PLANT-PARASITIC NEMATODE MANAGEMENT AS A COMPONENT OF SUSTAINABLE SOIL HEALTH PROGRAMS IN HORTICULTURAL AND FIELD CROP PRODUCTION SYSTEMS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1012085
• Multistate No.: NE-1640
• Project Start Date: Jan 11, 2017
• Project End Date: Oct 1, 2021
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF VERMONT
(N/A)
BURLINGTON,VT 05405

Performing Department
Plant & Soil Science

Non Technical Summary
The concept of soil health uses certain characteristics such as low numbers of plant pests and pathogenic organisms, as well as high abundance of organisms that promote plant growth, such as the majority of non-pathogenic soil nematodes.Current concerns of global climate change, pollution and soil loss are prompting a renewed look at ecology of soil nematodes in arable soils for alternative and effective strategies in disease management and plant nutrition.In nematology, knowledge of plant-pathogenic nematodes of economic or quarantine importance is orders of magnitude greater than that of free-living or beneficial nematodes that comprise up to 60 to 80% of the community. Since 1988, the concept of nematodes as soil quality indicators and their predictive use in soil management represents a tremendous shift in emphasis in the discipline of nematology. Formerly, nematology was primarily a science focused on the management of parasitic and harmful plant pathogenic species. Currently, nematodes are also recognized as an integral and potentially useful component of soil systems.Soil disturbance, be it physical or chemical, can have numerous effects on the composition of soil invertebrate communities. For example, soil compaction reduces soil porosity, destructive to soil communities both destroying habitat and eliminating natural predators. Chemical disturbance including amendments for fertility, organic matter, and pesticides lead to a general enrichment phenomenon and favor the bacterial channel. A combination of cultivation and fertilizer reduce the flow through the fungal channel.Organic management often relies on intensive tillage to manage weeds, yet this practice may neutralize the biological benefits of organic amendments for fertility and pest management. Because soil organisms are difficult to see, farmers have little understanding of how management practices, such as tillage and cover crops, directly impact the composition and function of beneficial soil biota. The successional status of a soil community may reflect the history of disturbance. Less disturbance allows for soils to perform ecological functions of decomposition and nutrient cycling, which are desirable traits of healthy soil. Succession in cropped agricultural fields begins with depauperate soil after cultivation and clearing of unwanted vegetation that acts like an island to which organisms immigrate. First, opportunistic species, such as bacteria and their predators, are colonists of soil. Communities become dominated by organisms with short generation times, small body size, rapid dispersal and generalist feeding habits such as by bacteria and bacterivorous nematodes. Subsequently, fungi and fungivorous nematodes migrate into the area. Secondary and tertiary consumers or predators establish later. Indices of ecological succession are more reliable in detecting statistical differences than relative abundance or individual trophic groups. Different species exhibit contrasting levels of sensitivity or tolerance to disturbance because of unique survival and/or reproductive traits. For example, conventional tillage can reduce ratios of amoebae to flagellate protozoa and oribatid- to astigmatid mites. Two variations of these indices have been employed successfully for nematodes: Maturity index is a weighted mean of abundance of taxa at different states of ecological succession; channel and structural indices are subsets of the maturity index that reflect early and late succession, respectively. Ratio of fungivorous to bacterivorous nematodes similarly reflects the succession phase of decomposition. In both cases, smaller values reflect more recent or greater intensity disturbance. These measures are indicators of soil degradation.Additions of organic matter, such as compost, are considered beneficial for vegetable cropping systems because they contribute positively to promote plant growth, increase yield, and suppress disease. Compost research is among the top five research priorities identified by the Organic Farming Research Foundation. Composted organic wastes can serve as a biological inoculant for field soils to reduce the severity of root diseases. We know the microbiology differs among compost recipes and production processes but neither the ecological function nor mechanisms have been described for these microbial communities. With a better understanding of the microbiology of organic amendments, we can learn the pivotal points where it can be managed to enhance disease suppressiveness either by regulating the microbe-microbe interactions or microbe-plant interactions in soil.Biological indicators are underrepresented in programs designed to measure health of agricultural soil, e.g., Cornell Soil Health Assessment which has major impact and adoption in the northeastern US. While it provides useful information on the chemical and physical components of soil, it places little emphasis on soil biology; focusing solely on root health in terms of overall vigor and damage by root pathogens such as Fusarium, Pythium, or Rhizoctonia. Microbes and organic matter are the most commonly employed, but are difficult to interpret because of their spatial and temporal variation. Therefore, it makes more sense to move up the food chain to secondary, tertiary or quaternary consumers. They integrate all levels of food chain below and chemical/physical factors, and sometimes present top or keystone predators. Although chemistry and microbial biomass are correlated with nematode community indicators, they explain only 23% of variation of soil nematode community composition. Nematode community indices are useful tools to both assess the impact of agricultural management practices on nematode community structure dynamics and add to soil health toolkits calibrated by geographic region and specific agronomic and horticultural production systems. Interpretation requires a baseline database of these indices calibrated by ecoregion and ecosystem type. Initial efforts demonstrated the utility of successional based indices to quantify effects of cultivation, application of organic amendments, contamination by polycyclic aromatic hydrocarbons and heavy metals, maturation of compost, and establishment of biological soil crust. A long-term goal is to add a biological indicator representing beneficial soil invertebrates to the Cornell Soil Health Assessment. This adds a component that measures ecological function and environmental impact, which are interdependent with productivity to achieve sustainable intensive production systems.

