Helicotylenchus Pseudorobustus Research Articles

Relationship between soil factors with Helicotylenchus pseudorobustus isolated from tomato fields in Limpopo Province, South Africa

Helicotylenchus pseudorobustus is one of the tomato fields' most important plant-parasitic nematodes. In this study, the soil was sampled in 2023. The identification and determination of nematodes was made in the Aquaculture Research Unit at the University of Limpopo. During the investigation of this nematode in the Tzaneen region, the properties of soils infected with this nematode, including pH and EC, were investigated. The population of H. pseudorobustus was counted in 100 grams of soil in each season, and soil characteristics were also analysed at the same time. The results in different seasons of the year showed that the range of pH changes during the year of investigation was between 5.2 and 6.6, and the range of EC changes was between 2.9 and 4.3 mS. A comparison of EC and pH changes with population changes showed that the population increased approximately in the months when soil salinity decreased. In addition, soil structure (71.9% sand, 8.0% silt, and 20.1% clay) didn't influence the H. pseudorobustus population. However, the results showed no significant relationship between soil factors and the population dynamic of H. pseudorobustus nematode throughout the year.

Investigation on the population dynamics of Helicotylenchus pseudorobustus and its relationship with soil factors in tomato fields

Tomato (Solanum lycopersicum L.) is one of the premier vegetables in the world and is widely cultivated globally. As it is a relatively short-duration crop with a high yield, it is economically attractive, and the area under cultivation is increasing. Plant-parasitic nematodes are some of the most important plant pathogens in tomato farms. Helicotylenchus pseudorobustus is one of the most important plant-parasitic nematodes in tomato fields. Therefore, understanding the population dynamics of H. pseudorobustus on the tomato field assists the farmer in managing them and having better yields. In this study, the soil was sampled in 2022. Identification and determination of nematodes were made in the Aquaculture Research Unit, University of Limpopo. The properties of soils infected with this nematode, including pH and EC, were investigated during the investigation of this nematode in the Dalmatia region. The population of H. pseudorobustus was counted in 100 grams of soil in each season, and soil characteristics were also analyzed at the same time. The results in different seasons of the year showed that the range of pH changes during the years of investigation was between 7.5 and 7.7, and the range of EC changes was between 1.3 and 2.0 dS/m. A comparison of EC and pH changes with population changes showed that the population increased approximately in the months when soil salinity decreased. In addition, as the pH increases, the population of H. pseudorobustus also increases. However, no significant relationship was found between the values of pH, EC, and changes in the population of H. pseudorobustus nematode throughout the year.

EFFECT OF PLANT BASED NEMATICIDE ON POPULATION OF PARASITIC NEMATODES AND BACTERIA ASSOCIATED WITH OKRA (ABELMOSCHUS ESCULENTUS L. MOENCH)

Rapid declines in nematode populations has been observed by the use of organic amendments in soil when decomposing plant based material release toxic compounds, while long term effects include increase in the yield and have no toxic effect on soil bacteria unlike the chemicals. In the present experiment Turtob-F was used to control population of three plant nematodes and to observe its effect on yield and population of Klebsiella sp. in soil. The population of all three nematode namely Meloidogyne incognita, Helicotylenchus pseudorobustus and Tylenchorhynchus indicus were remarkably decreased (P<0.001) by Turtob-F. The yield of okra was significantly increased (P<0.01) by the application of Turtob-F, whereas the population of bacterial sp. Klebsiella remains unchanged during the experiment.

