Response of a nematode community to the fungicide fludioxonil in sediments of outdoor freshwater microcosms compared to a single species toxicity test
Höss, S. ; Roessink, I. ; Brock, T.C.M. ; Traunspurger, W. - \ 2020
Science of the Total Environment 710 (2020). - ISSN 0048-9697
Caenorhabditis elegans - Fludioxonil - Nematodes - Outdoor microcosms - Spiked sediment
When entering aquatic ecosystems, hydrophobic organic chemicals like the fungicide fludioxonil partition to the sediment compartment where they pose potential risks to benthic invertebrates. To assess the ecological risk for sediment-dwelling invertebrates, nematodes are a suitable organism group, as they are abundantly present and possess key positions in the benthic food web. Therefore, the toxicity of the fungicide fludioxonil to nematodes was assessed in a standardized sediment toxicity test with Caenorhabditis elegans (ISO 10872), as well as in an outdoor sediment-spiked microcosm test system. In the microcosms, effects on the nematode species composition were studied, while exposure concentrations of fludioxonil were monitored in total sediment and pore water. Toxic effects on nematodes were better predicted using concentrations in pore water than total sediment concentrations. In laboratory single species tests, fludioxonil showed considerably lower toxicity in spiked field-collected sediment, compared to artificial ISO-sediments. Applying an assessment factor of 10 to the C. elegans 96-h EC10, a Tier-1 RACNematode of 7.99 mg kg−1 dry artificial sediment (corresponding to 69 μg l−1 in pore water) appeared to be protective for nematode communities in microcosms that showed no response in total abundance and species composition up to 39.9 mg fludioxonil kg−1 dry sediment (corresponding to 392 μg l−1 in pore water).
A review of the apple sawfly, hoplocampa testudinea (Hymenoptera tenthredinidae)
Vincent, Charles ; Babendreier, Dirk ; Świergiel, Weronika ; Helsen, Herman ; Blommers, Leo H.M. - \ 2019
Bulletin of Insectology 72 (2019)1. - ISSN 1721-8861 - p. 35 - 54.
Apple orchards - Apple sawfly - Aptesis nigrocincta - Hoplocampa testudinea - Lathrolestes ensator - Nematodes
The apple sawfly (ASF), Hoplocampa testudinea Klug (Hymenoptera Tenthredinidae), attacks only one host plant, the apple tree (Malus domestica Borkh.). It is found in temperate regions of Europe as well as in Eastern North America. The flight of the ASF adults coincides with the bloom of apple trees and larvae develop in fruitlets. As the ASF spends approximately 11 months of its life cycle underground as a pre-pupa or pupa, management of the ASF is possible only during 1 month. The ASF is univoltine and has an obligatory diapause that can be extended to 2, 3 or rarely 4 years. Here key publications about the ASF have been selected for their relevance to the application of Integrated Pest Management programs. Because the ASF is dependent on living and developing tissues and because no oviposition or artificial diet is available for laboratory experimentations, research projects have to be conducted in field or semi-field conditions. The main natural mortality factors are the ichneumonid parasitoids Lathrolestes ensator (Brauns), present in Europe and introduced to Eastern Canada, and Aptesis nigrocincta (Gravenhorst) in Europe. The latter also acts as a hyperparasitoid of L. ensator. Management of the ASF can be based on monitoring adults with sticky traps and with use of a simulation model. Non-insecticidal methods that can be used deliberately in an ASF management program are reviewed, notably nematodes, entomopathogenic fungi, and physical control methods such as cellulose barriers and exclusion netting. The technical and economic reasons preventing widespread implementation of these approaches are discussed.
The impact of dispersal, plant genotype and nematodes on arbuscular mycorrhizal fungal colonization
Rasmussen, Pil U. ; Chareesri, Anupol ; Neilson, Roy ; Bennett, Alison E. ; Tack, Ayco J.M. - \ 2019
Soil Biology and Biochemistry 132 (2019). - ISSN 0038-0717 - p. 28 - 35.
Arbuscular mycorrhizal fungi - Colonization ability - Dispersal - Genotype - Nematodes - Plantago lanceolata
While the majority of parasitic and mutualistic microbes have the potential for long-range dispersal, the high turnover in community composition among nearby hosts has often been interpreted to reflect dispersal constraints. To resolve this apparent contradiction, we need further insights into the relative importance of dispersal limitation, host genotype and the biotic environment on the colonization process. We focused on the important root symbionts, the arbuscular mycorrhizal (AM) fungi. We studied AM fungal colonization ability in a controlled mesocosm setting, where we placed Plantago lanceolata plants belonging to four different genotypes in sterile soil at 10, 30 and 70 cm from a central AM fungal inoculated P. lanceolata plant. In part of the mesocosms, we also inoculated the source plants with nematodes. AM fungi colonized receiver plants <1 m away over the course of ten weeks, with a strong effect of distance from source plant on AM fungal colonization. Plant genotype influenced AM fungal colonization during the early stages of colonization, while nematode inoculation had no effect on AM fungal colonization. Overall, the effect of both dispersal limitation and plant genetic variation may underlie the small-scale heterogeneity found in natural AM fungal communities.
