Progress 09/01/04 to 06/30/07
Outputs
OUTPUTS: This project involved novel ecological research to identify the habitat characteristics needed for persistence of entomopathogenic nematode (EPN) populations in agroecosystems. To determine how these factors influence EPN persistence, individually and particularly in combination, we conducted a systematic survey for naturally occurring nematode populations in an Ohio vegetable production landscape with sample sites chosen to achieve gradients in a wide range of biotic and abiotic environmental conditions. During October - December 2004, we conducted the initial intensive survey, taking 100 soil samples in each of 6 landscape classes. Naturally occurring EPNs were confirmed in 42 of the samples, representing 5 of the 6 landscape classes but predominating in minimally maintained grassy areas. Free-living nematodes were extracted from each soil sample and identified to family and classified according to functional group. Measurements of soil chemical and physical and microbial
biomass were taken for each sample. Data on nematode species and environmental conditions have been analyzed by multivariate statistical techniques specifically designed to estimate the relative importance of a number of environmental conditions in explaining variation in abundance or occurrence of multiple species at a number of sample sites (described in the introduction). A subset of 144 sites was selected based on the analysis results and these were sampled for soil abiotic and biotic conditions, arthropod communities and EPN populations over time. Results of the project were disseminated in 3 forms: presentations at professional society meetings, presentations at grower/producer meetings, and publications in scientific journals. Scientific meeting presentations included the Annual Meeting of the Society for Invertebrate Pathology, Anchorage, AK 11 August 2005, and Quebec City, QC, 18 August 2007; the CSREES Awardee Workshop on Biologically-based Pest Management, Ft. Lauderdale,
FL, 14 December 2005 and Ventura, CA, 18 February 2007; and the Annual Meeting of the Entomological Society of America, Ft. Lauderdale, FL, 15-18 December 2005. Extension meetings included the annual Ohio Muck Crops School and Ohio Vegetable and Potato Growers Association Annual Conference. Publications are listed below.
PARTICIPANTS: Casey Hoy - PI, Directed the overall project, supervised the schedule of research activities and field operations, conducted the statistical analysis, particularly the multivariate analysis. Parwinder Grewal - coPI, Co-director for the overall project and supervised the laboratory aspects of the project, particularly the nematology, nematode identification and quantification. Janet Lawrence - Postdoctoral researcher, supervised the initial 600-site survey and data collection. Gained valuable experience in the logistics of this kind of field research. Ganpati Jagdale - Postdoctoral researcher, Conducted the laboratory research on the project, particularly the nematode extraction, identification and quantification. Conducted experiments on the impact of soil biota on nematode survival. Nuris Acosta - Research Assistant - Conducted field surveys, supervised sampling of 144 sites in years 2 and 3, identified insects collected, processed soil samples for the soils
laboratory. Partners in the project were collaborating farmers in the Willard, OH area: Buurma Farms, Wiers Farms, Holthouse Farms, and J. F. Stanbaugh & Co.
TARGET AUDIENCES: The scientific community, particularly those working on soil ecology and entomopathogenic nematodes, was one key target audience. Presentations and publications have created new interest in the ecology of these species and potential for conservation biological control approaches. Vegetable growers, particularly in the Great Lakes region, are the second key target audience. Presentations at regional grower meetings has stimulated interest in biological controls for soil insect pests.
Impacts
The following results from the project have shifted research focus from the use of EPN's as biological insecticides to a conservation biological control strategy in which naturally occurring populations can be managed to provide biological control services. Naturally occurring entomopathogenic nematodes were confirmed in 43 of the 600+ samples, representing all but the vegetable crop habitats and with the greatest number of positive sites in minimally maintained grassy areas. Data on nematode species and environmental conditions have been analyzed by canonical correspondence analysis, specifically designed to estimate the relative importance of a number of environmental conditions in explaining variation in abundance or occurrence of multiple species at a number of sample sites. Approximately 80% of the variation in the species-environment relationship could be explained by the combination of environmental variables. The variables identified as being the most important
in shifting from the vegetable field conditions to those present in the grassy borders were increased structure and enrichment in the soil food web, lower carbon:nitrogen ratios, increased K and decreased P. EPN's occupied a very different profile of soil conditions from other species of free-living nematodes. EPN populations varied over time, with detection occurring at least once in 56 of the 144 sites, but only in 3 of the 144 sites for all 7 sample dates. Patterns of occurrence in time and space are consistent with metapopulation dynamics. Principal response curve analysis demonstrated greater arthropod abundance of diverse arthropod taxa in EPN positive than negative sites, and association with arthropod detritivores more so than herbivores.
