Management Of Plant Parasitic Nematodes Research Articles

Management of Plant Parasitic Nematodes Associated with Walnut (Juglans regia L.) by using Organic Amendments

Management of Plant Parasitic Nematodes Associated with Walnut (Juglans regia L.) by using Organic Amendments

Biological approach for management of nematodes in banana

Field trial was conducted to evaluate the efficacy of biocontrol agent viz., AM fungi, Pseudomonus fluorescens, Paecilomyces lilacinus, Bacillus subtalis and Heterorhabditis indica for the management of plant parasitic nematodes around banana rhizosphere alone and in combination. The bioagents were applied around the banana rhizosphere at the time of planting, followed by three months after planting. One chemical check (carbofuran 3G) and an untreated check were maintained for comparison. Results obtained from three years of experimentation revealed that all the treatments significantly superior to the untreated check, increasing the plant growth parameters and yield of crops, and reducing the population of Meloidogyne incognita and Pratylenchus spp. Among the biocontrol agents, combined application of Pseudomonus fluorescens and Paecilomyces lilacinus (=Purpureocillium lilacinum) @ 12.5 g m−2 each were found to be the best in reducing the nematode population of M. incognita and Pratylenchus thornei, root knot index; and increasing the plant growth parameters and yield of banana.

Organic farming provides improved management of plant parasitic nematodes in maize and bean cropping systems

Intensification of agriculture, combined with poor agronomic practices have increased the incidence of plant parasitic nematodes (PPN) and other soil pathogens in East Africa, which consequently affects crop productivity in small holder farms. The objective of the study was to assess the effectiveness of farming systems in management of PPN and to recommend the best practice to farmers. Therefore, two field trials were established, one infarmer fieldsandoneon-station,usingmaize (Zeamays L.), intercroppedwithbeans(Phaseolusvulgaris L.) and in rotationwith beans as asole crop. Organic farming(that receivedcompost, Tithonia diversifolia and neem cake (Azadirachta indica)) was compared to conventional farming (that received fertilizer and nematicide), farmer practice (that received manure, Tithonia diversifolia and wood ash), and a farm with no input application (control). After threeyearsof continuouscultivation, twelve generaofPPNwere recovered fromsoiland/or root samples from the trials. Under inter- and sole-cropping at both sites, the abundance of PPN including Pratylenchus and Meloidogyne were significantly reduced in the organic system compared to the conventional, farmer practices and control. Organic farming was effective in reducing the genera of PPN below the control for a longer period (4 months) compared to conventional farming and farmer practice (2 months). The findings demonstrated the potential of organic farming in the suppression of PPN at the farmer level. Policy development and extension services can therefore consider organic farming as an alternative method in managing soil-borne nematodes in small holder farms in sub-Saharan Africa. However, further studies are required on other crops, in dry areas and the period to top-dress with organic amendments to assure effective suppression of PPN in organic farming.

Control and Management of Plant-Parasitic Nematodes in Integrated Production of Garden Strawberries (Fragaria×Ananassa Duchesne Ex Rozier)

AbstractArable soils are one of the most valuable natural resources and their long-term sustainable management is a determining factor in the integrated production of strawberries. It is well known that the current large-fruited garden strawberry (Fragaria × ananassa Duchesne ex Rozier) cultivars are more susceptible to many species of plant-parasitic nematodes and other plant pathogens. The aim of this study was to evaluate the effects of some cultural practices as potential methods for control of nematodes in the integrated production of strawberries. The investigation of the nematode populations was carried out in the region of western Balkan Mountains in Bulgaria (43°33'22.3"N 22°47'03.4"E), with cultivar ‘Maya’. In the surveyed area, plant protection products were applied under an approved scheme complying with the requirements for integrated fruit production (IOBC, IFP). Nematode populations were identified and classified to trophic level. The following genera of plant-parasitic nematodes were identified: Pratylenchus crenatus, P. neglectus, P. thornei, Tylenchorhynchus sp., and Paratylenchus spp. The density and species composition of plant parasitic nematodes were significantly reduced at the end of the study period comparing to the beginning of the study. From the results, it is clear that the integrated production can be defined as an economically feasible production of high quality fruits, giving priority to environmentally safe methods of pest control.