Integrating quantitative morphological and qualitative molecular methods to analyse soil nematode community responses to plant range expansion
Geisen, Stefan ; Snoek, L.B. ; Hooven, Freddy C. ten; Duyts, Henk ; Kostenko, Olga ; Bloem, Janneke ; Martens, Henk ; Quist, Casper W. ; Helder, Johannes A. ; Putten, Wim H. van der - \ 2018
Methods in Ecology and Evolution 9 (2018)6. - ISSN 2041-210X - p. 1366 - 1378.
Biodiversity - High-throughput sequencing - Microscopy - Molecular approaches - Nematodes - QPCR - Soils
Below-ground nematodes are important for soil functioning, as they are ubiquitous and operate at various trophic levels in the soil food web. However, morphological nematode community analysis is time consuming and requires ample training. qPCR-based nematode identification techniques are well available, but high-throughput sequencing (HTS) might be more suitable for non-targeted nematode community analyses. We compared effectiveness of qPCR- and HTS-based approaches with morphological nematode identification while examining how climate warming-induced plant range expansion may influence below-ground nematode assemblages. We extracted nematodes from soil of Centaurea stoebe and C. jacea populations in Slovenia, where both plant species are native, and Germany, where C. stoebe is a range expander and C. jacea is native. Half of each nematode sample was identified morphologically and the other half was analysed using targeted qPCR and a novel HTS approach. HTS produced the highest taxonomic resolution of the nematode community. Nematode taxa abundances correlated between the methods. Therefore, especially relative HTS and relative morphological data revealed nearly identical ecological patterns. All methods showed lower numbers of plant-feeding nematodes in rhizosphere soils of C. stoebe compared to C. jacea. However, a profound difference was observed between absolute and relative abundance data; both sampling origin and plant species affected relative abundances of bacterivorous nematodes, whereas there was no effect on absolute abundances. Taken together, as HTS correlates with relative analyses of soil nematode communities, while providing highest taxonomic resolution and sample throughput, we propose a combination of HTS with microscopic counting to supplement important quantitative data on soil nematode communities. This provides the most cost-effective, in-depth methodology to study soil nematode community responses to changes in the environment. This methodology will also be applicable to nematode analyses in aquatic systems.
Responses of soil biota to non-inversion tillage and organic amendments : An analysis on European multiyear field experiments
Hose, Tommy D'; Molendijk, Leendert ; Vooren, Laura Van; Berg, Wim van den; Hoek, Hans ; Runia, Willemien ; Evert, Frits van; Berge, Hein ten; Spiegel, Heide ; Sandèn, Taru ; Grignani, Carlo ; Ruysschaert, Greet - \ 2018
Pedobiologia 66 (2018). - ISSN 0031-4056 - p. 18 - 28.
Earthworms - Microbial biomass - Multiyear field experiments - Nematodes - Non-inversion tillage - Organic amendments
Over the last two decades, there has been growing interest on the effects of agricultural practices on soil biology in Europe. As soil biota are known to fluctuate throughout the season and as agro-environmental conditions may influence the effect of agricultural practices on soil organisms, conclusions cannot be drawn from a single study. Therefore, integrating the results of many studies in order to identify general trends is required. The main objective of this study was to investigate how soil biota are affected by repeated applications of organic amendments (i.e. compost, farmyard manure and slurry) or reduced tillage (i.e. non-inversion tillage and no till) under European conditions, as measured in multiyear field experiments. Moreover, we investigated to what extent the effects on soil biota are controlled by soil texture, sampling depth, climate and duration of agricultural practice. Experimental data on earthworm and nematode abundance, microbial biomass carbon and bacterial and fungal communities from more than 60 European multiyear field experiments, comprising different climatic zones and soil texture classes, were extracted from literature. From our survey, we can conclude that adopting no tillage or non-inversion tillage practices and increasing organic matter inputs by organic fertilization were accompanied by larger earthworm numbers (an increase between 56 and 125% and between 63 and 151% for tillage and organic amendments, respectively) and biomass (an increase between 108 and 416% and between 66 and 196% for tillage and organic amendments, respectively), a higher microbial biomass carbon content (an increase between 10 and 30% and between 25 and 31% for tillage and organic amendments, respectively), a marked increase in bacterivorous nematodes (an increase between 19 and 282% for organic amendment) and bacterial phospholipid-derived fatty acids (PLFA; an increase between 31 and 38% for organic amendment). Results were rarely influenced by soil texture, climate and duration of practice.