Parasitic Nematodes of Plant Persimmon (Diospyros Kaki, l.) Rhizosphere in District Swat, Kp Pakistan

Purpose: Different species of plant parasitic nematodes of persimmon (Diospyros kaki, L.) were identified from various localities of District Swat KPK Pakistan namely Chail, Madyan, Piya, Jare, Chikrai, Thesil, Fateh pur, Baghdheri, Naway kalay, Shin, Pirpatay, Sambat and Gurra. Methods: Soil samples were collected from the bases of persimmon trees along with rhizospheres that show stunted growth. The collected samples were then processed by using modified Bearmann funnel technique. Nematode specimens isolated in cavity block were killed by heat and treated with TAF (Triethylamine formaldehyde) solution. Findings and Practical implication: After 24 hours, the specimens were transferred to 1.25 % glycerin with trace amount of picric acid for staining of nematodes. Nine different species of nematodes were reported from these localities were Tylenchus spp, Psilenchus spp, Meloidogyne larvae, Aphelenchus spp, Tylenchus juveniles, Filenchus spp, Pratylenchus spp, Helicotylenchus pseudorobustus and Helicotylenchus dihystera. Helicotylenchus species were more common in the collected samples. Conclusion: It is concluded from analysis of soil samples that plant parasitic nematodes associated with persimmon cause economic loss in district swat. Persimmon plants show stunted and retarded growth in soil which has high nematode population density. Keywords: Nematodes, Persimmon, Swat, Diospyros kaki, Triethylamine formaldehyde.

Organic amendments as an ecofriendly substitute of carbofuran for the suppression of nematodes associated with Malus pumila

• Carbofuran and cow dung were applied to soil against nematodes. • Carbofuran killed maximum nematodes in 3 months but it is toxic. • Cow dung gave similar results in 6 months. • Cow dung is an ecofriendly option for the protection of plants against nematodes. Plant-parasitic nematodes infect the roots of crops which bring rigorous economic loss to food industry across the globe. Several plant protection agents are being used but they cause severe negative environmental and health impacts. Recently, organic matter has become an important green alternative for several pesticides including nematicides. In the present study, identification and management of stylet bearing nematodes associated with Malus pumila from different locations of Khanpur, Pakistan, have been presented. Soil samples were collected from the rhizosphere of infected M. pumila and isolated using Baermann funnel extraction technique. Collected specimens were killed, fixed and mounted. After identification, cow dung (organic) and carbofuran (inorganic) were applied after taking the first soil samples and soil samples were recollected and analyzed after 3 months of applications. Ten species of nematodes; Helicotylenchus pseudorobustus, Helicotylenchus dihystera, Helicotylenchus vulgaris, Meloidogyne javanica, Meloidogyne incognita, Aphelenchus avenae, Pratylenchus penetrans, Filenchus sheri, Psilenchus hilarulus and Tylenchus semipenetrans were identified from different locations. Results of amendments revealed that carbofuran was found more effective because of its intense toxic properties, whereas nematode decline rate was slow in case of organic amendments. Being an insecticide, carbofuran killed maximum nematodes but it is highly toxic. If the time period is increased, comparable results can be achieved by applying cow dung, which makes it an environmentally friendly option for the protection of plants against nematodes.

Harmonics, evolutionary generators, DANCE, and HEAR-functional dimensions.

Evolution of the major kingdoms of life has spanned over the last 4 billion years on Earth. Studies of the process comprise different fields of study with alternative perspectives. This paper focuses on mathematic unification of the subject area; enriching an engineering based structure to advance our understanding of pathways which lead to distinct constructs in life, furthering geographic bordering processes with biological context. Application of logistic regression requires partitioning of variance within cellular and molecular systems; use of higher mathematic technique (multi-objective genetic algorithm) generates variance within the different scales of evolution, the result of which is analogous with the Fisher equation model of gene distribution within populations. Laboratory and field studies were integrated to illustrate emergence in evolutionary processes in the terrestrial/soil environment. Nematological field and laboratory trials validate the existence of triangular relationships within biological communities; further harmonic constants between interacting species may be found with emergent consequence. We distinguish different strategical groupings in the soil community, with the core groupings recognized with Meloidogyne spp. illustrating positive (emergent) growth; Radopholus similis (neutral growth), and Helicotylenchus pseudorobustus (negative growth). The patterns of emergent systems are shown in the extremes of Morocco's dynamic soil environment. Fuzzy classification methods: Mamdani, Takugi-Sugeno-Kang; additional novel DANCE (Differential Algorithmic Network Centered Emergence) and functional expressions HEAR (Harmonic Evolutionary Algorithmic Resilience), are recommended to give a basis for development of constructs covering different categories of life.