Nematode neuropeptides as transgenic nematicides.

Plant parasitic nematodes (PPNs) seriously threaten global food security. Conventionally an integrated approach to PPN management has relied heavily on carbamate, organophosphate and fumigant nematicides which are now being withdrawn over environmental health and safety concerns. This progressive withdrawal has left a significant shortcoming in our ability to manage these economically important parasites, and highlights the need for novel and robust control methods. Nematodes can assimilate exogenous peptides through retrograde transport along the chemosensory amphid neurons. Peptides can accumulate within cells of the central nerve ring and can elicit physiological effects when released to interact with receptors on adjoining cells. We have profiled bioactive neuropeptides from the neuropeptide-like protein (NLP) family of PPNs as novel nematicides, and have identified numerous discrete NLPs that negatively impact chemosensation, host invasion and stylet thrusting of the root knot nematode Meloidogyne incognita and the potato cyst nematode Globodera pallida. Transgenic secretion of these peptides from the rhizobacterium, Bacillus subtilis, and the terrestrial microalgae Chlamydomonas reinhardtii reduce tomato infection levels by up to 90% when compared with controls. These data pave the way for the exploitation of nematode neuropeptides as a novel class of plant protective nematicide, using novel non-food transgenic delivery systems which could be deployed on farmer-preferred cultivars.

Prevalence and diversity of plant parasitic nematodes in Northern Ireland grassland and cereals, and the influence of soils and rainfall

The prevalence and diversity of plant parasitic nematodes in Northern Ireland cereal and grassland was determined from 191 agricultural fields. A total of 18 nematode genera were detected, including economically important pests, Meloidogyne spp., Heterodera spp. and Pratylenchus spp., each of which were above economic damage thresholds in a significant proportion of the sites (92.4%, 70% and 28.6%, respectively). The detection of the root knot nematode, Meloidogyne minor (6% prevalence), was significant given its recent emergence across the turf grass sector and the prospect of M. minor becoming a common agricultural pest. Analyses of nematode prevalence and abundance highlighted significant associations with grass and cereals, soil types, soil grade (proxy for soil quality) and rainfall levels. Specifically, nematode populations varied between the two major soils (brown earths and gleys), while significant trends for increased nematode diversity and greater prevalence of both Meloidogyne and Pratylenchus with increasing rainfall were also observed. Multivariate analyses were performed to determine interactive effects and the relative importance of the factors affecting nematode populations. Notably, rainfall, in combination with either crop type or soil grade, had a significant effect on nematode abundance and diversity. The findings suggest significant changes in nematode populations have occurred over the last several decades and the possibility that these are linked to changing climate and cropping practices are discussed, as well as future concerns for plant parasitic nematode management.

Effect of temperature treatment on survival of Heterodera glycines and its associated fungi and bacteria

In studies of nematode-suppressive soil and plant-parasitic nematode management, it is often desirable to kill nematodes in the soil but keep the microbial community alive. The effect of temperature treatment on survival of Heterodera glycines, the soybean cyst nematode (SCN), and associated fungi and bacteria was investigated. Extracted eggs and cysts, and cysts in soil were subjected to treatments of temperatures ranging from −80 to 55°C for 1 to 24 h. Nematode survival was determined by hatching in vitro and by infectivity and development in soybean, and fungal survival was determined by plating the eggs or cysts on potato dextrose agar. The nematodes survived well between −20 and 45°C, but could not survive at −80 or 48°C and above, while some nematodes were killed after heat treatment of 46°C. By contrast, fungi survived well in the cysts at −80°C, and also much better than nematodes at the high temperatures. Glasshouse studies demonstrated that both bacteria and fungi survived well in the soil treated with −80°C. Transferring 5% of −80°C-treated soil to autoclaved soil could effectively establish nematode suppressiveness. Our study demonstrated that freezing soil at −80°C can kill SCN but maintain nematode suppressiveness, and the soil treatment can improve the method for nematode-suppressive soil evaluation.