Animal Health Component

40%

Research Effort Categories

Basic

60%

Applied

40%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
212	1499	1070	45%
215	1499	1040	30%
403	4099	1070	25%

Knowledge Area
212 - Pathogens and Nematodes Affecting Plants; 403 - Waste Disposal, Recycling, and Reuse; 215 - Biological Control of Pests Affecting Plants;

Subject Of Investigation
1499 - Vegetables, general/other; 4099 - Microorganisms, general/other;

Field Of Science
1040 - Molecular biology; 1070 - Ecology;

Keywords

disease suppression

organic amendments

soil health

Goals / Objectives
Determine the ecological interactions between nematode populations, nematode communities, ecosystems and soil health. Outreach and communication - Compile and present/ publish guidance on nematode management and management effects on soil health for different crops under different conditions.

Project Methods
1) Vermont will continue to evaluate the fungal and bacterial aspects of suppressive soils with the aim of narrowing in on mechanisms of natural suppression of SCN in collaboration with Minnesota. Composts of known recipe and process will be evaluated for mechanisms associated with suppression of disease. Composts provide a nutritious substrate and habitat to support beneficial microbes and predaceous invertebrates analogous to a probiotic for soil.3) Assist in obtaining funding for a GoTo Nematology Website to provide specific information on The Role of Plant-parasitic Nematodes and Nematode Management in Biologically Based Agriculture. Provide leadership to contribute a series on soil health and bio-based agricultural systems.

Progress 10/01/19 to 09/30/20

Outputs
Target Audience:Organic vegetable farmers that have limited tools to manage Rhizoctonia solani, an aggressive pathogen and a saprophyte that can survive as sclerotia between growing seasons. Bottom rot of lettuce, caused by R. solani, is a recurring problem for vegetable growers in Vermont, reducing field lettuce yields by 10-50%, and up to 80-90% for lettuce in over-wintered high tunnels (personal communication with organic vegetable growers in Vermont). It is a problem exacerbated by increasingly warm and wet fall conditions. Changes/Problems:The COVID-19 pandemic interrupted our experiments to identify anastomosis groups of Rhizoctonia solani isolates. Experiments are resumed thereby delaying results. What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?Plans for the next reporting period are to: 1) conduct the second and final year of on-farm field trials to manage Rhizoctonia solani in organic vetetable fields, 2) complete anastomosis group determinations for Vermont isolates of R. solani.

Impacts
What was accomplished under these goals? We completed the first of two years of replicated on-farm field experiments to evaluate two methods for reducing the inoculum load of Rhizoctonia solani in organic lettuce production fields: anaerobic soil disinfestation and blending vermicompost in starter mix.

