Abundance and trophic structure of pine forest nematodes in relation to soil layers and ground cover

In a 15-20 yr old forest of Scots pine, the total number of nematodes under the dominating cover grass Deschampsia flexuosa , reached 4.0–4.7 × 10⁶ ind. m⁻² stone free soil, corresponding to densities of 8770–9090 and 3500–3790 ind. 100 ml⁻¹ in FH and mineral soil, respectively. Root/fungal feeding nematodes formed 53–59% of the total nematode fauna. The majority in this group was potential mycophages. Obligate root feeders formed only 11–17% of the total number of nematodes. Soil layers and ground cover affected the abundance of trophic groups. Bacterial feeders, potential mycophages and miscellaneous feeders reached their maximal abundance in the FH-layer. Obligate root feeders tended to reach higher densities in the mineral soil. Higher abundance values of most trophic groups were found under forest grass. The species Calamagrostis arundinacea had a striking positive effect on the relative and absolute abundance of obligate root feeders. This group may be most numerous in early stages of forest development.     

Plant parasitic nematodes associated with ornamental plant Pseuderanthemum atropurpureum in Aligarh district of western Uttar Pradesh

A survey was conducted to determine the nematodes associated with the soil, substratum and roots of the ornamental plant, Pseuderanthemum atropurpureum, grown in the Aligarh district of western Uttar Pradesh, India. Ten genera of plant parasitic nematodes, viz. Meloidogyne spp., Helicotylenchus sp., Hemicriconemoides sp., Hoplolaimus sp., Xiphinema sp., Pratylenchus sp., Trichodorus sp., Tylenchorhynchus sp., Aphelenchoides sp. and Rotylenchus sp., were isolated from 345 soil samples collected from 15 different localities. Our study indicates that among the 10 genera of the plant parasitic nematodes, Meloidogyne spp. was widely spread in all the examined localities of Aligarh district, except at Khair. It was observed that the population density and diversity of nematodes in all the soil samples was not uniform. Meloidogyne spp. showed the highest absolute frequency and relative frequency followed by Helicotylenchus sp., Hemicriconemoides sp., Xiphinema sp., Hoplolaimus sp., Pratylenchus sp., Trichodorus sp., Tylenchorhynchus sp., Aphelenchoides sp. and Rotylenchus sp. Since no records are available in the literature related to the association of root-knot nematode in P. atropurpureum, it is worthy to note that this study may be considered as a new hope towards further study of the interaction between the root-knot nematode and ornamental plant P. atropurpureum if any.     

Migratory plant parasitic nematodes as pests of cereals

Two field trials showed that initial populations of Tylenchus Bastian, Paratylenchus Micoletzky, Pratylenchus minyus Sher and Allen, P. crenatus Loof, P. penetrans Chitwood and Oteifa, Helicotylenchus pseudorobustus Golden and H. digonicus Perry did not decrease yield of cereals whereas a significant inverse relationship existed between populations of Tylenchorhynchus dubius Filipjev and yield of wheat. T. dubius and Longidorus spp. Filipjev were associated with early leaf-yellowing of barley, though difficulty in controlling nematodes failed to firmly link yield reduction with nematode populations. The possible variability in tolerance of cereals to nematodes is discussed.     

Spatial Distribution of Plant-Parasitic Nematodes in Semi-Arid Vitis vinifera Vineyards in Washington

The most commonly encountered plant-parasitic nematodes in eastern Washington Vitis vinifera vineyards are Meloidogyne hapla, Mesocriconema xenoplax, Pratylenchus spp., Xiphinema americanum, and Paratylenchus sp.; however, little is known about their distribution in the soil profile. The vertical and horizontal spatial distribution of plant-parasitic nematodes was determined in two Washington V. vinifera vineyards. Others variables measured in these vineyards included soil moisture content, fine root biomass, and root colonization by arbuscular mycorhizal fungi (AMF). Meloidogyne hapla and M. xenoplax were aggregated under irrigation emitters within the vine row and decreased with soil depth. Conversely, Pratylenchus spp. populations were primarily concentrated in vineyard alleyways and decreased with depth. Paratylenchus sp. and X. americanum were randomly distributed within the vineyards. Soil water content played a dominant role in the distribution of fine roots and plant-parasitic nematodes. Colonization of fine roots by AMF decreased directly under irrigation emitters; in addition, galled roots had lower levels of AMF colonization compared with healthy roots. These findings will help facilitate sampling and management decisions for plant-parasitic nematodes in Washington semi-arid vineyards.     

