Nematode Population Densities Research Articles

Estimation of prevalence and population densities of banana nematodes in Kondotty-local Government Area, Kerala State, India

Estimation of prevalence and population densities of banana nematodes in Kondotty-local Government Area, Kerala State, India

Biological control of Heterodera glycines by spore-forming plant growth-promoting rhizobacteria (PGPR) on soybean

Heterodera glycines, the soybean cyst nematode, is the most economically important plant-parasitic nematode on soybean production in the U.S. The objectives of this study were to evaluate the potential of plant growth-promoting rhizobacteria (PGPR) strains for mortality of H. glycines J2 in vitro and for reducing nematode population density on soybean in greenhouse, microplot, and field trials. The major group causing mortality to H. glycines in vitro was the genus Bacillus that consisted of 92.6% of the total 663 PGPR strains evaluated. The subsequent greenhouse, microplot, and field trials indicated that B. velezensis strain Bve2 consistently reduced H. glycines cyst population density at 60 DAP. Bacillus mojavensis strain Bmo3 suppressed H. glycines cyst and total H. glycines population density under greenhouse conditions. Bacillus safensis strain Bsa27 and Mixture 1 (Bve2 + Bal13) reduced H. glycines cyst population density at 60 DAP in the field trials. Bacillus subtilis subsp. subtilis strains Bsssu2 and Bsssu3, and B. velezensis strain Bve12 increased early soybean growth including plant height and plant biomass in the greenhouse trials. Bacillus altitudinis strain Bal13 increased early plant growth on soybean in the greenhouse and microplot trials. Mixture 2 (Abamectin + Bve2 + Bal13) increased early plant growth in the microplot trials at 60 DAP, and also enhanced soybean yield at harvest in the field trials. These results demonstrated that individual PGPR strains and mixtures can reduce H. glycines population density in the greenhouse, microplot, and field conditions, and increased yield of soybean.

Effects of Fertilizer, Nematicide, and Tillage on Plant–Parasitic Nematodes and Yield in Corn and Soybean

Core Ideas Tillage decreased plant–parasitic nematode population densities during portions of the study. Fertilizers did not help manage plant–parasitic nematode population densities. Manure application increased both corn and soybean yields. Soybean response to NPK and NPKS was more positive in a lower yielding environment. Soybean cyst nematode (SCN, Heterodera glycines) is the most damaging pathogen of soybean [Glycine max (L.) Merr.] in the United States and plant–parasitic nematodes such as Pratylenchus (lesion nematode) and Helicotylenchus (spiral nematode) commonly infect corn (Zea mays L.). There are few management options for these nematodes, so understanding how common agronomic practices affect these nematodes is critical. Therefore, a series of 2‐yr experiments were conducted in corn and soybean production. Long‐term conventional tillage (CT) and minimum tillage (MT) treatments were in place at the study site. Fertilizer and granular nematicide—for assessing crop damage by nematodes—treatments were applied: (i) untreated control, (ii) NPK, (iii) NPKS, (iv) liquid swine manure, (v) nematicide without fertilizer, and (vi) NPKS with nematicide. Lesion nematode and SCN densities were greater in MT than CT during portions of the study, but tillage did not affect spiral nematodes. Corn yield was 8% greater in CT than MT in the first phase of the rotation, but tillage did not significantly affect soybean yield. None of the fertilizers—manure, NPK, or NPKS—reduced plant–parasitic nematode densities compared to control. Manure consistently increased corn and soybean yields. The NPK and NPKS were beneficial for corn, but inconsistent for soybean yields. There was some evidence that soybean yield response to fertilizers was greater in more stressed environments, such as with more SCN pressure. Because nematicide efficacy was inconsistent, it was not possible to make a definitive measurement of crop damage by plant–parasitic nematodes in this study.