Phytonematodaphauna Of Vegetable Crops And Anti-Parasitic Measures In The Greenhouse Conditions Of The Surkhandarya Region

This article covers phytonematodaphauna of vegetable crops and measures against parasites in the greenhouse conditions of the Surkhandarya region. The phytonematodes found and identified as a result of the research carried out belong to 5 categories, 18 families, 32 generations, 68 species according to taxonomic classification. Studies 15 species of true parasite fetonimatoda in the soil around the tomato plant and its roots in the greenhouse conditions of the Surkhandarya region (Bitylenchusdubius, Merliniines brevidens, Tylenchorhynchus brassicae, Rotylenchus robustus, Helicotylenchus pseudorobustus, H. digonicus, H. Dihystera, H. digitiformis,H.erythrinae, Pratylenchus pratensis, P.penetrans, Meloidogyne incognita, M. javanica, M. arenaria, Ditylenehus dipsaci) the prevalence was determined.

Molecular and morphological characters of Helicotylenchus Steiner, 1945 species from Iran with a note on the identity of H. pseudorobustus (Steiner, 1914) Golden, 1956.

Helicotylenchus species were recovered from natural areas of three provinces (Mazandaran, Kerman and Guilan) in Iran, with morphological and molecular characteristics suggesting that they were Helicotylenchus minzi and Helicotylenchus pseudorobustus. A phylogenetic analysis of the two Helicotylenchus species using 28S rDNA placed H. pseudrobustus and H. minzi in a clade with 1.00 posterior probability. Results suggest that the Helicotylenchus population identified using molecular characteristics as H. pseudorobustus is a paraphyletic group, with hierarchical clustering analysis indicating a close relationship between the Iranian and the Chinese populations of H. pseudorobustus. In conclusion, further molecular studies within the genus Helicotylenchus are needed, especially for morphologically similar populations that have been recognized as separate species.

Diversity and seasonal fluctuation of tylenchid plant-parasitic nematodes in association with alfalfa in the Kerman Province (Iran)

Abstract The diversity and seasonal fluctuations of plant-parasitic nematodes (tylenchids) were investigated in five alfalfa fields in five counties of the Kerman Province of Iran during four consecutive seasons in 2013. Hundred soil samples were obtained per county, with 25 sub-samples per field being composited to five to represent five replicates per field per county per season. In total, 500 samples were analyzed during the study. Nematodes were extracted from soil samples using the modified tray method. In total, 11 plant-parasitic nematode genera and 12 species were recorded. According to prominence values, Ditylenchus (e.g. D. acutus, D. myceliophagus, D. terricolus and D. sarvarae), followed by Helicotylenchus pseudorobustsus, Pratylenchus neglectus and Meloidogyne javanica were the most prominent species. The season and the localities significantly affect the population densities of nematodes. Values for both the Shannon (H’) and Evenness (E) indices were the highest in Bam and the lowest in Jiroft counties. A significant, negative correlation existed between soil pH and mean population densities of Scutylenchus rugosus, while significant and positive correlations existed between soil electrical conductivity and Helicotylenchus pseudorobustus, Aphelenchoides sp., Amplimerlinius globigerus and Pratylenchus neglectus. In conclusion, diversity of plant-parasitic nematodes in Bam county was higher than other localities.

Morphological and molecular characterization of three Helicotylenchus species from Iran

Three Helicotylenchus species, namely Helicotylenchus digonicus, Helicotylenchus pseudorobustus and Helicotylenchus vulgaris were identified during a nematode survey conducted in Iran. The morphological and molecular characteristics of the species were defined. In addition, phylogenetic analysis of five Iranian Helicotylenchus populations based on 28S rDNA were done and showed the unresolved position of molecularly identified H. pseudorobustus and H. digonicus. However, populations of H. vulgaris and H. digonicus were placed close to each other. Phylogenetic analysis confirmed that molecularly characterized Helicotylenchus species formed a monophyletic clade. A detailed revision of the species is, however, needed. Illustrations and measurements for all species are provided.