The need for standardisation: Exemplified by a description of the diversity, community structure and ecological indices of soil nematodes
Griffiths, B.S. ; Groot, G.A. de; Laros, I. ; Stone, D. ; Geisen, S. - \ 2018
Ecological Indicators 87 (2018). - ISSN 1470-160X - p. 43 - 46.
Biodiversity - DNA extraction - Metabarcoding - Microscopy - Molecular approaches - Nematodes - Standardisation
Molecular approaches are offering a supplement to, or even the possibility of replacing morphological identification of soil fauna, because of advantages for throughput, coverage and objectivity. We determined ecological indices of nematode community data from four sets of duplicate soil cores, based on morphological identification of nematodes after elutriation from 200 g soil and high throughput sequencing (HTS) targeting nematodes both after being elutriated from soils and DNA extracted directly from 10 g soil. HTS (at genus and species level) increased the taxonomic resolution compared to morphology (at family level). DNA extracted from elutriated nematodes identified more nematode taxa than when extracted from soil, due to an enrichment in nematode sequences. Each method also gave a different ecological footprint for the nematode community. Standardisation to previously determined indices based on morphological identification is needed in order to provide more meaningful information about soil quality and for ecological monitoring.
Controlled Atmosphere Temperature Treatment : Non-chemical (quarantine) pest control in fresh plant products
Verschoor, J.A. ; Otma, E.C. ; Qiu, Y.T. ; Kruistum, G. Van; Hoek, J. - \ 2015
Acta Horticulturae 1071 (2015). - ISSN 0567-7572 - p. 253 - 258.
Insects - Nematodes - Phytosanitation
Insects, nematodes and mites that damage postharvest plant products can cause severe quality losses or trade restrictions in case of quarantine organisms. With the ban of the ozone depleting methyl bromide (MeBr), the most widely used chemical for phytosanitary treatments, effective and sustainable alternatives are required. A physical method, Controlled Atmosphere Temperature Treatment (CATT) can be a sustainable alternative for the control of pests on living plant products. Optimising CA-conditions besides temperature and exposure time can help in developing successful applications. In The Netherlands, a successful application to disinfest strawberry (Fragaria × ananassa) planting material from strawberry tarsonemid mite (Phytonemus pallidus) or plant parasitic nematodes Meloidogyne hapla was developed and implemented in practice. Initial tests with a number of other potential quarantine plant-pest combinations showed promising results of CATT.
Coprophagy in dogs interferes in the diagnosis of parasitic infections by faecal examination
Nijsse, R. ; Mughini-Gras, L. ; Wagenaar, J.A. ; Ploeger, H.W. - \ 2014
Veterinary Parasitology 204 (2014)3-4. - ISSN 0304-4017 - p. 304 - 309.
Coprophagy - Coproscopical examination - Dogs - Nematodes - Roundworms - Toxocara
Many dogs display coprophagic behaviour. Helminth eggs can passively pass the dog's digestive tract and this may result in a false positive diagnosis of infection with gastrointestinal helminth parasites. For a period of one year, faecal samples of dogs were examined monthly using the Centrifugal Sedimentation Flotation (CSF) technique with a sugar flotation solution (s.g. 1.27-1.30 g/cm(3)). If a sample tested positive for canine helminth eggs, the owner was asked to submit another sample after preventing the dog from eating faeces for 3 days. If the second sample again tested positive for the same type of helminth egg, the dog was considered to have a patent infection. If the second sample tested negative, the first sample was considered a false positive due to coprophagy. The focus of this study was on dogs shedding Toxocara eggs. At the first examination, 246 samples (out of 308 samples testing positive for canine-specific helminth eggs) tested positive for Toxocara spp. Of these, 120 (49%) tested negative at the second examination. Coprophagic behaviour was recognized by 261 of the 564 owners that answered the accompanying questionnaire. This concerned 391 dogs. Coproscopical examination also provided proof of coprophagy (e.g. oocysts of Eimeria spp. or non-dog typical helminth eggs) in dogs belonging to owners that did not report coprophagic behaviour in their dogs. Results indicate that coprophagy in dogs may result in an overestimation of the prevalence of patent helminth infections and that dogs may serve as a transport host for helminth eggs.