Influence of cucurbitacin-containing phytonematicides on selected nutrient elements in leaf tissues of green bean under greenhouse conditions

ABSTRACTCucurbitacin-containing phytonematicides consistently reduce nematode population densities in various crops. However, there is no information on how these products affect the accumulation of essential nutrient elements in crops. The objective of this study was to determine the influence of Nemafric-BL and Nemarioc-AL phytonematicides on accumulation of essential nutrient elements in leaf tissues of green bean (Phaseolus vulgaris L.) under greenhouse conditions. Weekly application of phytonematicides each at 0%, 2%, 4%, 8%, 16% and 32%, were assessed on plant growth variables, nematode suppression and nutrient elements (Ca, K, Na, Fe, Zn) in leaf tissues of green bean at 56 days after initiating the treatments. Phytonematicide concentrations significantly (P ≤ 0.05) affected nematode numbers and nutrient elements, without affecting plant growth. Calcium (R2 = 0.97), K (R2 = 0.93), Na (R2 = 0.94) and Fe (R2 = 0.91) each with increasing Nemafric-BL phytonematicide concentration exhibited positive quadratic relations. In contrast, K (R2 = 0.97) and Fe (R2 = 0.98) each with increasing Nemarioc-AL phytonematicide concentration exhibited positive quadratic relations, whereas Na (R2 = 0.92) and Zn (R2 = 0.72) each with increasing phytonematicide concentration exhibited negative quadratic relations. In conclusion, accumulation of essential nutrient elements in green bean leaf tissues and increasing phytonematicide concentrations exhibited density-dependent growth patterns prior to the eventual expression of plant growth responses.

Genetic variation and population dynamics of the cereal cyst nematode, Heterodera filipjevi in wheat areas of Bolu, Turkey

The cereal cyst nematode, Heterodera filipjevi (Madzhidov) Stelter, was detected in Turkey in 1996 and since then it has been increasingly reported to cause losses in wheat yields. Cereal cyst nematode populations have a wide genetic diversity which makes it difficult to be managed. The objectives of this research were to investigate the genetic variation of 23 cyst nematode populations collected from wheat growing areas of Bolu Province, utilising sequenced ITS-rDNA regions, and monitoring main nematode isolate population dynamics in field conditions. The results of ribosomal DNA sequencing revealed that all cyst populations were H. filipjevi and that little genetic variation was present among populations. The highest number of second-stage juveniles was observed between April and beginning of May in a field experiment; white females were visible on the roots in late May. The hatching process was positively correlated with low temperatures, but there were inverse correlations between reproductive factors and initial nematode population densities.

Relationship between soil organic matter and nematodes in sugarcane fields

Sugarcane plays an important socio-economic role in northeastern Brazil. However, the low yield in this region is associated with several factors (e.g. frequent occurrence of plant-parasitic nematodes). In order to observe the influence of soil organic matter on the nematodes, this study aimed to characterize the spatial nematode distribution in a sugarcane field. The study was carried out in Goiana - Pernambuco State (Brazil), fifty days after sugarcane cutting (10 days after vinasse application). The sampling scheme consisted of a regular 60 × 50-m grid, 10 m spaced, through 0 to 0.2 m depth. Spatial distribution was evaluated by semivariograms fit and performed by ordinary kriging interpolation for mapping. Exponential and spherical models promoted the best fit to semivariograms, resulting in ranges from 16 to 19 m. There was a strong negative correlation between soil organic matter and plant-parasitic nematode population density. Free-living nematodes had a similar distribution pattern as soil organic matter content. These results indicated that soil organic matter had important effects on spatial distribution of both plant-parasitic and free-living nematodes.

SOIL NEMATODES IN FOREST BIOCENOSES OF PROTECTED AREAS IN REPUBLIC OF KARELIA

Soil nematode communities of coniferous and deciduous forests in protected areas of the Republic of Karelia were studied with regard to their latitudinal position. A series of parameters (taxonomic diversity, nematode population density, eco-trophic structure and ecological indices of soil food web) were used to assess the nematode communities. The highest nematode taxonomic diversity was observed in linden forests and the lowest one in soils of pine forests. Bacterial-, fungal feeders and nematodes associated with plants dominated the soil nematode community structure in all types of forest biocoenoses. According to ecological indices of the food web (SI, EI), the soil ecosystems were assessed as undisturbed, with complex trophic linkages and a moderate level of soil organic enrichment. One exception was northern taiga forests in Kostomukshsky Strict Nature Reserve, where low SI values indicated an impact of detrimental environmental factors on the soil ecosystems. It was found that the main distinction of northern deciduous forests from southerner ones is the diversity and relative abundance of plant parasitic nematodes. It was for the first time demonstrated here that the graphic triangle constructed from ecological indices of the food web can be effectively applied to identify the features of soil nematode communities specific to forest type and local habitat conditions.