Interspecific differences in nematode control between range-expanding plant species and their congeneric natives

Climate change enables range expansions of plants, animals and microbes to higher altitudes and latitudes. Plants may benefit from range expansion when they escape from natural enemies. However, range expansion becomes a disadvantage when plants become disconnected from organisms that control enemies in the new range. Here, we examined nematode control in the root zone of range-expanding plant species and congeneric natives. In a greenhouse, we determined bottom-up (by the plants) and top-down (by natural enemies of the nematodes) control of two root-feeding nematode species (Helicotylenchus pseudorobustus and Meloidogyne hapla) in the rhizospheres of two range-expanding plant species, Centaurea stoebe and Geranium pyrenaicum, and two congeneric natives, Centaurea jacea and Geranium molle. Pots with plants growing in sterilized soil were inoculated with either a microbial soil community from the newly colonized natural habitat, a mixture of native microbial nematode antagonists, or a combination of these two communities. We tested the hypotheses that bottom-up control of root-feeding nematodes would be strongest in the root zone of range expanders and that top-down control would be strongest in the root zone of native plant species. We observed profound intra- and interspecific differences in bottom-up and top-down control among all four plant species. Bottom-up control by the range-expanding plant species was either strong or weak. Top-down control by microbes was strongest in native Centaurea. The addition of a mixture of both microbial communities reduced control of M. hapla in the root zones of the native plant species, and enhanced its control in the root zones of range-expanding plant species. We conclude that there was species-specific bottom-up and top-down control of root-feeding nematodes among the four plant species tested. Range-expanding plant species influenced their microbial rhizosphere community differently compared to native plant species, but top-down control in the root zone of natives was not systematically superior to that of range-shifting plant species.

Spiral Nematode, Helicotylenchus pseudorobustus (Steiner, 1941) Golden, 1956 (Nematoda: Tylenchida: Hoplolaimidae)

Spiral nematodes of the genus Helicotylenchus are among the most ubiquitous plant-parasitic nematodes worldwide. Helicotylenchus pseudorobustus is a species common in Florida and the southeastern United States and is frequently found associated with turfgrasses and other grass hosts in the region. On most plants, it is not considered particularly damaging, but recent research has shown that this species suppresses growth of certain turfgrass hosts. Seashore paspalum, a turfgrass used in tropical and subtropical regions, is particularly susceptible to infestation. This 4-page fact sheet was written by William T. Crow and published by the UF Department of Entomology and Nematology, January 2013.
 http://edis.ifas.ufl.edu/in973

Host location success of root-feeding nematodes in patches that differ in size and quality: A belowground release-recapture experiment

Resource patch size and patch nutritional quality are both important factors influencing local densities of herbivores. The responses of herbivores to resource patch size have been mostly studied in aboveground plant–insect interactions, whereas belowground organisms have received little attention. We studied responses of different root-feeding nematode species associated with marram grass (Ammophila arenaria (L.) Link) to resource patch size and quality. Different nematode species were released in experimental mesocosms filled with dune sand in which we established marram grass patches of varying sizes. Half of the patches of small, medium and large size were fertilized to test if immigration probabilities of nematodes depended on patch quality. We tested the hypotheses that (1) nematodes should aggregate on larger patches and (2) colonization of patches would also depend on patch nutritional quality, with higher nematode recapture rates expected in fertilized patches. Two species (Helicotylenchus pseudorobustus, Hemicycliophora thornei) of the five released species were recaptured in the experiment. The fraction of nematodes immigrating into the rhizosphere of a plant patch increased with patch size (i.e. root biomass), which was in line with predictions of the Resource Concentration Hypothesis. When fractions were recalculated to represent recapture rates per liter of soil, recapture rates of nematodes did not differ among patch sizes, indicating that the increase in recapture rates was directly proportional to the increase in patch size. This suggests that the process through which nematodes located patches was not distinguishable from a random process where entering patches is based on random encounters with patch boundaries. In contrast to our expectation, fertilization had a strong negative effect on patch responses of both nematode species. Our study represents an approach that may be used to explore whether belowground biota behave in similar ways as aboveground biota, in order to determine how perceived differences in environments affect ecological interactions.