Survey of Nematode-Destroying Fungi from Selected Vegetable-Growing Areas in Kenya

Plant-parasitic nematodes cause severe damage to a wide range of economic crops, causing upto 5% yield losses globally. In Kenya, vegetables are affected, among other pests, by parasitic nematodes, causing upto 80% loss in yield. Nematode control is very difficult and relies heavily on use of chemical nematicides. Use of these chemical nematicides leads to biological magnification, and elimination of natural enemies of other pathogens, thus creating a need for greater application of pesticides, increased production costs, and development of insecticide-resistance. These factors have led to a growing interest in search for alternate management strategies. The objective of this study was, therefore, to document nematode-destroying fungi in selected, major vegetable-growing areas in Kenya as a step towards developing a self-sustaining system for management of plant-parasitic nematodes. Soil samples were collected from five vegetable-production zones, viz., Kinare, Kabete, Athi-river, Machakos and Kibwezi, and transported to the laboratory for extraction of nematode-destroying fungi. The soil-sprinkle technique described by Jaffee et al (1996) was used for isolating the nematode-destroying fungi from soil, while, their identification was done using identification keys described by Soto Barrientos et al (2001). From this study, a total of 171 fungal isolates were identified as nematodedestroying. The highest population was recorded in Kabete, at 33.9% of the total, followed by Machakos, Kibwezi, Athi-river, with the least in Kinare, at 24.6, 22.2, 11.7 and 7.6% of the total population, in that order. Arthrobotrys was the most frequent genus, with mean occurrence of 7.3, followed by Monacrosporium with 6 and Stylophage with 5.2. A. dactyloides was significantly (P=0.002) affected by the agro-ecological zone, with the highest occurrence recorded in Kabete, and the least in Athi-river. Kibwezi recorded highest diversity index, with a mean of 1.017, while, Athi-river recorded the least, with a mean of 0.333. Kibwezi had the highest species richness, recording a mean of 3.4, while, the least mean of 1.6 was recorded in Athi-river. Mean species richness of 2.2 was recorded for both Kabete and Machakos, and 1.8 for Kinare. From the three genera recorded, Arthrobotrys was more effective at trapping nematodes compared to Monocrosporium and Stylopage. The genus Arthrobotrys had the highest number of trapped nematodes, with a total population of 57, followed by Monacrosporium, the least being Stylopage, with 45 and 36, respectively, in a period of 104 hours. From the study, it is evident that agricultural practices affect occurrence and diversity of nematodedestroying fungi, and, Arthrobotrys can be used as a bio-control agent for managing plant-parasitic nematodes.

Population changes of plant-parasitic nematodes associated with cover crops following a yam (Dioscorea rotundata) crop

Effective management of plant-parasitic nematodes affecting yams includes practices that can break the pest cycle from field to store. This study evaluated nematode population changes under cover crop cultivation following a main yam crop. Ten cover crops were planted after the harvest of the yam crop, in six different yam plots under natural nematode infestation. Soil and root samples were collected quarterly for nematode analysis from planting time for 12 months. Nematode data obtained were used to calculate prominence values as well as frequencies of occurrence for the nematode species identified. Statistical analyses was by ANOVA and Newman Keuls. Helicotylenchus spp. were the most frequently encountered and prominent nematodes followed by Pratylenchus spp. and Scutellonema spp., while Meloidogyne spp. ranked sixth in prominence. The most effective cover crops were Tagetes erecta, Aeschynomene histrix, Mucuna pruriens and Pueraria phaseoloides which reduced populations of the four aforementioned nematodes by 70, 39, 20, and 11 %, respectively. Lablab purpureus and Cajanus cajan hosted significantly higher nematode populations in their roots and rhizosphere soil samples than other cover crops. Populations of Meloidogyne were reduced with A. histrix, T. erecta, Crotalaria ochroleuca, Crotalaria juncea, P. phaseoloides, and M. pruriens. However, populations of Scutellonema and Pratylenchus were reduced with A. histrix, T. erecta, P. phaseoloides, and M. pruriens.