Publications

• Type: Journal Articles Status: Published Year Published: 2020 Citation: Neher, D.A., Limoges, M.A., Weicht, T.R., Sharma, M., Miller, P.D. and Donnelly, C. 2020. Bacterial community dynamics distinguish poultry compost from dairy compost and unamended soils planted with spinach. Microorganisms 8(10):1601. doi:10.3390/microorganisms8101601
• Type: Book Chapters Status: Awaiting Publication Year Published: 2020 Citation: Neher, D.A. and Yeates, G.W. 2020. Moving up within the food web: Protozoa and nematodes. Chapter 15 in Uphoff, N. and Thies, J. Biological Approaches to Regenerative and Resilient Soil Systems, Second Edition. CRC.
• Type: Book Chapters Status: Awaiting Publication Year Published: 2020 Citation: Neher, D.A. and Hoitink, H.A. 2020. Compost use for plant disease suppression. Chapter 14 in: Rynk, R. On-Farm Composting Handbook, Second Edition.

Progress 10/01/18 to 09/30/19

Outputs
Target Audience:Organic vegetable farmers that have limited tools to manage Rhizoctonia solani, an aggressive pathogen and a saprophyte that can survive as sclerotia between growing seasons. Bottom rot of lettuce, caused by R. solani, is a recurring problem for vegetable growers in Vermont, reducing field lettuce yields by 10-50%, and up to 80-90% for lettuce in over-wintered high tunnels (personal communication with organic vegetable growers in Vermont). It is a problem exacerbated by increasingly warm and wet fall conditions. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?Anaerobic soil disinfestation will be tested in replicated on-farm trials. To our knowledge, the proposed study will be the first field test of ASD on soilborne pathogens of vegetables crops in the northeastern US.The experiment will use a randomized complete block design with four blocks at each of two farms. There is a history of bottom rot of lettuce identified by both grower and researcher in multiple fields at each farm. Each block will contain 1 plot of each treatment arranged randomly for a total of 32 samples per year (3 treatments + 1 control x 4 planting blocks x 2 farms). Plots will be a 3.05m (10') length of bed (containing 3 rows of plants, with 0.305 m (12") between plants, and 30 to 41 cm between rows.Treatments will include Vermont Compost Company compost (Montpelier, Vermont), Giroux composted poultry manure (Chazy, New York), and farm grown chopped winter rye all compared to an untreated control. The three amendment treatments were chosen, respectively, to represent the farmer's current practice, an increasingly popular amendment chosen for its low cost, and a common and inexpensive cover crop used in the region. Application rate will be calculated based on carbon content of each material with a target carbon application of 4 mg/ha. Carbon material will be incorporated to a depth of 10 to 25 cm with a rototiller followed by irrigation with 5 cm water. The area will be covered with a silage tarp and incubated three weeks. Soil moisture and temperature will be recorded hourly at 12 cm depth. Tarps will extend one bed width beyond treatment area to control for edge effect. Crop evaluation will be conducted in each of two successive years. For each plot, we will quantify disease incidence and severity at consistent crop phenology, after a post-treatment radish assay and July planting of lettuce.

Impacts
What was accomplished under these goals? We collected preliminary data from experiments using molasses as a labile carbon sourse in a controlled environment (phase 1) and a hoop house (phase 2). Phase 1 was conducted in 7.6 liter (2-gallon) re-sealable plastic bags in incubators at 32°C (89.6°F). Seed germination and seedling establishment of radish (indicator plant) after treating soil with a history of R. solani with molasses and an anaerobic environment for 27 days. Disease severity and incidence in ASD was less than treatments without molasses as a labile carbon source and/or aerobic conditions (p = 0.0114). In phase 2, we performed ASD in a commercial hoop house (280 sq meters, 3,000 sq ft) with a history of pre-emergence damping-off disease caused by R. solani. We mapped the spatial distribution of pre-emergence damping-off of radish as an indicator plant before and after the ASD treatment. Incidence of pre-emergence damping-off decreased substantially after ASD (p < 0.05). ASD soil had a slightly more diverse population of actinobacteria than the untreated soil. The actinobacteria in the ASD treatment suppressed growth of R. solani in a competition plate assay.