Reaction of soybean cultivars to the root-knot nematode Meloidogyne javanica

Meloidogyne javanica is one of the main nematodes that attack soybean crops and although genetic resistance is the ideal control measure, few cultivars are described as resistant among the innumerous cultivars recommended for the Central Region of Brazil. In this context, we aimed to evaluate the reaction of 29 soybean cultivars to M. javanica . Two experiments were conducted under greenhouse conditions in a completely random­ized design with six replications. The plants were inoculated with a suspension of 2000 eggs and J2 of M. javanica and the evaluations occurred sixty days after the inoculation (DAI), determining the nematode population density and the reproduction factor. Based on the results from these two experiments we conducted another experiment selecting four soybean cultivars, one moderately resistant and three with an unknown behavior. These cultivars were inoculated with different concentrations of M. javanica inoculum. The experiment was conducted in a completely randomized design in a 4 x 4 factorial scheme with twelve replications. Evaluations were carried out at 10 DAI by observing the number of J2 and J3/ root system. At 45 DAI the nematode population density in the roots was evaluated. Of the soybean cultivars tested, none behaved as resistant. However, the cultivars UFU Carajas and BRSGO Paraiso presented less M. javanica development in the roots compared to the P98Y70 and NS 7478 and as the inoculum pressure was increased, the penetration and development of the nematode in the roots increased.

First Report of Meloidogyne ethiopica Parasitizing Sugarcane in Brazil

HomePlant DiseaseVol. 101, No. 4First Report of Meloidogyne ethiopica Parasitizing Sugarcane in Brazil PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Meloidogyne ethiopica Parasitizing Sugarcane in BrazilC. Bellé, S. M. Kulczynski, P. R. Kuhn, R. M. D. G. Carneiro, I. Lima-Medina, and C. B. GomesC. Belléhttp://orcid.org/0000-0003-2247-3207Search for more papers by this author, S. M. KulczynskiSearch for more papers by this author, P. R. KuhnSearch for more papers by this author, R. M. D. G. CarneiroSearch for more papers by this author, I. Lima-MedinaSearch for more papers by this author, and C. B. GomesSearch for more papers by this authorAffiliationsAuthors and Affiliations C. Bellé , Doutorando em Fitossanidade, Universidade Federal de Pelotas, 96010-900, Pelotas, RS, Brazil S. M. Kulczynski , Universidade Federal de Santa Maria, Frederico Westphalen, 98400-000, RS, Brazil P. R. Kuhn , EPAGRI, 89893-000, Mondaí, SC, Brazil R. M. D. G. Carneiro , Embrapa Recursos Genéticos e Biotecnologia, 70770-91, Brasília, DF, Brazil I. Lima-Medina C. B. Gomes , Embrapa Clima Temperado, 96010-971, Pelotas, RS, Brazil. Published Online:27 Jan 2017https://doi.org/10.1094/PDIS-09-16-1303-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Root-knot nematodes (Meloidogyne spp.) cause serious damage to sugarcane (Saccharum spp.) plantations in different growing regions of Brazil (Bellé et al. 2014). In December 2013, sugarcane plants (cvs. RB835486, RB72454, and Nova Irai) exhibiting many galls in the roots were detected and sampled in areas from Frederico Westphalen (27°34′S, 53°34′W), Vicente Dutra (27°19′S, 53°39′W), and Caiçara (27°28′S, 53°40′W) municipalities, northwest Rio Grande do Sul State, Brazil. No symptoms were observed in the aerial part of infected sugarcane plants. Individual Meloidogyne females were extracted from the root samples and used for species identification by electrophoresis (n = 40) according to the technique described by Carneiro and Almeida (2001). Subsequently, egg masses from the females of each sample were inoculated on to tomato plants (cv. Rutgers) for later complementary studies: perineal morphology (n = 20/sample) and measurement of second stage juveniles (J2) (n = 20/sample). Species identification was confirmed by PCR species-specific SCAR using a primer set meth-F (5′-ATGCAGCCGCAGGGAACGTAGTT-3′) and meth-R (3′-TGTTGTTTCATGTGCTTCGGCATC-5′) (Correa et al. 2014). In addition, the root samples were processed to determine the number of Meloidogyne eggs and J2s. The nematode population densities in the samples ranged from 320 to 621 eggs plus J2/5 g of roots. The isozyme electrophoresis analyses revealed the esterase phenotype E3 (Rm = 0.92, 1.15, 1.32) that is typical for Meloidogyne ethiopica Whitehead 1968. The female perineal patterns showed moderately high to high dorsal arch, thick and separated striae from mild to wavy, and an undivided lateral field, similar to the one in M. ethiopica redescription. The juvenile mean body length was 480.42 ± 10.1 μm, the stylet length was 11.7 ± 0.3 μm, and the tail length 63.9 ± 0.8 μm, with 12.1 to 14.9 μm long hyaline region. The PCR-SCAR product was ∼350 bp, which was previously reported only for M. ethiopica (Correa et al. 2014). The esterase phenotype, species-specific SCAR, morphometric and morphological characteristics in all Meloidogyne populations studied here were consistent with those reported for M. ethiopica (Carneiro et al. 2004; Correa et al. 2014; Whitehead 1968). In greenhouse tests, sugarcane plants cv. RB72454 maintained in pots with sterilized soil were inoculated with 5,000 eggs plus J2s of the original population of M. ethiopica using six replicates; a noninoculated control was included. Seventy days later, all inoculated plants showed symptoms of stunting, a reduced fresh weight of shoots and roots, and a decrease in plant height of about 60% compared with the noninoculated control. Galling symptoms on the roots were similar to those in the field, and the nematode reproduction factor (final population/initial population) was 16.6. The noninoculated plants did not exhibit galls and their development was not affected. These results confirmed the pathogenicity of M. ethiopica on sugarcane. This is the first report of M. ethiopica parasitizing sugarcane roots worldwide, and this finding has great importance for Brazilian agriculture, considering this nematode may damage sugarcane plants and become an additional problem for this crop.

