the aqueous extract of culture substrates of mushroom species on M. javanica and iii) the interaction of the mushroom mycelium and M. javanica juveniles. Twenty-four mushroom isolates distributed in 15 different species were tested, being cultivated in liquid medium and sawdust, and their respective filtrates and extracts were then used as treatments for M. javanica. Statistical analysis was performed using the chi-square test, comparing the frequencies of treatments with controls. In this work, the control potential of M. javanica with the use of mushrooms was verified. Lentinula edodes, Macrocybe titans and Pleurotus eryngii isolates presented potential to control M. javanica in all tests performed.

Biological activities and chemical composition of Pistacia lentiscus in controlling Fusarium wilt and root-knot nematode disease complex on tomato

The experiments were carried out under laboratory and greenhouse conditions to study the biocontrol potential of aqueous extracts of Pistacia lentiscus (L.) at different concentrations (C5: 100%, C4: 75%, C3: 50%, C2: 25%, C1:10% w/v) against Meloidogyne javanica and Fusarium oxysporum f.sp. lycopersici. In vitro assays, showed that the inhibition rate of F. oxysporum growth increased progressively by increasing the extract concentration, reaching about 83% at the highest concentration C5. However, the fungi growth rate (VC: mm/h) and the spore germination rate correlated negatively with the extract concentration. The results showed that M. javanica juvenile mortality increased significantly with all tested concentrations of plant extract after 72 h of exposure time. Furthermore, C3, C4 and C5 increased similarly the net mortality (C3: 96%, C4: 97%, C5: 96%) of M. javanica juveniles. Egg hatching decreased significantly with the increase of concentration of P. lentiscus aqueous extracts. The lowest level of egg hatching was recorded with C5 (38.2%). Furthermore, the P. lentiscus extract promoted the growth of tomato plant and reduced the incidence of wilt disease complex on tomato seedlings. The phytochemical analysis showed the high phenolic (quinic and gallic acids) and flavonoids (quercetin) content and antioxidant activity of the P. lentiscus extract. The considerable biocidal activities and valuable chemical composition suggested the future application of this plant in new bio-pesticides formulation.

Management of Fusarium oxysporum f. sp. lycopersici and root-knot nematode disease complex in tomato by use of antagonistic fungi, plant resistance and neem

ABSTRACTSimultaneous infestation with root-knot nematodes (RKN) and Fusarium oxysporum f. sp. lycopersici (FOL) leads to formation of a disease complex that increases crop losses than effect of either RKN or FOL. In this study a management programme involving plant resistance, biological control agents, and neem was carried out to manage RKN and fusarium wilt disease complex. The biological control agents were Purpureocillium lilacinum (PL) and Trichoderma harzianum (TH) while the RKN was Meloidogyne javanica. In vitro dual culture plates were set up to test the interaction of biological control agents and FOL. Greenhouse experiments were conducted using two tomato cultivars Rambo F1 and Prostar F1. The treatments were; PL, TH, PL–TH, neem, PL neem, TH neem, and PL–TH neem. Each treatment was replicated four times and the treatments set up in a randomised complete block design in the greenhouse. Inhibition of FOL mycelial growth by TH and PL was 51.9%, and 44% respectively by the ninth day in vitro culture plates. In the cultivar, Prostar F1, the treatments PL–TH, PL, and TH in the presence or absence of neem had a FOL disease severity score significantly lower than the untreated control. Host resistance sufficed to prevent infection of Rambo F1 with FOL. The treatments PL–TH, PL and TH reduced FOL propagules and M. javanica juveniles in the roots and performed even better when combined with neem in both tomato cultivars. Therefore, a host that is resistant combined with biological control agents and organic amendments can be used in the management of RKN and FOL in tomato production.