Publications
- Stuart, R. J., M. E. Barbercheck, P. S. Grewal , R. A. J. Taylor , and C. W. Hoy. 2006. Population Biology of Entomopathogenic Nematodes: Concepts, Issues and Models. Biological Control. 38: 80-102.
- Lawrence, J. L., C. W. Hoy and P. Grewal. 2006. Spatial and temporal distribution of endemic entomopathogenic nematodes in a heterogeneous vegetable production landscape. Biological Control. 37: 247-255.
- Alumai, A., P. S. Grewal, C. W. Hoy and D. A. Willoughby. 2006. Factors affecting the natural occurrence of entomopathogenic nematodes in turfgrass. Biological Control. 368-374.
- Briar, S. S., Jagdale, G. B., Cheng, Z, Hoy, C. W., Miller, S. A. & Grewal, P. S. 2007. Indicative value of nematode food web indices and trophic group abundance in differentiating habitats with a gradient of anthropogenic impact. Environ. Bioindicators 2, 146-160.
- Hoy, C. W., Grewal, P. S., Lawrence, J. L., Jagdale, G. and Acosta, N. 2007. Canonical correspondence analysis demonstrates unique soil conditions for entomopathogenic species compared with other free living nematodes. (pending)
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Progress 01/01/06 to 12/31/06
Outputs
This project involves novel ecological research to identify the habitat characteristics needed for persistence of entomopathogenic nematode populations in agroecosystems. We have found naturally occurring entomopathogenic nematode populations, species that are sold commercially as biological controls, in soils throughout a diversified vegetable production area in Ohio. Earlier in the project, we conducted a systematic survey for naturally occurring nematode populations in the Ohio vegetable production landscape. We took 100 soil samples from randomly selected locations in each of 6 habitat classes: forest, unmanaged shrub and meadow, grassy borders of vegetable fields, residential turf, agronomic row crops, and vegetable crops. Naturally occurring entomopathogenic nematodes have been confirmed in 43 of the samples, representing all but the vegetable crop habitats and with the greatest number of positive sites in minimally maintained grassy areas. Free-living nematodes
were extracted from each soil sample and identified to family and classified according to functional group. Measurements of soil chemical and physical and microbial biomass were taken for each sample by the OARDC soil analytical laboratory. Data on nematode species and environmental conditions have been analyzed by canonical correspondence analysis, specifically designed to estimate the relative importance of a number of environmental conditions in explaining variation in abundance or occurrence of multiple species at a number of sample sites. Approximately 80% of the variation in the species-environment relationship could be explained by the combination of environmental variables. The variables identified as being the most important in shifting from the vegetable field conditions to those present in the grassy borders were increased structure and enrichment in the soil food web, lower carbon:nitrogen ratios, increased K and decreased P. A subset of 144 sites was sampled monthly over
the 2005 and 2006 growing seasons for soil abiotic and biotic conditions, entomopathogenic nematode populations, and associated plant and insect communities over time. The nematode populations themselves fluctuate over time, as expected, but are more likely to remain at detectable levels where they have been detected previously. Apparent extinctions and recolonizations at particular sample sites suggest that metapopulation dynamics could provide a useful theoretical framework for the population dynamics of these biological control agents. Insect populations were generally more abundant in habitats where entomopathogenic nematodes were detected more frequently. Coleoptera and Hymenoptera were the most abundant orders in the grass-dominated habitats where nematodes were most frequently observed.
Impacts
Our research provides insight into how populations of non-pest alternative host insects for entomopathogenic nematodes might be managed. We found encouraging results in that the variables most important in providing good habitat for these biological controls of insect pests are the same variables that farmers control by the way they fertilize and till the soil. Non-pest insect hosts are needed to sustain their populations and we have gained insight into the community of soil dwelling insects that can serve this purpose.
Publications
- Stuart, R. J., M. E. Barbercheck, P. S. Grewal , R. A. J. Taylor , and C. W. Hoy. 2006. Population Biology of Entomopathogenic Nematodes: Concepts, Issues and Models. Biological Control. 38: 80-102.
- Lawrence, J. L., C. W. Hoy and P. Grewal. 2006. Spatial and temporal distribution of endemic entomopathogenic nematodes in a heterogeneous vegetable production landscape. Biological Control. 37: 247-255.