Plant-Parasitic Nematodes Are Potential Pathogens of Miscanthus × giganteus and Panicum virgatum Used for Biofuels.

A survey of Miscanthus × giganteus and switchgrass plots throughout the midwestern and southeastern United States was conducted to determine the occurrence and distribution of plant-parasitic nematodes associated with these biofuel crops. During 2008, rhizosphere soil samples were collected from 24 Miscanthus × giganteus and 38 switchgrass plots in South Dakota, Iowa, and Illinois. Additional samples were collected from 11 Miscanthus × giganteus and 10 switchgrass plots in Illinois, Kentucky, Georgia, and Tennessee the following year. The 11 dominant genera recovered from the samples were Pratylenchus, Helicotylenchus, Xiphinema, Longidorus, Heterodera, Hoplolaimus, Tylenchorhynchus, Criconemella, Paratrichodorus, Hemicriconemoides, and Paratylenchus. Populations of Helicotylenchus, Xiphinema, and Pratylenchus were common and recorded in 90.5, 83.8, and 91.9% of the soil samples from Miscanthus × giganteus, respectively, and in 91.6, 75, and 83.3% of the soil samples from switchgrass, respectively. Prominence value (PV) (PV = population density × √frequency of occurrence/10) was calculated for the nematodes identified. Helicotylenchus had the highest PV (PV = 384) and was followed by Xiphinema (PV = 152) and Pratylenchus (PV = 72). Several of the nematode species associated with the two biofuels crops were plant parasites. Of these, Pratylenchus penetrans, P. scribneri, P. crenatus, Helicotylenchus pseudorobustus, Hoplolaimus galeatus, X. americanum, and X. rivesi are potentially the most damaging pests to Miscanthus × giganteus and switchgrass. Due to a lack of information, the damaging population thresholds of plant-parasitic nematodes to Miscanthus × giganteus and switchgrass are currently unknown. However, damage threshold value ranges have been reported for other monocotyledon hosts. If these damage threshold value ranges are any indication of the population densities required to impact Miscanthus × giganteus and switchgrass, then every state surveyed has potential for yield losses due to plant-parasitic nematodes. Specifically, Helicotylenchus, Xiphinema, Pratylenchus, Hoplolaimus, Tylenchorhynchus, Criconemella, and Longidorus spp. were all found to have population densities within or above the threshold value ranges reported for other monocotyledon hosts.

Diversity and incidence of plant-parasitic nematodes in Belgian turf grass

Abstract Eleven golf courses and eight football pitches, located in Belgium, were surveyed for plant-parasitic nematodes. This revealed a remarkably high diversity: 52 different species/taxa were identified morphologically, belonging to 23 genera and nine families. Among the most prevalent nematodes on both sports field types were Helicotylenchus pseudorobustus and Meloidogyne naasi (>85% and >45% of the analysed samples, respectively). Golf greens contained a higher density and diversity of cyst nematodes than football fields. Cyst nematode species included Punctodera punctata, Heterodera mani, H. ustinovi, H. bifenestra and H. hordecalis. Multivariate statistics of the first three species showed that they could be separated based on morphometrical characters of juveniles, but not on values based on the vulval pattern. Several detected species, e. g., Meloidogyne minor, are a potential source of infestation of agricultural fields. This study shows the importance of plant-parasitic nematodes in turf grass in temperate Europe. In addition, a comparison between two extraction methods revealed that significantly more nematodes were extracted with the zonal centrifuge than after 2 weeks extraction with the Baermann method, except for juveniles of Meloidogyne spp. and cyst-forming species.