Diversity of nematophagous fungi in Moroccan olive nurseries: Highlighting prey-predator interactions and efficient strains against root-knot nematodes

Plant-parasitic nematodes are major pests in agriculture. Microbial antagonists such as nematophagous fungi are of great interest for developing alternative biocontrol strategies to replace nematicide use. This study aims to isolate, identify and assess the diversity and the in vitro predatory activity of nematophagous fungi from various olive nurseries in Morocco. A total of 305 soil samples were collected in 25 nurseries in Moroccan olive-producing areas (Jbala, Guerouane, Haouz and Souss). Seventy-three pure fungal strains from nematophagous fungi were recovered from nursery substrates infested with root-knot nematodes. Diversity indices showed that fungi were more numerous in southern regions, whereas fungal communities were more numerically alike in northern regions, partly depending on the occurrence of root-knot nematodes. One fungal strain, Talaromyces assiutensis, killed all Meloidogyne javanica juveniles during in vitro predation tests. Orbiliaceae (Arthrobotrys spp., Drechslerella brochopaga, Monacrosporium spp.) trapped 50 to 80% of juveniles. Purpureocillium and Trichoderma species killed 30 to 50% of juveniles. The diversity of nematophagous communities could be affected by the north-south climate gradient of Morocco, by their nematode prey expansion, and, to a lesser extent, by the habitat origin of the substrates used. Talaromyces assiutensis was the most efficient nematophagous species against M. javanica. The use of native nematophagous fungi is a promising alternative strategy for nematode control in olive nurseries and to prevent nematode introduction into olive orchards.

Biocidal effects of Piper hispidinervum (Piperaceae) essential oil and synergism among its main components

In this study we evaluated the effect of a pressure gradient (1–2 atm) in the extraction and composition of the essential oil (EO) of Piper hispidinervum by steam distillation. We also evaluated the insect antifeedant effects (Spodoptera littoralis, Leptinotarsa decemlineata, Myzus persicae and Rhopalosiphum padi) and nematicidal activity (Meloidogyne javanica) of the oils, their major components and their synergistic interactions. Safrole was the major component (78–81%) followed by terpinolene (5–9%). The EOs tested were effective insect antifeedants. Safrole, explained most of the insect antifeedant action of P. hispidinervum EOs. When safrole and terpinolene were tested in binary combinations, low ratios of safrole improved the antifeedant effects of terpinolene. P. hispidinervum EOs caused higher mortality of M. javanica juveniles than their major components. In binary combinations, low ratios of terpinolene increased the nematicidal effects of safrole. The EO treatment strongly suppressed nematode egg hatching and juvenile infectivity. P. hispidinervum EOs affected the germination of S. lycopersicum and L. sativa mostly at 24 h of treatment, being L. sativa the most sensitive. Safrole moderately affected germination and root growth of L. sativa, S. lycopersicum and L. perenne. Terpinolene only affected S. lycopersicum root growth.

Effects of Plant Leaf Extracts on Egg-Masses Hatching and Juveniles Mortality of the Root-Knot Nematode, Meloidogyne Javanica

The effects of plant extracts from fresh leaves of five different plants; Acasiaarabica, Ziziphusspina christi, Eucalyptus camaldulensis, Lawsonia inermis andDalbergia sissoo were evaluated against egg-masses hatching and juvenilemortality of root-knot nematode, Meloidogyne javanica under laboratory conditions.Results revealed that, all treatments extracts had significantly (P < 0.05) reduced inthe hatching of egg-masses. The maximum reduction occurred in Acasia arabicawith the concentration (S) was (97.13%) and the concentration (S/2) was (89.99%),whereas the minimum reduction caused by Ziziphusspina christi with theconcentration (S) was (45.49%) and the concentration (S/2) was (24.63%). Thesame effects of plant extracts against M. javanica juveniles, the most mortality ofsecond stage juveniles was observed in leaf extracts of Acasia arabica, andDalbergiasissoo with the concentration (S) was (100%) as regarding to and theconcentration (S/2) was (100%) in Dalbergia sissoo, while the least in Ziziphusspinachristi with the both concentrations S and S/2 (17.0 and 5.33%), respectively.

Nematicidal activity of crambe extracts on Meloidogyne spp.