Nematodes associated with forest and woodland trees in Scotland

A survey of the nematode genera associated with trees in Scotland showed that Tylenchus sensu lato, Aphelenchoides, Tylencholaimus, Trichodorus, Helicotylenchus, Rotylenchus, Criconemoides s.l., Hemicriconemoides, Tylencho-rhynchus, Pratylenchus and Paratylenchus s.l. were commonly found in soil samples collected from around the roots of coniferous and deciduous trees. Only Criconemoides s.l. appeared to have a significant preference for deciduous woods. The presence of undergrowth in woods and forests was associated with significantly greater numbers of plant-parasitic nematodes. Measurements of abiotic factors indicated that, in mineral soils, pH affected the incidence of most genera, but soil type, moisture content and altitude had little effect.     

Occurrence and correlations of nematodes,Fusarium oxysporum and edaphic factors on banana plantations

Problems caused by nematodes and Fusarium wilt (Panama disease) on banana plantations are responsible for yield losses and are limiting to its cultivation. In the state of Goias, there is little information about the nematode occurence on this crop, and its relation with the incidence of Fusarium oxysporum f.sp. cubense (Foc). This research had the purpose to identify the occurrence of plant‐parasitic nematodes on banana plantations and to verify its correlation with the Fusarium wilt and with the soil attributes (pH, texture, nutrients). Twelve banana orchards in the state of Goias were sampled in the municipalities of Anapolis, Caiaponia, Goiatuba, Itaguaru, Itumbiara (two areas), Jatai, Morrinhos, Ouro Verde, Palestina, Taquaral and Uruana. All sampled areas, except Morrinhos, revealed contamination with Foc, and all areas had different genera of nematodes either in the soil or in the roots samples. Meloidogyne sp., Helicotylenchus sp. and Rotylenchus sp. were the main genera of plant‐parasitic nematodes found in the samples, with Meloidogyne sp. and Rotylenchus sp. being the most dominant and abundant genera. The presence of Pratylenchus sp. increases the population levels of F. oxysporum. Helicotylenchus sp. is highly correlated with high concentrations of Mn. High population density of Meloidogyne sp. was found in irrigated areas with low concentrations of P, Ca, Mg and soil pH.     

The effect of red wood ant abundance on feeding damage by the pine weevil Hylobius abietis

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Effects on vegetation composition of a modified forest harvesting and propagation method compared with clear‐cutting,scarification and planting

Question: How does the vegetation of boreal forests respond to harvesting and scarification? Location: 650 m a.s.l., central Sweden (61°38’ N). Methods: The response of boreal forest vegetation to cutting and scarification was studied in a field trial, which consisted of three treatments plus conventional harvesting as a control in a complete block design with four replicates. The cutting was done 14 years prior to vegetation inventory and scarification and planting were conducted the first or second years after cutting. Results: The species most abundant at higher cutting intensities were crustose lichens, Cladonia spp., Cladina arbuscula, Polytrichum spp. and pioneer mosses, the grass Deschampsia flexuosa, and the tree Betula pubescens, A few species had substantially lower abundance in treatments with higher cutting intensity, notably Hylocomium splendens and Vaccinium myrtillus. Scarification had a strong effect that was different from the one created by cutting. In scarification treatments, Polytrichum spp. were the only species with high abundance; most species had low abundance, i.e. Barbilophozia lycopodioides, Vaccinium vitis‐idaea, Pleurozium schreberi, Carex globularis, Empetrum nigrum, Cladina arbuscula, Sphagnum spp. Conclusions: Our results elaborate on the details of the well‐known effect of cutting on ground‐layer flora, and also give support for the profound and long‐lasting effect that soil scarification has on forest vegetation.     