Reaction of soybean cultivars to Meloidogyne incognita race 3

Soybean crops are attacked by several pathogens. Among these, there are nematodes of the Meloidogyne genus, which are responsible for yield reduction. Among several control methods against these pathogens, one consists of using resistant cultivars. The objective of this study was to evaluate the reaction of 27 soybean cul­tivars to the nematode Meloidogyne incognita race 3. Two experiments were conducted under greenhouse conditions, in a completely randomized design, with 27 treatments and six replications. Plants were kept in plastic cups with capacity for 400 mL of sterilized substrate (soil + sand) and were artificially inoculated with a suspension of 2000 eggs and J2 of M. incognita race 3/plant. Evaluations were performed sixty days after in­oculation (DAI), in order to determine nematode population density in the roots and reproduction factor (RF). Through experiment results, four soybean cultivars were selected, of which three were resistant (BRSGO Pa­raiso, NA 7255 RR and NS 7490 RR) and one was susceptible (BRSGO Santa Cruz). The cultivars aforemen­tioned were inoculated with four different M. incognita Race 3 inoculum concentrations. Thus, an experiment was conducted in a completely randomized design, in a 4 x 4 factorial, with 12 replications. Evaluations were performed at 10 DAI, when the number of J2 and J3/root system was observed. At 45 DAI, nematode popula­tion density in the roots was evaluated. NS 7476, NS 7490 RR, NA 8015 RR, NA 7620 RR, BRSGO Graciosa, P98Y70, CD 237 RR, P98Y51 and UFU Milionaria cultivars showed resistant behavior, as they were similar to the resistance standards used. NA 7255 RR and NS7490 RR cultivars behaved as M. incognita race 3-resistant with the use of the inoculum concentration of 4000 eggs/plant, which seems to be the ideal concentra­tion to evaluate the reaction of cultivars to this nematode. Evaluations of M. incognita race 3 penetration in the roots were not a good parameter to evaluate cultivar behavior.