Alternative methods for the control of nematodes, such as the use of plant secondary metabolites, can be explored for integrated pest management systems. The objective of this work was to assess the best solvent for obtaining allyl isothiocyanate from Crambe abyssinica leaves, and the effects of this extract on Meloidogyne incognita and M. javanica. Dry leaves of C. abyssinica at 200 mg L-1 were used to prepare extracts by using water (by infusion and grinding), acetone, water + ethanol (hydroalcoholic extraction), methanol, hexane, and chloroform as solvents. Following the evaporation of the solvents, the residue was resuspended in water for use in the experiments. Distilled water and chemical nematicide were used as control treatments. Once the most effective extracts were defined, the following dosages of dried crambe leaves were used: 0, 200, 300, 400, and 500 mg L-1. High performance liquid chromatography (HPLC) was used to quantify the allyl isothiocyanate present in the extracts. After the solvents evaporated, the residues were eluted with water and used in assays with 200 eggs for the hatching test or 200 second stage juveniles (J2) for mobility and mortality tests. The hydroalcoholic extract was the most effective in reducing the hatching of M. incognita and M. javanica juveniles, by 71.6 and 74.4 percentage points, respectively. The mortality of M. incognita and M. javanica in the hydroalcoholic extract was 93.2 and 64.4%, respectively, followed by the methanol extract (17.6 and 34%) and the extract obtained by grinding (9.2 and 28%). The hydroalcoholic extract at 250 mg L-1 showed high nematicidal effect. The HPLC analysis of the extracts revealed that only the methanol and hydroalcoholic extracts had allyl isothiocyanate, indicating that the inhibitory effects on the hatching, mobility, and mortality were not solely attributed to the presence of this compound.

Sisal leaf decortication liquid residue for controlling Meloidogyne javanica in tomato plants

The effect of sisal liquid residue (fresh and fermented) was evaluated in controlling the root-knot nematode (Meloidogyne javanica) in tomato plants. Bioassays were conducted in vitro with 100 µL of an aqueous suspension containing 300 juveniles (J2) of M. javanica and 1000 µL of sisal liquid residue. The treatments consisted of nematode immersion for 24 and 48 hours in sisal liquid residue, fresh or fermented, diluted in water to the final concentrations of 0, 2.5, 5, 7.5, 10, 12.5, 15, 17.5 and 20%, and nematicide Carbofuran at 350 mg of the active ingredient per liter. Under greenhouse conditions, 4000 juveniles of M. javanica were inoculated on tomato plants grown in pots, and after one week, 100 mL of sisal liquid residue at concentrations of 0, 4, 8, 12, 16 and 20%, were added to soil around the tomato plants. Control treatments received either 100 mL of distilled water or 0.5 g of Carbofuran per pot. Forty days after inoculation, plants were harvested and evaluated for plant growth and root damage. In addition, the selective effect of sisal liquid residue on growth of beneficial soil microorganisms was evaluated. All concentrations of sisal liquid residue presented nematicidal effect, after 48 h of nematode exposure. A mortality rate of 100% was obtained for M. javanica juveniles exposed to liquid residue at a concentration of 20%. Application of increasing concentrations of both sisal liquid residues reduced the number of galls and egg masses per plant and per gram of roots, as well as the final population of M. javanica in soil. Growth of beneficial soil microorganisms was observed in soil amended with sisal fresh liquid residue, for all concentrations tested. The fermented residue caused inhibition of soil beneficial microorganisms. Future studies should be conducted to test the nematicidal effect on tomato plants under field conditions.

Nematicidal activity of allyl bromide and dibromo(nitro)methane under laboratory conditions.

Restrictions on soil fumigants are prompting the development of new compounds for controlling nematodes, other soilborne pathogens and weeds. We evaluated the nematicidal activity of five bromine compounds against Meloidogyne javanica in vitro, and tested the two most effective ones against Pratylenchus penetrans and Xiphinema index in vitro and in soil. Only allyl bromide and dibromo(nitro)methane showed nematicidal activity against M. javanica juveniles in vitro at <320 mg L(-1) . Allyl bromide killed M. javanica and P. penetrans at 20 mg L(-1), and X. index at 10 mg L(-1), whereas 320 mg dibromo(nitro)methane L(-1) was required to kill P. penetrans. Allyl bromide also showed higher nematicidal activity than dibromo(nitro)methane against M. javanica and P. penetrans in soil. Allyl bromide at 40 and 20 mg L(-1) soil eliminated root galls and nematode eggs on tomato roots grown in M. javanica-inoculated loess and sandy soils respectively, showing higher nematicidal activity than 1,3-dichloropropene. No P. penetrans were recovered from soil treated with 80 mg allyl bromide L(-1) soil or 320 mg dibromo(nitro)methane L(-1) soil. Allyl bromide showed high nematicidal activity against all three nematode species, and nematicidal activity of dibromo(nitro)methane was discovered. These compounds could serve as new fumigation nematicides, pending further experiments.