Interactions between predators and insect-parasitic nematodes in soil

Final Report for GS00-004

Project Type: Graduate Student
Funds awarded in 2000: $10,000.00
Projected End Date: 12/31/2003
Region: Southern
State: North Carolina
Graduate Student:
Major Professor:
Mary Barbercheck
North Carolina State University
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Project Information

Summary:

In this research we are evaluating the interactions between various types of soil fauna and insect-parasitic (beneficial) nematodes used for biological control of soil-dwelling pests. Potential responses include predation impacts on (augmented or applied) nematode populations, or non-target effects of beneficial nematodes on the soil (“decomposer”) community.
Three strains of beneficial nematodes were applied inundatively, simulating commercial application, and via infected insect cadavers, simulating natural infection, in both conventional-till and no-till corn.
Data indicate that soil fauna responses to nematode application, both inundatively and via natural infection, are most evident at the level of individual taxa, rather than at the level of abundance and diversity. Differences in abundance and diversity of particular groups of soil fauna due to tillage (higher in no-till than conventional-till) and to time (higher at 24 hours than at 4 hours) were also detected.
(GSA-21)

Introduction

In an agricultural setting the soil community plays a critical role in decomposition, nutrient cycling and the control of pathogens and pests of crops. Conservation and augmentation of soil-dwelling predators and pathogens may enhance the control of agricultural pests. The purpose of this research is to examine the response of soil fauna to an applied biological control agent; insect-parasitic nematodes.
Insect-parasitic nematodes in the families Steinernematidae and Heterorhabditidae occur naturally in the soil and are also applied inundatively, like a pesticide, at the commercial rate of 2.5 billion/hectare. In field applications, recovery of nematodes directly following application may yield less than 50%. This has generally been attributed to abiotic factors. Biotic factors, however, may also impact applied or augmented nematode populations.

Project Objectives:

The objectives of this research were to:
1) Evaluate the response of soil fauna to native and introduced insect-parasitic nematodes applied inundatively or via an insect cadaver, simulating a natural infection.
2) Evaluate the effects of tillage on the soil fauna response.
3) Evaluate the effects of time on the soil fauna response

Cooperators

Click linked name(s) to expand
  • C. Marie Greenwood

Research

Materials and methods:

Three strains of nematodes were used; one non-native commercial strain, Steinernema riobrave; and two nematodes native to the site, Steinernema carpocapsae, and Heterorhabditis bacteriophora.
To simulate a natural infection, Greater wax moth larvae (Galleria mellonella) were innoculated with individual strains of nematodes, producing infected insect cadavers. Cadavers were placed in cages (biopsy cassettes) approximately 2 days prior to nematode emergence and buried in the soil.
Nematodes applied inundatively were reared in the lab and collected within 2 days of application date. They were diluted in water at the commercial rate of 2.5 billion per hectare.
Both inundative applications and cadavers were placed in conventional-till and no-till corn in a complete randomized block design.
At 4 hours and 24 hours after nematode application soil samples were collected and soil fauna extracted, enumerated and identified. Physical soil data was collected concurrently with microarthropod soil samples.
Add data were analyzed using SAS PROC GLM.

Research results and discussion:

Collections included approximately 90,000 individuals belonging to145 soil invertebrate taxa which occurred in patchy distribution and variable abundance. Data indicated a higher diversity and abundance of soil fauna in the no-till versus conventional-till soil. Diversity and abundance of some groups of soil fauna also increased from 4 hours to 24 hours. Responses of soil fauna to the nematode treatments were not evident at the level of community abundance or diversity. Responses to nematode treatments, however, were evident at the level of community composition. Specific taxa of soil fauna responded, both positively and negatively, to treatments containing either nematodes in solution, or the nematode-bacteria-exudate complex represented within the insect cadaver treatments.
Key taxa of soil mites, including members of the Cunaxidae (Acari: Prostigmata), Histiostomatidae (Acari: Astigmata), Sancassania sp. (Astigmata: Acaridae) and several families of both Oribatid and Mesostigmatid mites, were also found to exhibit particularly strong responses to the presence of nematodes. Sancassania sp. occurred in particularly large numbers and were also observed to feed on nematodes in lab assays.
Extensive and detailed summaries of specific interactions between groups of soil invertebrates and entomopathogenic nematodes are presented in the PhD dissertation entitled: Interactions between soil invertebrates and entomopathogenic nematodes by C. Marie Greenwood, Department of Entomology, North Carolina State University, available June 18, 2004.