Responses of the citrus nematode population densities post-application of Nemarioc-AL phytonematicide and aldicarb synthetic nematicide

Density-dependent growth patterns suggested that under phytonematicides population densities of plant-parasitic nematodes could either be stimulated, neutral or inhibited, thereby resulting in ‘inconsistent results' concept. The objective of this study was to determine whether post-application sampling of the citrus nematode (Tylenchulus semipenetrans Cobb) population densities under untreated control, Nemarioc-AG phytonematicide and aldicarb on rough lemon (Citrus jambhiri Lush. ) seedlings could provide quantitative evidence of ‘inconsistent results'. Uniform three-month old C. jambhiri seedlings in plastic pots containing 2700 ml growing mixture were each inoculated with 10000 T. semipenetrans eggs and second-stage juveniles (J2). A week after inoculation, seedlings were split into three groups of seventy each and subjected to once-off treatment of untreated control, 2 g Nemarioc-AG phytonematicide and 2 g aldicarb. Five seedlings from each group were randomly placed on greenhouse benches to serve as a sampling block, with a total of 14 blocks. The entire block was sampled on a weekly basis and assessed for final nematode population density (Pf). After the final assessment, Pf under untreated control over increasing sampling intervals exhibited positive quadratic relations, with the model explaining 90% associations, with optimum Pf of 13804 eggs and J2 at six weeks post-application. In contrast, Pf over increasing sampling intervals under phytonematicide and aldicarb exhibited negative quadratic relations, with the model explaining 95 and 92% associations, respectively. The two had minimum Pf at 974 eggs and J2 and 2205 eggs and J2, respectively, each at approximately six weeks. In conclusion, opposite temporal cyclic nematode population growth patterns post-application of nematicidal products and untreated control provided empirically-based evidence of ‘inconsistent results' in nematode management under phytonematicides.

Suppressive Effects of Organophosphate Nematicides on Nematode Population Density and Yield Loss of Potato in a Field Infested with Potato Cyst Nematode

Suppressive Effects of Organophosphate Nematicides on Nematode Population Density and Yield Loss of Potato in a Field Infested with Potato Cyst Nematode

Sampling Error in Relation to Cyst Nematode Population Density Estimation in Small Field Plots

Cyst nematodes are serious plant-parasitic pests which could cause severe yield losses and extensive damage. Since there is still very little information about error of population density estimation in small field plots, this study contributes to the broad issue of population density assessment. It was shown that there was no significant difference between cyst counts of five or seven bulk samples taken per each 1-m2 plot, if average cyst count per examined plot exceeds 75 cysts per 100 g of soil. Goodness of fit of data to probability distribution tested with χ2 test confirmed a negative binomial distribution of cyst counts for 21 out of 23 plots. The recommended measure of sampling precision of 17% expressed through coefficient of variation (cv) was achieved if the plots of 1 m2 contaminated with more than 90 cysts per 100 g of soil were sampled with 10-core bulk samples taken in five repetitions. If plots were contaminated with less than 75 cysts per 100 g of soil, 10-core bulk samples taken in seven repetitions gave cv higher than 23%. This study indicates that more attention should be paid on estimation of sampling error in experimental field plots to ensure more reliable estimation of population density of cyst nematodes.

Non-phytotoxic concentration of cucurbitacin-containing phytonematicides and the overall sensitivities to Swingle citrumelo seedling rootstock

Nemarioc-AL and Nemafric-BL phytonematicides contain cucurbitacins A and B active ingredients, respectively. The major drawback of the two products had been their phytotoxicity to various crops, which was resolved using the Curve-fitting Allelochemical Response Data (CARD) computer-based model, which also provided overall sensitivities (Σk) of the plant to the test phytonematicides. Two of the seven biological indices were adapted to provide the non-phytotoxic concentration, technically referred to as the Mean Concentration Stimulation Point (MCSP)-which is product-specific and crop-specific. The objective of this study was to determine MCSP of Nemarioc-AL and Nemafric-BL phytonematicides on Swingle citrumelo seedling rootstock and the related Σk of the rootstock to the phytonematicides. Six-months-old seedlings were subjected on weekly basis to 0, 2, 4, 8, 16, 32 and 64% for each phytonematicide. At 84 days after the treatments, MCSP values for Nemarioc-AL and Nemafric-BL phytonematicides on seedlings were 2.97 and 5.6%, with Σk values of 3 and 2 units, respectively. In conclusion, both phytonematicides had MCSP and Σk values which suggested that the two products would be suitable for use on Swingle citrumelo seedling rootstock as a supplement for managing nematode population densities in citrus production.