Survey of Nematode Destroying Fungi from Selected Vegetable Growing Areas in Kenya

Plant parasitic nematodes cause up-to 5% yield losses to a wide range of economic crops. In Kenya vegetables yield loss attributed to plant parasitic nematodes is estimated to 80%. Over the years, nematode control has heavily on the use of chemical nematicides which unfortunately leads to biological magnification and elimination of the beneficial microorganisms in the soil. This has triggered a growing interest in search of alternate management strategies. The objective of this study was, therefore, to document nematode destroying fungi in selected major vegetable growing areas in Kenya as a step towards developing self-sustaining system for management of plant parasitic nematodes. Soil samples were collected from five vegetable production zones in Kenya which were Kinare, Kabete, Athi-river, Machakos and Kibwezi and transported to the laboratory for extraction of the nematode destroying fungi. Soil sprinkle technique as described by Jaffee et al., (1996) was used to isolate the fungi from the soil while identification was done using identification keys described by Delgado et al.,(2001). From the study a total of 171 fungi isolates were identified as nematode destroying fungi. The highest population was recorded at Kabete area recording 33.9% of the total record, followed by Machakos, Kibwezi, Athi-river and the least in Kin are with 24.6, 22.2, 11.7 and 7. 6% of the total population in that order. Arthrobotrys was the most frequent genera with a mean occurrence of 7.3 followed by Monacrosporium with 6 and Stylophage with 5.2. A.dactyloides was significantly (P=0.002) affected by the agro-ecological zones with the highest occurrence being recorded in Kabete and the least in Athi-river. The highest diversity index and species richness of nematode destroying fungi was recorded in Kibwezi while the least was recorded in Athi-river. The genera Arthrobotrys had the highest number of trapped nematodes with a total population of 57, followed by Monacrosporium and least was Stylopage with 45 and 36 respectively, within a period of 104 hours. From the study, it is evident that agricultural practices affect the occurrence and diversity of nematode destroying fungi and Arthrobotrys can be developed as a bio-control agent for management of plant parasitic nematodes.

Incidence and management of plant parasitic nematodes under continuous vegetable production in a rainforest agroecology in Nigeria

SummaryField studies were conducted in 2012 and 2013 in the tropical rainforest zone of Nigeria to investigate the effects of a composted, pelletised organo-mineral fertiliser applied as an organic amendment at 5 metric tonnes (MT) ha-1 or at 10 MT ha-1 in four replications, on soil population densities of five genera of plant-parasitic nematodes and on crop yields of Telfairia occidentalis (fluted pumpkin). The experimental field was naturally infested with Meloidogyne incognita, Tylenchus spp., Helicotylenchus spp., Hirschmaniella spp., and Longidorus spp. The compost was applied as an amendment to soil planted with T. occidentalis 3 weeks after seedling emergence. At the end of both annual experiments, the addition of compost as a soil amendment resulted in 16.25 - 65.75% reductions in the populations of all five genera of plant-parasitic nematodes compared to an increase in each nematode population in the untreated control plots. There was also a higher crop yield of T. occidentalis in all eight treated plots compared to the control plots. Compost applied at 10 MT ha-1 reduced the soil populations of all nematode species significantly, with correspondingly higher yields of the crop compared to 5 MT compost ha-1 in both years of study. Correlation analysis showed that the population density of each nematode species had a negative effect on the cumulative leaf biomass (fresh weight) of the test crop. The results of this study suggest that nematodes constrained the production of T. occidentalis under continuous cropping and that a composted, pelletised organo-mineral fertiliser, applied as a soil amendment at 10 MT ha-1, suppressed soil populations of all five nematodes significantly and increased yields of T. occidentalis by 109 - 366% compared to the untreated control plots.