Participation Summary

Educational & Outreach Activities

Participation Summary

Education/outreach description:

Publications are pending. Four publications are currently planned resulting from chapters of C. Marie Greenwood’s dissertation; projected finish date of June 18, 2004.
Numerous outreach presentations have involved data resulting from this project (as listed in the “impact” section):
Numerous presentations regarding this project have also been made at grower meetings, agriculture-related classes, professional meetings and soils workshops conducted at the Center for Environmental Farming Systems (CEFS) near Goldsboro, NC., as well as in the Raleigh area (see below). The results of this project will be used as an integral component of a PhD dissertation entitled: Interactions between soil invertebrates and entomopathogenic nematodes by C. Marie Greenwood, Department of Entomology, North Carolina State University, which will be available June 18, 2004. Chapters from this dissertation will also be submitted for publication in professional journals specializing in soil ecology interactions and sustainable agriculture.

1. Invited presentation for the NRCS Pastureland Ecology course at North Carolina State University. May 17-27, 2004
2. Poster presentation (student competition) for Entomological Society of America annual meeting; Oct 23-25, 2004; Cincinnati, Ohio
3. Invited presentation for SSC 210 Soil Science at Chatham County Community College; provided lecture on Introduction to Soil fauna; September, 2003.
4. Invited presentation for SSC (Soil Science) 620 Soil Ecology; North Carolina State University; provided lecture on Introduction to Soil Fauna/research methods; Sep, 2003.
5. Bugfest 2003; Natural Science museum, Raleigh, North Carolina; established the “Living Soil” exhibit; August, 2003
6. Invited presentation for the Sustainable Agriculture Internship Program; Center for Environmental Farming Systems (CEFS), Goldsboro, NC; Soil Ecology workshop; June, 2002.
7. Invited presentation at the Center for Environmental Farming Systems Open House, July 2001
8. Invited presentation and lab exercise on soil microarthropods and predation at the Center for Environmental Farming Systems (CEFS) Sustainable agriculture internship program. July 26, 2000.
9. Pests and Beneficial Organisms. Invited presentation. SARE PDP Soil Management Train -the -Trainer Workshop, Raleigh, NC. September 22-24, 1999.

Project Outcomes

Project outcomes:

Numerous presentations regarding this project have also been made at grower meetings, agriculture-related classes, professional meetings and soils workshops conducted at the Center for Environmental Farming Systems (CEFS) near Goldsboro, NC., as well as in the Raleigh area (see below). The results of this project will be used as an integral component of a PhD dissertation entitled: Interactions between soil invertebrates and entomopathogenic nematodes by C. Marie Greenwood, Department of Entomology, North Carolina State University, which will be available June 18, 2004. Chapters from this dissertation will also be submitted for publication in professional journals specializing in soil ecology interactions and sustainable agriculture.

1. Invited presentation for the NRCS Pastureland Ecology course at North Carolina State University. May 17-27, 2004
2. Poster presentation (student competition) for Entomological Society of America annual meeting; Oct 23-25, 2004; Cincinnati, Ohio
3. Invited presentation for SSC 210 Soil Science at Chatham County Community College; provided lecture on Introduction to Soil fauna; September, 2003.
4. Invited presentation for SSC (Soil Science) 620 Soil Ecology; North Carolina State University; provided lecture on Introduction to Soil Fauna/research methods; Sep, 2003.
5. Bugfest 2003; Natural Science museum, Raleigh, North Carolina; established the “Living Soil” exhibit; August, 2003
6. Invited presentation for the Sustainable Agriculture Internship Program; Center for Environmental Farming Systems (CEFS), Goldsboro, NC; Soil Ecology workshop; June, 2002.
7. Invited presentation at the Center for Environmental Farming Systems Open House, July 2001
8. Invited presentation and lab exercise on soil microarthropods and predation at the Center for Environmental Farming Systems (CEFS) Sustainable agriculture internship program. July 26, 2000.
9. Pests and Beneficial Organisms. Invited presentation. SARE PDP Soil Management Train -the -Trainer Workshop, Raleigh, NC. September 22-24, 1999.

Recommendations:

Areas needing additional study

Further analyses, including repetition of experiments, are required to more accurately assess responses of specific taxa and how these responses may impact applied or augmented insect-parasitic nematode populations. This data will provide basic information regarding soil fauna interactions relative to application and augmentation of insect-parasitic nematodes in different tillage regimes over time that is essential in developing holistic sustainable methods of pest management in agriculture.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.