Suppression effects of nematode population density by the cropping of newly bred southern root-knot nematode resistant sweetpotato cultivars

Suppression effects of nematode population density by the cropping of newly bred southern root-knot nematode resistant sweetpotato cultivars

Intra- and interplot variability of Heterodera glycines population densities in experimental settings to soybean variety evaluations in Nebraska

The intra- and interplot variability of soybean cyst nematode (SCN; Heterodera glycines) population densities was characterized in three experimental areas in Nebraska in 2014. Through single-core cluster sampling of 4-m-long plots, a random pattern of SCN incidence (number of SCN-positive soil cores out of 10 per plot) within plots was suggested by the binomial distribution in one location. The detected randomness, however, was associated to the high SCN infestation level and tillage in the experimental area. In the other two experimental areas, the beta-binomial distribution adequately described SCN incidence (index of aggregation θ > 0; index of dispersion D > 1.0), suggesting the presence of an aggregated pattern within plots. Based on the properties of the fitted distributions, the intraplot aggregation of incidence affects the probability of cyst recovery during sampling and thereby the estimation of SCN population densities. At the interplot scale, correlogram analysis of 36 transects of 28 and 35 m showed that discrete foci of SCN population densities were spatially dependent with foci located up to 15 m away. This was confirmed by spatial autocorrelation, which indicated that SCN population densities in the 4-m-long plots were positively correlated with population densities of up to two contiguous plots. Interplot aggregation of SCN population densities suggests lack of independence among plots or experimental units. Altogether, the results of this study recommend that researchers conducting field experiments with H. glycines consider SCN spatial pattern, particularly, if rigorous comparisons among soybean varieties are sought. Consideration may comprise both the diagnostics of spatial dependence of SCN population densities in a prospective variety evaluation site, prior to spring sampling, and the subsequent allocation of varieties to plots based on their degree of spatial correlation. While limited to a single-year assessment, the information on SCN spatial pattern from the present study, coupled with that on soybean plant populations, row spacing, and soil conditions, can be useful to determine site suitability for a variety trial. The information could also be incorporated into statistical analysis to determine the number of replications needed to detect differences among varieties for their response to SCN.

Sugar beet nematode Heterodera schachtii distribution and harmfulness in Ukraine

Aim. To determine the distribution of sugar beet cyst nematode Heterodera schachtii in Ukraine, to defi ne its population density in soil, the degree of damage and the effi ciency of control measures. Methods. Field survey for soil samples, cyst extraction by fl otation and sieving method, light microscopy. Results. The examination of 12,130 ha of agricultural fi elds in six regions of Ukraine, conducted in 2010–2015, recorded the sugar beet cyst nematode to occur in fi ve of them (Kyiv, Chernihiv, Cherkasy, Khmelnytsky, and Vinnytsia), at a total area of 2,572 ha. Taking into consideration the results of previous nematological surveys, the presence of sugar beet cyst nematode has now been documented for 18 regions of Ukraine. In most regions H. schachtii was present in 10–11 % of the examined sugar and seed producing farms with nematode population densities reaching up to 142,000 eggs and juveniles in 100 cc of soil (710-fold above the economic threshold). Conclusions. The main reasons for this wide distribution of H. schachtii in Ukraine are seen in the negligence of prevention measures, unavailability of documented data on its occurrence (missing surveys), crop rotations with over 20 % of host plants, and unavailability of effi cient nematicides and domestic nematode-resistant sugar beet cultivars.