THE INFLUENCE OF MINERAL FERTILIZER APPLICATION AND PLANT NUTRITION ON PLANT-PARASITIC NEMATODES IN UPLAND AND LOWLAND RICE IN CÔTE D'IVOIRE AND ITS IMPLICATIONS IN LONG TERM AGRICULTURAL RESEARCH TRIALS

Mineral fertilizer application and consequent plant nutrition has long been observed to influence associated plant-parasitic nematode population densities, offering the potential as a nematode management option. Observations were made on the influence of mineral fertilizer application on nematode populations on three separate long-term rice experiments, (differential mineral application on upland and on lowland rice, and P application on upland rice) undertaken between 1994 and 1997 in Côte d'Ivoire. In 1995, on upland rice, treatments with K or N withheld from the comprehensive mineral application treatment (range of elements including N, P, K, Ca, Mg and Zn) led to lower densities of Pratylenchus zeae at harvest than the comprehensive mineral application. By withholding K or Mg, Helicotylenchus pseudorobustus densities were greater than with either the control (no mineral application) or comprehensive mineral application in the same year. No differences were observed between treatments in 1994, or between treatments for densities of other nematode species present (Meloidogyne incognita, Criconemella tescorum) or for total nematode density. In the lowland rice trial, no treatment effects on nematode species (Hirschmanniella oryzae and Uliginotylenchus palustris) were observed. In the P application trial on a P-deficient Ultisol, Heterodera sacchari densities were lower in treatments receiving 180 kg P ha−1, than untreated in 1995; in 1996 no differences were observed between untreated and 135 kg P ha−1, while in 1997 higher densities of H. sacchari were present in 135 kg P ha−1 than untreated. Regression analysis of nematode densities against the mineral straw content in the P application trial revealed a negative correlation between M. incognita and Mn and Ca, and between P. zeae and Zn or Fe. A positive correlation was observed between Helicotylenchus spp. and Mg. This study provides strong arguments for taking plant parasitic nematodes into account when planning and executing long-term research trials.

The potential of mixed covers of Sesbania, Tephrosia and Crotalaria to minimise nematode problems on subsequent crops

Root-knot nematodes ( Meloidogyne javanica) associated with Sesbania sesban and Tephrosia vogelii and root-lesion nematodes ( Pratylenchus spp.) associated with Crotalaria grahamiana limit the effectiveness of these leguminous cover crops for replenishing soil fertility. As Crotalaria spp. are antagonistic to Meloidogyne, and S. sesban and T. vogelii suppress Pratylenchus, a field study was conducted on farms in western Kenya to test whether mixing S. sesban or T. vogelii with C. grahamiana can resolve the nematode problems associated with pure crops of the respective species. The pure and two-species mixed cover crops, grown for 10 or 12 months, were evaluated against natural and bare fallows. Maize ( Zea mays) and bean ( Phaseolus vulgaris) were then intercropped and the plots split to determine the effects of incorporating the biomass of natural fallows/cover crops against its removal on nematode infection of crops. T. vogelii and S. sesban were highly infected by Meloidogyne and their pure crops supported increased populations of this nematode. In mixed systems, C. grahamiana did not affect Meloidogyne infection of S. sesban and T. vogelii, but it significantly reduced the soil nematode populations compared with the respective pure crops. Root-lesion ( Pratylenchus zeae, P. thornei and P. pseudopratensis) and spiral nematodes ( Helicotylenchus pseudorobustus and Scutellonema brachyurus) were greatest in number following pure C. grahamiana. Mixing C. grahamiana with either S. sesban or T. vogelii did not restrict these nematode populations. Meloidogyne infection of bean following S. sesban+C. grahamiana and T. vogelii+C. grahamiana was restricted and the crop after these mixed systems did not lose yield compared with that after pure S. sesban and T. vogelii. All cover crops, except pure C. grahamiana and its mixture with S. sesban at Yala, increased maize yields compared with natural and bare fallows. In situ decomposition of the foliar biomass of cover crops and natural fallow did not affect nematode infection of both the annual crops. The Meloidogyne problem associated with S. sesban and T. vogelii covers on subsequent annual crops such as bean can be limited by mixing either of these shrubs with C. grahamiana.