Evaluation of Organic Matter, Bio-inoculants and Inorganic Fertilizers on Growth and Yield Attributes of Tomato with Respect to the Management of Plant-Parasitic Nematodes

A field experiment was conducted to assess the effect of inoculations of biological nitrogen fixers using Azotobacter and Azospirillum individually and concomitantly with different recommended doses of inorganic nitrogen fertilizers and organic matter in the form of sesame (Sesame indicum) cake on the growth, yield and quality traits of tomato (Solanum lycopersicon L.) in relation to the management of plant-parasitic nematodes. The multiplication rate, egg masses, and root-galls per plant of these nematodes were reduced significantly by the individual inoculation of biological nitrogen fixers as well as with organic matter; while concomitant inoculation of bio-inoculants showed a synergistic effect in increasing crop growth and yield. Azospirillum was found to be more effective than Azotobacter. The highest improvement was recorded in the yield and growth parameters, plant height, fresh and dry weights, percent pollen fertility, green fruits yield per plant, chlorophyll content and ascorbic acid content when these biological nitrogen fixers were added concomitantly in various combinations. The Nitrogen-Phosphorus-Potassium (NPK) contents in plants and in soil increased considerably in almost all the combinations whenever these bio-fertilizers were inoculated and thus, reduce the fertilizers needed for commercial tomato production. The best results were obtained with 100% recommended dose of nitrogenous fertilizers along with the bio-fertilizers and farm yard manure.

The diverse nematicidal properties and biocontrol efficacy of Bacillus thuringiensis Cry6A against the root-knot nematode Meloidogyne hapla

Cry6A toxin from Bacillus thuringiensis is a representative nematicidal crystal protein with a variety of nematicidal properties to free-living nematode Caenorhabditis elegans. Cry6A shares very low homology and different structure with Cry5B, another representative nematicidal crystal protein, and probably acts in a distinct pathway. All these strongly indicate that Cry6A toxin is likely a potent candidate for nematicide. The present study dealt with global investigation to determine the detrimental impacts of Cry6Aa2 toxin on Meloidogyne hapla, a root-knot nematode, and evaluated its biocontrol efficacy in pot experiment. Obtained results indicated that Cry6Aa2 toxin exhibits obvious toxicity to second-stage juvenile of M. hapla, and significantly inhibits egg hatch, motility, and penetration to host plant. Pot experiment suggested that soil drenching with spore-crystal mixture of Cry6Aa2 can clearly lighten the disease of root-knot nematode, including reduction of galling index and egg masses on host plant root, decreasing final population of nematode in soil. Moreover, application of Cry6Aa2 can obviously promote plant growth. These results demonstrated that Cry6Aa2 toxin is a promising nematicidal agent, and possesses great potential in plant-parasitic nematode management and construction of transgenic crop with constant resistance to nematode.

Synergism between urea and urease-positive bacteria in controlling root-knot nematodes