Effects of southern root knot nematode population densities and plant age on growth and yield parameters of cucumber

Southern root-knot nematode (Meloidogyne incognita) is one of the major constraints to cucumber production throughout the world. The effects of M. incognita on growth and yield of cucumber have not been studied. In the present studies, the effects of five initial population densities (500, 1000, 2000, 4000 and 8000 freshly hatched second stage juveniles) of M. incognita were investigated on growth and yield parameters of cucumber. The relationships between inoculum levels and growth and yield parameters at three plant ages were also determined. Cucumber plants of 2-, 3- and 4-week ages were inoculated with different nematode densities and observations were recorded 9 weeks after inoculation. Reductions in growth and yield parameters by nematode densities were calculated over control. All inoculum densities and ages of plants at the time of inoculation influenced growth and yield of cucumber. A positive correlation was found between inoculum levels and percent reductions in growth and yield parameters. On the other hand, ages of plants at inoculation had negative correlations with percent reductions in these parameters at each inoculum level. It is concluded that M. incognita has the potential to severely impair the growth of cucumber and delaying exposure of cucumber to nematodes can significantly abate yield losses.

Mixed Cropping System on Diversity and Density of Plant Parasitic Nematodes

<p>The potential of mixed cropping system on the diversity and suppression of nematodes was investigated at two locations in Ghana. The treatments in the study were; sole plantain, sole cassava and plantain+cassava systems replicated five and four times in a randomized complete block design (RCBD) at Kwadaso in the Ashanti and Assin Foso in the Central region of Ghana respectively. Growth parameters (height and girth) and components of yield (No. of suckers/plant, bunch weight/plant, No. of hands/plant, No. of fingers/plant) were studied on plantain in addition to No. of weevils per plant. On cassava, total biomass, tuber number and tuber weight (yield) were analyzed using GenStat software and means were separated with Fisher’s least significance test at a = 0.05. There were no differences in height and girth of plantain at Assin Foso. However, plant height was 25% and girth 13% more under sole plantain system over the mixed cropping system at Kwadaso. The sole plantain system recorded 60% and 75% more suckers than the Plantain-Cassava system at both locations. Mixed and sole cropping systems did not influence the diversity of nematode community but significant differences were observed in the density of the nematode taxa encountered under the two systems. Throughout the investigation at both locations, it was observed that the mixed cropping system recorded significantly (P < 0.05) lower nematode population densities in comparison to sole cropping system. It is therefore true that an agro-ecological strategy for pests and diseases control is the growing of a mixture of crops differing in their susceptibility to pests and pathogens</p>

Role of effective microorganisms in efficacy of Nemarioc-AG phytonematicide on suppression of Meloidogyne incognita and growth of tomato plants

ABSTRACTThe release of active ingredient chemicals in conventional organic amendments is primarily through microbial degradation, whereas in granular phytonematicides, leaching through irrigation water had been implied as a probable mechanism. The objective of this study was to determine the role of effective microorganisms (EM) on the efficacy of Nemarioc-AG (NAG; G = granular formulation) phytonematicide on suppression of root-knot (Meloidogyne species) nematodes and growth of tomato (Solanum lycopersicum) plants. A 5 × 6 factorial experiment, with EM at 0%, 0.14%, 0.17%, 0.20% and 0.25% and phytonematicide at 0, 3, 6, 9, 12 and 15 g per plant, was conducted under microplot conditions. Each plant was inoculated with 11,000 eggs and second-stage juveniles (J2) of Meloidogyne incognita. Seventy days after initiating the treatments, the interactions were not significant (P ≥ .05) on all variables, but the main factors were highly significant. Regression of nematode population densities, root gall and dry shoot mass over increasing phytonematicide concentration exhibited quadratic relations, which were explained by 93%, 97% and 99%, respectively. In contrast, stem diameter and phytonematicide concentration had a positive linear relation, which was explained by 98%. Nematode numbers over increasing EM concentration exhibited quadratic relation, which was explained by 97%. All plant variables and EM had no significant relations. In conclusion, the efficacy of NAG phytonematicide on nematode suppression and plant growth was independent of EM activities, suggesting that irrigation water played a major role in the efficacy of the product in granular formulation.