Publications

• Type: Journal Articles Status: Published Year Published: 2019 Citation: Hu, W., Kidane, E., Neher, D.A., and Chen, S. 2019. Field and greenhouse evaluations of soil suppressiveness to Heterodera glycines in the Midwest corn-soybean production systems. Journal of Nematology 51:e2019-32. doi.org/10.21307/jofnem-2019-032
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Neher, D.A., Nishanthan, T., Grabau, Z.J., and Chen, S.Y. 2019. Crop rotation and tillage affect nematode communities more than biocides in monoculture soybean. Applied Soil Ecology 140: 89-97. doi.org/10.1016/j.apsoil.2019.03.016
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Neher, D.A., Cutler, A.J., Weicht, T.R., Sharma, M., and Millner, P.D. 2019. Composts of poultry litter or dairy manure differentially affect survival of enteric bacteria in fields with spinach. Journal of Applied Microbiology 126:1910-1922. doi.org/10.1111/jam.14268
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Neher, D.A. Progress and priorities for nematodes as indicators. Invited symposium speaker, Organization of Nematologists of Tropical America, San Jose, Costa Rica, 21-25 July 2019.
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Neher, D.A. Nematodes: tail of ecosystem function. Voluntary oral presentation, Organization of Nematologists of Tropical America, San Jose, Costa Rica, 21-25 July 2019.
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Neher, D.A. Nematodes are bioindicators of soil function. Voluntary poster, Organization of Nematologists of Tropical America, San Jose, Costa Rica, 21-25 July 2019.
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Neher, D.A. Nematode communities as ecological indicators of ecosystem health. Brazilian Congress of Nematology, Caldas Novas, Goi�s, 26-30 May 2019. Invited speaker.

Progress 10/01/17 to 09/30/18

Outputs
Target Audience:Targeted two audiences, Soil Health Institute and Ecological Society of America. Neher, D.A. Nematodes are bioindicators of soil function. Soil Health Institute Third Annual Meeting, Albuquerque, NM, 26-28 July 2018 (poster presentation) Neher, D.A. Building a multi-decadal library on soil biology research, Soil Health Institute Third Annual Meeting, Albuquerque, NM, 26-28 July 2018. (poster presentation) Neher, D.A. Nematodes: The tail of ecosystem function in Integrating disciplines to assess global soil biodiversity, Ecological Society of America, New Orleans, 5-10 August 2018. (invited symposium speaker) Changes/Problems:1. We discovered that water holding capacity (potential for anoxia) became a problem in treatments amended with organic than inorganic fertility, especially in the poultry compost. We willadd peat to the inorganic fertilizer treatment next time to adjust for this unforeseen difference. 2. It is taking longer than expected to publish our results from 1) collaboration project that incorporates microbe of indigenous soil microbes and soil microclimate data into models to predict survival of E. coli in manure-based composts, and 2) microbial community dynamics in compost-amended soils and their effect on Escherichia coli survival. What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest?Opportunites arose to target two audiences, soil scientists attending the third conference of the Soil Health Institute (July 2018) and ecologists at the annual conference of Ecological Society of America (August 2018). Two posters were presented at the SHI meeting that provided educatoin on the past 25 years of reserach evaluating nematodes as biological indicators of soil. Nematodes was featured as one of six talks in a lightening talk format at a symposium on integrating disciplines to assess global soil biodiversity. What do you plan to do during the next reporting period to accomplish the goals?1. Conduct Phase 2 of greenhouse experiment to determine how addition of a soilborne pathogen, Rhizoctonia solani, affects overall plant growth and disease severity. The focus is on the community composition and communication of bacteria and fungi paritioned among the root, rhizoplane, and rhizosphere. We will sequence samples from Phase 1, and again from Phase 2 for comparison. 2. Conduct laboratory mesocosms to confirm the feeding preferences of Mesostigmatid mites, extracted from bedded pack alive. We will add two treatments to the yeast (Saccharomycetales) and Diptera fly larvae diets: nematode Panagrellus, and a mixture of yeast, nematode and fly larvae. 3. Initiate a new project USDA-NIFA-2018-51300-28561, Bedding strategies that promote udder health and milk quality by fostering a beneficial microbiome on organic dairy farms.