Synergistic effects between urea and urease-positive bacteria against root-knot nematodes were assayed in laboratory and greenhouse trials. We isolated 85 urease-positive bacterial strains from soil, compost, sludge, and animal faeces; they belonged to four clades and sixteen genera of Eubacteria based on 16S rRNA BLAST. Twenty-five representative strains were assessed for nematicidal and urease activities. The urease-positive bacteria were nematicidal. A cubic relationship with a critical threshold was found between a strain’s nematicidal and urease activities. Sixteen strains with urease activity above this threshold had a 100 % nematicidal activity level. These 16 strains and urea alone were assessed for urease activity in pot experiments with tomato, which found that high-dose urea was nematicidal to root-knot nematodes (400–800 mg per kg soil) and phytotoxic (1,600 mg), while low-dose urea (≤200 mg) was non-nematicidal. However, nematodes could be controlled at 200 mg urea per kg soil in combination with urease-positive bacteria from seven different strains, and the nematode control efficacy of urea was always non-linearly positively correlated with soil urease activity. To test bacterial persistence, soils were recycled for another experiment, in which nine strains were significantly nematicidal, with a stronger relationship between nematode control efficacy and soil urease activity. These results suggest ways to manipulate soil bacteria to improve soil urease activity for the management of plant-parasitic nematodes. While urease-positive bacteria may have practical applications in controlling nematodes, their use will require careful field investigation and appropriate environmental safety evaluation.

Yield losses by Phytonematodes: challenges and opportunities with special reference to Egypt

Plant-parasitic nematodes (PPN) constitute a major constraint to agriculture.Estimates of their crop-loss are important for establishing research, extension, andbudget priority. Regulatory policy action, pesticide impact assessment, resourceallocation, and program prioritization are usually contingent upon such crop lossdata. Recent questionnaire results of important PPN genera and estimates of croplosses in Egypt due to PPN are presented herein. Crop losses due to thenematodes on 80 crops, 15 of which are ‘life sustaining’, were estimated at L.E.15.85 (= $2.30) billion annually based on 2011-2012 Egyptian production figuresand prices. Crop loss estimates of vegetables, fruits, and field crops demonstratedstaggering figures and therefore nematode problems warrant considerably moreeffort and support than they are currently receiving. Current challenging nematodeissues include reduced number of effective nematicides available and limitation intheir use due to environmental issues, increased adoption of intensive agriculture,climate change, occurrence of resistance-breaking PPN pathotypes oneconomically important crops, and potential introduction of quarantine-nematodes.Therefore, basic and applied nematological research should be more oriented toprovide better management of plant-parasitic nematodes in an economically andenvironmentally beneficial manner.

Management of Plant-parasitic Nematodes by the Use of Botanicals

Management of Plant-parasitic Nematodes by the Use of Botanicals Plant-parasitic nematodes are causing great damage to agricultural and horticultural crops. Hence, biopesticides of botanical origin have become focus of attention today for facing the nematode problems in an eco-friendly manner. The use of botanical pesticides is now emerging as one of the prime means to protect crops. In India, botanical pesticides are available in many plants for which deep search and testing is required as many of them are still unexplored.

Nematicidal isochromane glycoside from Kigelia pinnata leaves

Synthetic nematicides such as oxamyl and carbofuran play significant roles in the management of plant-parasitic nematodes. However, their negative environmental impacts have it imperative to search for safer alternatives. As part of our contribution in the search for bio-nematicides, compounds from plant extract were screened for possible potent nematicidal agent. A new isochromane carboxylic acid glycoside, isolated from the leaves of Kigelia pinnata (Lam.) Benth (Bignoniaceae) was evaluated for its nematicidal activity. The structure of the proposed compound was characterized by various spectroscopic methods, which included UV, FTIR, 1D-, and 2D-NMR, FAB-MS, TOF-ESI-MS and TOF-ESI-MS/MS (TANDEM). The in vitro experiment conducted on the glycoside against Meloidogyne incognita juveniles and eggs indicated an induced mortality. Its activity can be compared favourably with oxamyl, when tested at 0.1 mg/mL concentration. At four hours of observation, no significant difference (P < 0.05) between oxamyl and the glycoside was observed. The present data sustains that natural glycoside is a promising oxamyl alternate for controlling nematode-induced plant root knots and may contribute to integrated pest management.

