Soil Nematode Populations Beneath Faecal Pats from Grazing Cattle Treated with the Ivermectin Sustained-release Bolus or Fed the Nematophagous Fungus Duddingtonia flagrans to Control Nematode Parasites (original) (raw)
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Pathogens
The purpose of using nematophagous fungi as biological control agents of gastrointestinal nematodes of livestock is to reduce the build-up of infective larvae on pasture and thus avoid clinical and subclinical disease. As the interaction of fungus-larval stages takes place in the environment, it is crucial to know how useful the fungal agents are throughout the seasons in areas where livestock graze all year-round. This study was designed to determine the predatory ability of the nematophagous fungus Duddingtonia flagrans against gastrointestinal nematodes of cattle during four experiments set up in different seasons. In each experiment, faeces containing eggs of gastrointestinal nematodes were mixed with 11,000 chlamydospores/g and deposited on pasture plots. A comparison between fungal-added faeces and control faeces without fungus were made with regard to pasture infectivity, larval presence in faecal pats, faecal cultures, faecal pat weight, and temperature inside the faecal mas...
The possible environmental effects of the massive use of Duddingtonia flagrans for controlling sheep nematodes were evaluated in two regions. Non-supplemented faeces and faeces from sheep supplemented with D. flagrans were deposited three times on pasture plots and samples were collected 7 and 14 days post-deposition. Samples were cultured in agar-water (2%) with Panagrellus spp. to recover D. flagrans and other nematophagous fungi, and soil nematodes were extracted using Baermann funnels and counted. No significant differences in the populations of soil nematodes and fungi colonizing sheep faeces (P. 0.05) were observed between supplemented and non-supplemented groups, except in one sample. The topsoil in contact with the faeces was sampled 1 –4 months post-deposition, revealing that, with one exception, D. flagrans did not persist in soil beyond 2 months post-deposition. Duddingtonia flagrans does not affect faecal colonization by other fungi and soil nematodes and, once deployed on pasture, does not survive for long periods in the environment.
Veterinary Parasitology, 1997
A plot experiment was conducted to investigate the ability of the nematode-trapping fungus Duddingtonia flagrans to reduce the transmission of infective horse strongyle larvae from deposited dung onto surrounding herbage. At three different times during the summer 1995, three groups of horses, naturally infected with large and small strongyles, were fed different doses of D. flagrans spores, while a fourth group of animals served as non-fungal controls. Faeces from all four groups of horses were deposited as artificial dung pats on a parasite-free pasture. Every second week for 8 weeks after dung deposition, a subsample of the herbage surrounding each dung pat was collected and the number of larvae on the grass determined. Also, the larval reduction capacity of the fungus was evaluated by faecal cultures set up from all groups of horses. The faecal cultures showed that a sufficient number of spores of D. flagrans survived passage through the horses alimentary tract to significantly reduce the number of developing larvae. A lower reduction of larval numbers was observed when a different batch of fungal material was used at the beginning of the season. Dry climatic conditions affected the transmission of infective larvae in all groups, resulting in low numbers of larvae on the herbage. During the rainy periods a significant reduction in the number of larvae recovered was observed around all fungal containing pats. There were no significant differences between the number of fungal spores and the level of reduction caused by the fungus.
Soil nematodes in the field and fallow - density and diversity
2020
The results presented here concern the study, which was carried out in the spring of 2009 on an arable field and a fallow. Following parameters were analysed: density, taxonomic composition, trophic and dominance structure of soil nematode communities. Shannon-Weaver diversity index, Sørensen’s index of similarity and Maturity index were also calculated. The results show that the nematode community in the soil of arable field differed from that on the fallow in respect of density and trophic structure. Nematode density was higher in the arable soil than in the fallow. The group of bacterial-feeding nematodes was the most numerous among five trophic groups recorded in the study. The higher density of that group in the arable soil than in the fallow indicates the positive response of bacterial-feeding nematodes to the higher nutrient supply after the manure applying. The results show that in three years of fallow nematode communities became more mature and diverse than in the arable s...
The ability of the nematode-trapping fungus Duddingtonia flagrans to reduce the transmission of
Journal of Helminthology, 1999
The ability of two isolates of the nematode-trapping fungus Duddingtonia flagrans to reduce the numbers of gastrointestinal nematode larvae on herbage was tested in three plot studies. Artificially prepared cow pats containing Ostertagia ostertagi eggs, with and without fungal spores, were deposited on pasture plots two or three times during the grazing season in 1995, 1996 and 1997. The herbage around each pat was sampled fortnightly over a period of 2 months and the number of infective larvae was recorded. At the end of the sampling period, the remainder of the faecal pats was collected to determine the wet weight, dry weight, and content of organic matter. The infective larvae remaining in the pats were extracted. Faecal cultures showed that both fungal isolates significantly reduced the number of infective larvae. Significantly fewer larvae were recovered from herbage surrounding fungus-treated pats compared with control pats in all three experiments, reflecting the ability of t...