Nematodes in Scottish forest nurseries

Seven hundred soil samples from 41 forest nurseries were collected between 1972 and 1975 and examined for plant parasitic and predatory nematodes. Rotylenchus goodeyi, Trichodorus primitivus, Cephalenchus emarginatus and Tylenchus davainei occurred in most nurseries but their numbers were generally lower than those of R. robustus and Paratrichodorus pachydermus. In a glasshouse experiment as few as 10 R. robustus decreased the growth of Sitka spruce seedlings. It was estimated that Rotylenchus and trichodorid nematodes probably retarded the growth of some seedling trees in eight of the nurseries sampled. During the survey, Trichodorus sparsus was found for the first time in Great Britain and Paralongidorus maximus for only the third time. Since both these species were found in nurseries they were probably introduced and are ideally situated to be more widely disseminated.     

Neighboring Deschampsia flexuosa and Trientalis europaea harbor contrasting root fungal endophytic communities

Fungal endophytic communities and potential host preference of root-inhabiting fungi of boreal forest understory plants are poorly known. The objective of this study was to find out whether two neighboring plant species, Deschampsia flexuosa (Poaceae) and Trientalis europaea (Primulaceae), share similar root fungal endophytic communities and whether the communities differ between two sites. The study was carried out by analysis of pure culture isolates and root fungal colonization percentages. A total of 84 isolates from D. flexuosa and 27 isolates from T. europaea were obtained. The roots of D. flexuosa harbored 16 different isolate types based on macromorphological characteristics, whereas only 4 isolate types were found in T. europaea. The root colonization by dark septate and hyaline septate hyphae correlated with isolate numbers being higher in D. flexuosa compared to T. europaea. The different isolate types were further identified on the basis of internal transcribed spacer sequence and phylogenetic analysis. An isolate type identified as dark septate endophyte Phialocephala fortinii colonized 50 % of the T. europaea and 21 % of the D. flexuosa specimens. In addition, Meliniomyces variabilis, Phialocephala sphaeroides, and Umbelopsis isabellina were found colonizing the grass, D. flexuosa, for the first time and Mycena sp. was confirmed as an endophyte of D. flexuosa. Site-specific differences were observed in the abundance and diversity of endophytic fungi in the roots of both study plants, but the differences were not as predominant as those between plant species. It is concluded that D. flexuosa harbors both higher amount and more diverse community of endophytic fungi in its roots compared to T. europaea.     

Maturation feeding and transmission of Bursaphelenchus xylophilus (Nematoda: Parasitaphelenchidae) by Monochamus alternatus (Coleoptera: Cerambycidae) inoculated with Beauveria bassiana (Deuteromycotina: Hyphomycetes)

We examined the amount of maturation feeding and transmission of pinewood nematodes, Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle (Nematoda: Parasitaphelenchidae), to healthy pine (Pinus spp.) trees by pine sawyer Monochamus alternatus Hope (Coleoptera: Cerambycidae) adults infected with Beauveria bassiana (Balsamo) Vuill. (Deuteromycotina: Hyphomycetes). Inoculated beetles fed less than noninoculated beetles, probably because feeding by inoculated beetles began to decrease at about 4 d postinoculation and inoculated beetles ceased to feed for several days before their death. In inoculated beetles carrying >1,000 nematodes, some beetles died before nematode departure. The remaining heavily nematode-infested beetles lived until the beginning of nematode departure, but they had stopped feeding, preventing the nematodes from entering pine twigs. We suggest that microbial control of pine sawyer adults by B. bassiana may be effective in preventing transmission of pine wilt disease to healthy pine trees.     

A thorough study of a Paratylenchus sp. in glasshouse‐grown lettuce: Characterisation,population dynamics,host plants and damage threshold as keys to its integrated management