Soil Nematodes of Brassica rapa: Influence of Temperature and pH

An investigation of the soil nematodes associated with Brassica rapa and the effects of temperature and pH on their populations was carried out. The nematodes recovered were categorized into three ecologically functional groups; Nitrogen Releasing Nematodes (NRN, bacterial- and fungal- feeders), Plant-Parasitic Nematodes (PPN), and Pest Suppressor Nematodes (PSN, Carnivorous or predatory (Ca) and Omnivorous (Om), nematodes). While over 67% of the NRN were bacterial feeding nematodes (Ba 2 ), dominated by Plectus and Acrobeloides; over 65% of the PPN were contributed by the Pl 3 nematodes dominated by Helicotylenchus mucronatus and Rotylenchus buxophilus ; and the PSN were dominated (over 63%) by the omnivores (Om 4 ; Mesodorylaimus and Dorylaimus). Populations of all the nematode categories recovered fluctuated significantly (P < 0.01) during the sampling period. All the nematode groups were similarly weakly negatively correlated with pH and temperature. Approximately 1000 H. mucronatus nematodes/100 mL of soil was recorded. This is 10x the value for which the management of PPN is recommended. The entire soil nematode food web structure was represented in the nematodes recovered, all groups of nematodes responded similarly to environmental changes, all groups of nematodes tended to be acidophilic and thermophobic, and the PPN could potentially be a threat for profitable B. rapa production.

Identification of neuropeptides, flp-1 and flp-12 targeting neuromuscular system of rice root knot nematode (RRKN) Meloidogyne graminicola.

Root-knot nematodes (RKNs), Meloidogyne spp, are found in all temperate and tropical areas, and are among the most damaging plant pathogens worldwide. M. graminincola is an economically important root parasite on upland, lowland and deepwater rice. FMRFamide-like peptides (FLPs) play significant role as neurotransmitters or neuromodulators in the nervous system and proposed as one of the important targets for the plant parasitic nematode management. Therefore, for the first time, we have cloned and characterized two neuropeptide genes (flp-1 and flp-12) from the cDNA of preparasitic second stage juveniles of M. graminicola. The flp-12 contains putative 22 residue long signal peptide at N-terminal suggesting function as an extra-cellular protein. We have found highly conserved motif LFRGR in flp-1. These two flp genes could be interesting and potential targets for functional validation to explore their utility for designing management strategies.

Plant parasitic nematode relative abundance and population suppression under Chromolaena odorata (Asteraceae) fallow

An experimental investigation into the suppressive potential of the shrub Chromolaena odorata (L.) (Asteraceae) (also known as “Siam Weed” or “Jack-in-the-Bush”) fallow to the management of plant parasitic nematodes was undertaken between April 2008 and April 2010. The experiment involved comparing nematode population densities in: (i) pure planted fallow of C. odorata, (ii) a mixture of C. odorata with other weeds, and (iii) natural re-growth of weeds from the seed bank in the soil in the field with C. odorata excluded. The population densities of several nematode species were determined at the outset, and then at 6-month intervals for 24 months. The nematode taxa identified as being present prior to fallowing were Meloidogyne spp. (Heteroderidae), Pratylenchus spp. (Pratylenchidae), Helicotylenchus spp., Rotylenchulus spp. (Hoplolaimidae); Rhabditids (Rhabditidae) and Dorylaimus spp. (Dorylaimoidea). Chromolaena odorata fallow significantly reduced the population densities of Meloidogyne spp., Pratylenchus spp., and Helicotylenchus spp. after 2 years of fallow, by 77.2%, 75.3% and 81.3% respectively. Under natural re-growth, reduction in populations of Meloidogyne spp., Pratylenchus spp., and Helicotylenchus spp. ranged between 0.12% and 17%. Densities of non-parasitic species (Rhabditids and Dorylaimus spp.) significantly increased under both C. odorata + natural re-growth fallow. However, a 16% increase in the population density of Rotylenchulus spp. was observed under C. odorata fallow in contrast to a significant (54.1%) reduction observed under the natural re-growth fallow. Bush fallow with C. odorata may become part of an integrated management practice in the management of nematode pests in crop production by indigenous farmers in south-western Nigeria.