Veterinary parasitology, 2004
Infection with gastrointestinal nematodes, particularly Haemonchus contortus, is a major constraint to goat production in the southeastern United States. Non-anthelmintic control alternatives are needed due to increasing resistance of these nematodes to available anthelmintics. Two studies were completed in Central Georgia in August 1999, and April-May 2000, using Spanish does naturally infected with Haemonchus contortus, Trichostongylus colubriformis, and Cooperia spp. to evaluate effectiveness of nematode-trapping fungi as a biological control agent. In the first experiment, five levels of Duddingtonia flagrans spores were mixed with a complete diet and fed once daily to the does (three per treatment) in metabolism crates. The treatment concentrations were (1) 5 x 10(5), (2) 2.5 x 10(5), (3) 10(5), and (4) 5 x 10(4) spores per kilogram body weight (BW), and (5) no spores. Fungal spores were fed for the first 7 days of the 14-day trial, and fecal samples were collected daily from i...
Soil sustainability implies a sufficient diversity and abundance of organisms to perform soil functions and to resist environmental stress. Previous studies have shown the importance of functional biodiversity for soil organisms. 2. Soil samples have been collected within the framework of a long-term monitoring programme in the Netherlands. Nematological and microbiological techniques were combined to facilitate a more comprehensive understanding of possible below-ground effects of land management. 3. A possible bias due to stochastic circumstances was investigated. The Mantel test showed that the diversity at species level is largely related to air temperature, but at genus level the effect of temperature disappears. No direct influence of rainfall on the soil biodiversity was found in our model. 4. To extrapolate our data to a national level, habitat-response relationships for soil organisms have been derived. Generalized linear models (GLMs) and Monte Carlo simulation allowed the estimation of the probability of occurrence at a given abundance for 95 nematode genera. 5. Our study describes the influence of abiotic conditions and land use intensity on the composition of nematode communities in grasslands on sand. The results obtained reveal a major influence of pH and livestock density on the diversity of the nematode community at both taxonomic levels as well as at different trophic levels (feeding habits). The presence and abundance of soil nematodes decrease with cattle pressure. 6. Functional diversity decreases with increasing management intensity. It is shown that the Shannon diversities of bacterial feeding nematodes and fungal feeding nematodes are strictly related to cattle pressure, whereas the bacterial biomass occurring under organic farming scores higher than in other farming systems.
2011
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Resiliency of a nematode community and suppressive service to tillage and nematicide application
Applied Soil Ecology, 2012
We hypothesized that populations of predatory and omnivorous nematodes would be slower to recover from conventional tillage and nematicide application than other nematode trophic groups, and that lower populations of predators and omnivores would lead to greater survival and reproduction of plantfeeding nematodes (i.e., pest resurgence). A field study was conducted from 2008 to 2010 with two tillage regimes (strip and conventional) and two nematicide treatments (1,3-dichloropropene + aldicarb and a no-nematicide control) with six replications arranged in a split-plot design. Soil samples were collected pre-fumigation/tillage, post plant, and mid season during each year. Nematodes were extracted from soil and identified to genus. The field site had relatively high populations of predatory and omnivorous nematodes and abundance of these feeding groups translated into a relatively high Structure Index (≥60) in the control plots. Tillage had little impact on the nematode community, but the nematicides reduced numbers of all trophic groups compared to the control at post plant and mid season. However, for bacterial and plant feeders, there was also a consistent lingering effect of the nematicides the following year at pre-fumigation. Omnivores and predators were not severely impacted by the nematicide treatment; populations of both groups repeatedly recovered by the following spring from the yearly application of nematicides, with the exception of predators in 2008. We used two bioassays to measure the suppressive service of the soil community: one determined survival of the reniform nematode (Rotylenchulus reniformis) and the other reproduction of Meloidogyne arenaria on peanut. Survival of R. reniformis was greater in defaunated compared to native soil indicating that the soil contained organisms that consumed nematodes. Application of nematicides led to an increase in survival of the R. reniformis from 53% in the control to 78% in treated plots at post plant, and from 55% in the control plots to 66% in treated plots at mid season. Likewise, reproduction of M. arenaria was greater in soil treated with nematicides. At post plant, survival (%) of R. reniformis was negatively correlated with abundance of predators + omnivores. Organisms other than nematodes were likely involved in the suppressive service. This was particularly evident at pre-fumigation/tillage, when survival of R. reniformis was lower in plots previously treated with nematicides than in control plots. The nematicides may have altered the soil community to allow a fungal, bacterial, or invertebrate antagonist of nematodes to increase in abundance.