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Progress 01/01/05 to 12/31/05
Outputs
This project involves novel ecological research to identify the habitat characteristics needed for persistence of entomopathogenic nematode populations in agroecosystems. We have found naturally occurring entomopathogenic nematode populations, species that are sold commercially as biological controls, in soils throughout a diversified vegetable production area in Ohio. We found these nematodes in soils from the grassy borders surrounding fields, but not in the cropped area with the same soil type and just meters away from the grassy borders. We conducted a systematic survey for naturally occurring nematode populations in the Ohio vegetable production landscape. During October until December 2004, we conducted an initial intensive survey to determine the influence of a wide range of environmental factors that we hypothesize to be responsible for the difference in nematode occurrence between the grassy borders and vegetable fields. We took 100 soil samples from randomly
selected locations in each of 6 habitat classes: forest, unmanaged shrub and meadow, grassy borders of vegetable fields, residential turf, agronomic row crops, and vegetable crops. Naturally occurring entomopathogenic nematodes have been confirmed in 42 of the samples, representing all but the vegetable crop habitats and with the greatest number of positive sites in minimally maintained grassy areas. During 2005, free-living nematodes were extracted from each soil sample and identified to family and classified according to functional group. Measurements of soil chemical and physical and microbial biomass were taken for each sample by the OARDC soil analytical laboratory. Data on nematode species and environmental conditions have been analyzed by canonical correspondence analysis, specifically designed to estimate the relative importance of a number of environmental conditions in explaining variation in abundance or occurrence of multiple species at a number of sample sites.
Approximately 80% of the variation in the species-environment relationship could be explained by the combination of environmental variables. The variables identified as being the most important in shifting from the vegetable field conditions to those present in the grassy borders were increased structure and enrichment in the soil food web, lower carbon:nitrogen ratios, increased K and decreased P. A subset of 144 sites was selected based on the analysis results. This subset of sampling sites was observed monthly over the 2005 growing season, sampling for soil abiotic and biotic conditions and entomopathogenic nematode populations over time. Results of these data will determine how the conditions important to entomopathogenic nematodes fluctuate over time, and to what extent they are associated with the arthropods on which the nematodes feed.
Impacts
If combinations of environmental conditions that lead to persistence of entomopathogenic nematodes are known, then crop management practices ultimately could be designed to encourage persistence of these biological control agents and long-term pest suppression. We found encouraging results in that the variables most important in providing good habitat for these biological controls of insect pests are the same variables that farmers control by the way they fertilize and till the soil.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
This project involves novel ecological research to identify the habitat characteristics needed for persistence of entomopathogenic nematode populations in agroecosystems. If combinations of environmental conditions that lead to persistence of entomopathogenic nematodes are known, then crop management practices ultimately could be designed to encourage persistence of these biological control agents and long-term pest suppression. We have found naturally occurring entomopathogenic nematode populations, species that are sold commercially as biological controls, in soils throughout a diversified vegetable production area in Ohio. We found these nematodes in soils from the grassy borders surrounding fields, but not in the cropped area with the same soil type and just meters away from the grassy borders. The literature and our preliminary experiments suggest a number of environmental factors that we hypothesize to be responsible for the difference in nematode occurrence
between the grassy borders and vegetable fields. To determine how these factors influence entomopathogenic nematode persistence, individually and particularly in combination, we will conduct: 1) A systematic survey for naturally occurring nematode populations in the Ohio vegetable production landscape with sample sites chosen to achieve gradients in each of the hypothesized environmental conditions. Data on nematode species and environmental conditions will be analyzed by multivariate statistical techniques specifically designed to estimate the relative importance of a number of environmental conditions in explaining variation in abundance or occurrence of multiple species at a number of sample sites. 2) A manipulative experiment will be established to test the effect of various combinations of environmental conditions on persistence of a known initial population of entomopathogenic nematodes. The combined results of this research will provide needed ecological understanding of
entomopathogenic nematode population dynamics, how and where these species persist, and how they might be conserved in agroecosystems. During October to December 2004, we conducted the initial intensive survey, taking 100 soil samples in each of 6 landscape classes. Naturally occurring entomopathogenic nematodes have been confirmed in 36 of the samples, representing 5 of the 6 landscape classes but predominating in minimally maintained grassy areas. Faunal analysis of soil food webs, based on free-living nematodes extracted from each soil sample, is being conducted currently as are measurements of soil chemical, physical and biological properties. A subset of sites will be selected for detailed sampling of soil abiotic and biotic conditions and entomopathogenic nematode populations over time
Impacts
We expect this project to improve understanding of the ecology of entomopathogenic nematodes and enable an alternative approach to biological control of soil insect pests. By identifying the soil and habitat conditions that promote survival and reproduction, strategies to conserve these beneficial organisms can be explored.
Publications
- No publications reported this period
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