In glasshouses practising monoculture of butterhead lettuce in Belgium, high densities of pin nematodes (Paratylenchus spp.) are frequently associated with reduced plant growth. Growers currently apply chemical soil disinfestation measures to manage this problem, although stricter phytosanitary regulations are forcing a shift towards integrated management. Efficient implementation of such management requires knowledge about the factors influencing nematode population dynamics, and the damage threshold for lettuce. The nematode populations in five Belgian glasshouses were monitored for at least 1 year by frequently soil sampling at 0–30 cm and 30–60 cm depth. An undescribed species of Paratylenchus was identified in all glasshouses based on morphological and molecular features. High nematode densities (>20,000 (100 ml soil)^?1) occurred in winter and spring. Chemical soil disinfestation lowered these populations greatly, although up to 14% survived in the deeper soil layer. After soil steaming under negative pressure, no pin nematodes were found. After 2 months of black fallow pin nematode densities were reduced by 50%–76%. Lamb's lettuce, parsley and wild rocket were found to be poor hosts in a pot experiment, while reproduction factors (P_f/P_i) on lettuce cultivars varied between 1 and 3. In three experiments with butterhead lettuce ‘Cosmopolia’ in pots with a series of 9 or 10 densities of Paratylenchus sp. [up to 35,000 (100 ml soil)^?1], no damage to lettuce heads was observed. However, root weight and root quality were reduced, and the corresponding damage thresholds were rather low [1,754 and 362 Paratylenchus sp. (100 ml soil)^?1, respectively]. Management strategies such as crop rotation, soil disinfestation or fallow are recommended to avoid pin nematode population build‐up.     

Observations onColeoscirus simplex (Acarina: Prostigmata), a predatory mite that colonizes greenhouse cultures of rootknot nematode (Meloidogyne spp.), and a review of feeding behavior in the Cunaxidae

Coleoscirus simplex (Ewing) · (Cunaxidae: Coleoscirinae) colonizes greenhouse pot cultures of rootknot nematodes (Meloidogyne spp.) in Orlando, Florida, where it preys on vermiform nematodes and soil arthropods. This is the first report of nematophagy in a cunaxid mite.Mating was required for oviposition inC. simplex. An average of 4.4 eggs were laid per day, and mean generation time was 14.3 days at 28°C. A silken web was spun around the mite and the end of each active instar.Coleoscirus simplex fed near the top of the food web that colonized rootknot nematode cultures, but feeding relationships were complex. Size, degree of sclerotization, speed, and availability of alternative prey influenced predatory success. Cannibalism was common, including attacks on quiescent immatures in the molting web.Coleoscirus simplex did not feed on the eggs of either rootknot nematodes or arthropods. Neoscirula sp. (Coleoscirinae) andPulaeus sp. (Cunaxoidinae) also fed on both arthropods and nematodes, but three species in the Cunaxinae,Dactyloscirus inermis (Tragardh),Dactyloscirus sp., andCunaxa sp., fed only on arthropods.     

Correlation of Edaphic Factors with Plant-parasitic Nematode Population Densities in a Forage Field

Two hundred soil samples from the A_p horizon of a reed canarygrass field overlaying several different but related soils in northern Minnesota were analyzed for plant-parasitic nematodes and 22 edaphic factors. Pratylenchus penetrans was the predominant nematode taxon. Others were Aglenchus agricola, Tylenchorhynchus spp., Heterodera trifolii, Paratylenchus spp., Tylenchus maius, and Criconemella sp. Five nematode taxa, P. penetrans, A, agricola, Tylenchorhynchus spp., H. trifolii, and Paratylenchus spp., were correlated with particle size, Tylenchus maius and Criconemella sp. were correlated with effective cation exchange capacity. Nematode field spatial arrangements were related to a combination of statistically significant positive and negative soil factor effects on the nematode populations. Contour maps derived by geostatistical techniques were used to visually validate statistically significant correlations of nematode and soil data. Contour mapping to supplement traditional statistical techniques can be used to achieve a more holistic approach to studies of nematode-soil interrelationships.     

Distribution of ectomycorrhizal and pathogenic fungi in soil along a vegetational change from Japanese black pine (Pinus thunbergii) to black locust (Robinia pseudoacacia)