Plant-parasitic nematodes in field crops in South Africa. 6. Soybean

AbstractTwelve plant-parasitic nematode genera and 25 species were identified in soil and root samples collected from 17 localities in the soybean production areas of South Africa during the 1995/96 season. Predominant endoparasites found included Meloidogyne incognita, M. javanica, M. hapla, M. ethiopica, Pratylenchus zeae and P. brachyurus. Meloidogyne species occurred in 91% of all root samples, P. zeae in 87% and P. brachyurus in 33%. The occurrence of the three predominant endoparasites was not restricted to sandy soil, but they were also prevalent in soils with high clay contents. Other endoparasitic nematode species were Pratylenchus crenatus, P. teres, P. neglectus, P. thornei, Rotylenchulus parvus and Ditylenchus africanus. Nematodes found in soil included Helicotylenchus dihystera and Scutellonema brachyurus, which occurred in 78 and 71%, respectively, of all soil samples. Other nematodes found in soil samples were Helicotylenchus pseudorobustus, H. digonicus, H. microcephalus, Scutellonema truncatum, Rotylenchus unisexus, Mesocriconema sphaerocephalum, Paratrichodorus minor, Longidorus pisi, Xiphinema vanderlindei, X. elongatum and Tylenchorhynchus goffarti. Highest prominence values (PV) for Meloidogyne species were recorded on cultivars Prima, Bakgat, Tamboti, Hutcheson and Knap and the lowest on cultivars PAN812, SCS1, Nyala, Gazelle and A7119. Eight nematode genera and 19 species extracted during this study are reported for the first time in association with soybean in South Africa.

Seasonal dynamics and vertical distribution of plant-feeding nematode communities in grasslands

The vertical distribution and seasonal dynamics of plant- and fungal-feeding nematode taxa in permanent grasslands were investigated. Dolichodoridae, Paratylenchus, Pratylenchus, Tylenchidae and Aphelenchoidesdominated the upper 10 cm soil and their numbers strongly decreased with depth. The vertical distribution of these nematodes was correlated with the distribution of roots in the soil profile. Longidorus elongatus, Helicotylenchus pseudorobustus and Aphelenchus avenae were, however, also prevalent in the deeper soil layers. Trichodoridae and Hemicycliophora thornei seemed to prefer a depth of 30–40 cm. Most of the plant-feeding nematode taxa had an annual cycle in their abundance and population structures, which could largely be related to seasonal changes in the temperature and moisture contents of the soil. Although adult stages of sedentary endoparasitic genera were not counted, the peak number of juvenile Heteroderaand Subanguinanematodes in spring indicated a distinct annual population cycle for these genera. The lowest densities of the semi-endoparasite Helicotylenchus pseudorobustus and the ectoparasites Geocenamus nanus, Tylenchorhynchus dubius, Paratylenchus nanus, Paratylenchus veruculatus and, to a lesser extent, Tylenchorhynchus maximus were found in winter/early spring, but their densities increased in summer/autumn. Generally, the population growth of these species in summer was preceded by a large proportion of adults followed by an increased number of juveniles. Taxa with short life cycles that could produce more generations per year, such as Tylenchidae and Aphelenchidae, and taxa with generation times of more than a year, such as Longidorus elongatus, generally did not show a distinct annual cycle.

Occurrence, Spatial Distribution, and Pathogenicity of Some Phytoparasitic Nematodes on Creeping Bentgrass Putting Greens in Kansas

Eleven genera of phytoparasitic nematodes, of which Criconemella, Helicotylenchus, Tylenchorynchus and Hoplolaimus were the most abundant, were recovered from soil samples collected from 81 creeping bentgrass (Agrostis palustris Pencross') putting greens in Kansas. The relationship between population densities of Criconemella ornata, Helicotylenchus pseudorobustus, and Hoplolaimus galeatus and growth and quality of turfgrass was studied in detail(.)