The nitrogen-fixing tree black locust (Robinia pseudoacacia L.) seems to affect ectomycorrhizal (ECM) colonization and disease severity of Japanese black pine (Pinus thunbergii Parl.) seedlings. We examined the effect of black locust on the distribution of ECM and pathogenic fungi in soil. DNA was extracted from soil at depths of 0–5 and 5–10 cm, collected from the border between a Japanese black pine- and a black locust-dominated forest, and the distribution of these fungi was investigated by denaturing gradient gel electrophoresis. The effect of soil nutrition and pH on fungal distribution was also examined. Tomentella sp. 1 and Tomentella sp. 2 were not detected from some subplots in the Japanese black pine-dominated forest. Ectomycorrhizas formed by Tomentella spp. were dominant in black locust-dominated subplots and very little in the Japanese black pine-dominated forest. Therefore, the distribution may be influenced by the distribution of inoculum potential, although we could not detect significant relationships between the distribution of Tomentella spp. on pine seedlings and in soils. The other ECM fungi were detected in soils in subplots where the ECM fungi was not detected on pine seedlings, and there was no significant correlation between the distribution of the ECM fungi on pine seedlings and in soils. Therefore, inoculum potential seemed to not always influence the ECM community on roots. The distribution of Lactarius quieticolor and Tomentella sp. 2 in soil at a depth of 0–5 cm positively correlated with soil phosphate (soil P) and that of Tomentella sp. 2 also positively correlated with soil nitrogen (soil N). These results suggest the possibility that the distribution of inoculum potential of the ECM fungi was affected by soil N and soil P. Although the mortality of the pine seedlings was higher in the black locust-dominated area than in the Japanese black pine-dominated area, a pathogenic fungus of pine seedlings, Cylindrocladium pacificum, was detected in soil at depths of 0–5 and 5–10 cm from both these areas. This indicates that the disease severity of pine seedlings in this study was influenced by environmental conditions rather than the distribution of inoculum potential.     

松材线虫侵染的马尾松人工林细根形态及生物量分异特征

中龄林的马尾松受松材线虫侵染后,林木生长、生理生化指标、群落多样性等会发生异质性变化,但是,针对患病林木地下细根的响应尚不清楚。本研究以松材线虫疫区患病马尾松和健康马尾松为研究对象,采用土柱法,分0-15 cm和15-30 cm土层,对细根进行分级研究,定量分析1-5级细根的形态、生物量以及养分元素,探讨松材线虫侵染的马尾松人工林细根形态、生物量以及养分元素的分异特征。结果表明:(1)患病马尾松人工林细根的健康状态与根长密度、生物量呈极显著正相关(P<0.01),低级根(如1级根)患病后,响应会更加强烈。(2)马尾松人工林患病后,细根有效磷、速效钾浓度会显著降低(P<0.05),而全氮、钙浓度会显著升高(P<0.05)。(3)松材线虫病使林分的土壤有机质含量显著高于健康林分(P<0.05),而土壤速效钾含量会显著低于健康林分(P<0.05)。以上结果表明,松材线虫侵染的马尾松人工林会在细根形态、细根养分和土壤养分上会发生特异性响应,揭示了松材线虫病对马尾松人工林地下细根的影响,旨在为松材线虫病防治提供一定参考。     

Ants protect conifer seedlings from feeding damage by the pine weevil Hylobius abietis

• 1 Ants that protect food resources on plants may prey on (or deter) herbivores and thereby reduce damage. Red wood ants (of the Formica rufa group) are dominant ants in boreal forests of Eurasia and affect the local abundance of several herbivorous species.
• 2 The pine weevil Hylobius abietis (L.) is a herbivore that causes severe damage by feeding on the bark of coniferous seedlings within areas of forest regeneration.
• 3 We investigated whether ants can protect conifer seedlings from pine weevil feeding. In a manipulative experiment, ants were attracted to sugar baits attached to spruce seedlings and the damage caused by pine weevils was compared with control seedlings without ant‐baits.
• 4 The feeding‐scar area was approximately one‐third lower on the seedlings with ant‐baits compared with the controls. Besides red wood ants, Myrmica ants were also attracted in high numbers to the ant baits and the relative effects of these species are discussed.
• 5 The results obtained in the present study support the trophic cascade hypothesis (i.e. damage to herbivores is suppressed in the presence of predators). The decreased pine weevil feeding on the baited seedlings was probably a result of nonconsumptive interactions [i.e. the presence of (or harassment by) ants distracting pine weevils from feeding].
• 6 Understanding the role of ants may have important implications for future strategies aiming to control pine weevil damage. For example, maintaining suitable conditions for ants after harvesting stands may be an environmentally friendly but currently unexploited method of for decreasing weevil damage.

     

Small mammal responses to moose supplementary winter feeding

Supplementary feeding of wild large herbivores is a widespread practice in North America and Europe. The presence of feeding stations may have ecological consequences through changes to animal distributions, patterns of herbivory and a net nutrient input into the ecosystem. In Fennoscandia, supplementary feeding of moose in winter (Alces alces) is increasing. Although it has been shown to affect bird communities, its effects on small mammal communities were unknown. Here, we studied the effects of moose supplementary feeding stations on plants and on abundance, reproduction, and biomass of small mammals in years with low and high vole abundance. We sampled small mammals with snap traps and conducted surveys of the field layer vegetation, at varying distances from moose supplemental feeding stations. Due to the vegetation changes induced by feeding stations, abundance of common shrews (Sorex araneus) and Microtus voles were positively affected by long-term moose winter feeding, while bank voles (Myodes glareolus) were not affected. Moose feeding stations did not affect reproduction, individual body mass, or the total biomass of small mammals. Moose winter-feeding stations have impacts on nontarget species, providing islands of preferred grass and forb habitat for Microtus spp. and common shrews, allowing them to penetrate into a matrix of less preferred forest habitat.     

Plant diversity and identity effects on predatory nematodes and their prey

There is considerable evidence that both plant diversity and plant identity can influence the level of predation and predator abundance aboveground. However, how the level of predation in the soil and the abundance of predatory soil fauna are related to plant diversity and identity remains largely unknown. In a biodiversity field experiment, we examined the effects of plant diversity and identity on the infectivity of entomopathogenic nematodes (EPNs, Heterorhabditis and Steinernema spp.), which prey on soil arthropods, and abundance of carnivorous non‐EPNs, which are predators of other nematode groups. To obtain a comprehensive view of the potential prey/food availability, we also quantified the abundance of soil insects and nonpredatory nematodes and the root biomass in the experimental plots. We used structural equation modeling (SEM) to investigate possible pathways by which plant diversity and identity may affect EPN infectivity and the abundance of carnivorous non‐EPNs. Heterorhabditis spp. infectivity and the abundance of carnivorous non‐EPNs were not directly related to plant diversity or the proportion of legumes, grasses and forbs in the plant community. However, Steinernema spp. infectivity was higher in monocultures of Festuca rubra and Trifolium pratense than in monocultures of the other six plant species. SEM revealed that legumes positively affected Steinernema infectivity, whereas plant diversity indirectly affected the infectivity of Heterorhabditis EPNs via effects on the abundance of soil insects. The abundance of prey (soil insects and root‐feeding, bacterivorous, and fungivorous nematodes) increased with higher plant diversity. The abundance of prey nematodes was also positively affected by legumes. These plant community effects could not be explained by changes in root biomass. Our results show that plant diversity and identity effects on belowground biota (particularly soil nematode community) can differ between organisms that belong to the same feeding guild and that generalizations about plant diversity effects on soil organisms should be made with great caution.     

Establishment and yield of three ryegrasses following aldicarb use, and changes in abundance of plant parasitic nematodes

Pure swards of Lolium multiflorum, L. multiflorum var. westerwoldicum and L. perenne sown in August had greater yields than autumn on areas treated with either 5 or 10 kg a.i./ha aldicarb than on untreated areas. Total annual dry matter yields increased by larger amounts where the greater rate of aldicarb was applied; throughout the trial, L. perenne was usually less affected by treatment than the other two grasses. Plant-parasitic nematodes were more numerous on untreated than treated plots and were fewest in areas receiving the larger application (except in the second harvest year). Numbers of Tylenchorhynchus and Helicotylenchus were affected most by treatments; abundance of Paratylenchus and Criconemella were little altered. Stem-boring Diptera invaded tillers of all three grasses but infection was least in L. perenne. Invasion occurred only on untreated plots in the establishment year and some yield benefit probably resulted from their control. In subsequent years invasion was similar on treated and untreated areas. Effects on other, non-target organisms were not assessed. Ectoparasitic nematodes multiplied more in L. multiflorum plots than in others during the first full-harvest year. The next year numbers of Paratylenchus only were greater in plots of L. perenne than in other plots. Sward persistence of L. multiflorum var. westerwoldicum was better on treated than untreated areas. It was concluded a) that aldicarb use greatly decreased nematode numbers and yields from treated areas were larger than from those untreated; b) that sward persistence was similarly improved following aldicarb use and c) that ryegrasses differed in their suitability as hosts to ectoparasitic nematodes.