Impacts
What was accomplished under these goals? Three projects are at various stages of completion: Project 1. Last year, I reported that poultry-based compost maintained populations of Escherichia coli in contrast to dairy-based compost or without compost. My recent focus has been on understanding microbial mechanisms from a three-year field experiment conducted on two soil types. Although nitrogen availability (especially NH4) in poultry manure and litter, the bacterial and fungal communities also play a role. From microbial ecoenzyme assays, we learned that microbial communities were universally carbon limited across all treatments. After application of compost, microbial communities exhibited N deficiency initially and then shifted to more P deficient after 14 epi. This change after treatment was applied demonstrates that compost provides sufficient nutrients for E. coli growth but was limited in carbon throughout the experiment. Composition of bacterial and fungal communities in Poultry litter compost treatments contrasted those of dairy compost and no compost controls. Poultry compost treatments contained more bacteria of the phyla WS3, Actinobacteria, Fibrobacteres and Plantocycetes than dairy composts or the control without compost. All fungal OTUs were relatively less abundant in poultry than dairy or no compost treatments. Our results are consistent with studies conducted in other regions of the US, suggesting that poultry litter-based amendments support greater numbers and longer periods of persistence in field soils of E. coli than dairy-manure based compost. Project 2. We completed an in-depth single farm study that surveyed bedded pack (microbiome and microarthropod community), dipteran vectors of bacterial mastitis pathogens, and the teat skin and teat cistern milk microbiomes. Comparisons were made with four additional farms utilizing bedded packs to test generality of results. Bedding on all farms was found to harbor the mesostigmatid mite genus Glyptholaspis, a well-established predator of nematodes and muscid fly larvae, suggesting that predators may suppress populations of biting flies in bedded pack barns. Additionally, the fungivorous genus Rhizoglyphus was commonly abundant in all farms, suggesting that the mite community regulates microbial activity at multiple trophic levels. High-throughput sequencing of universal marker genes for bacterial and fungal communities to characterize the skin and milk microbiome of cows with both a healthy and infected quarter on the case study farm, and the composted bedded pack of all five farms. The bedded pack microbiome varied with bedding material and management style; fungal taxa were primarily yeasts of the Ascomycota; all farms additionally contained anaerobic fungi associated with the bovine rumen. Common bacterial genera included Acinetobacter and Pseudomonas, both of which were also commonly observed on teat skin and in milk. Results support an ecological interpretation of both the udder and the bedded pack environment and support the notion that mastitis can be described as an imbalance of the healthy mammary gland microbiome. Project 3. We partially completed our goal of evaluating vermicompost and poultry pellets on root growth and disease severity with and without Rhizoctonia solani. Methods development took much longer than anticipated. We completed phase 1, the effect of three compost types on growth tomato plants without the pathogen, but not phase 2, adding R. solani to the system. A greenhouse trial with four treatments was replicated three times. Tomato growth was compared in four soil amendments (control with inorganic fertilizer, dairy windrow compost, dairy-based vermicompost compost, and poultry litter compost), standardized by total nitrogen availability. Plant growth was greater with vermicompost than dairy windrow or poultry litter composts. We collected root, rhizoplane and rhizophere samples at four phenological stages (seedling, early vegetative, late vegetative, early flowering). These samples were exposed to propidium monoazide to degrade relic DNA and then frozen at -80 C. These samples will be sequenced to compare bacterial and fungal communities across root partitions to gain insight into rhizosphere mechanisms that suppression soilborne pathogens and disease establishment.

Publications

• Type: Journal Articles Status: Published Year Published: 2018 Citation: Steel, H., Moens, T., Vandecasteele, B., Hendrickx, F., De Neve, S., Neher, D. A., and Bert, W. 2018. Factors influencing the nematode community during composting and nematode-based criteria for compost maturity. Ecological Indicators 85: 409-421. DOI 10.1016/j.ecolind.2017.10.039.
• Type: Journal Articles Status: Awaiting Publication Year Published: 2018 Citation: Neher, D.A., Weicht, T.R. 2018. A plate competition assay as a quick preliminary assessment of disease suppression. Journal of Visualized Experiments e58767, doi:10.3791/58767.
• Type: Conference Papers and Presentations Status: Other Year Published: 2018 Citation: Neher, D.A. Nishanthan, T., Grabau, Z., and Chen, S. Foodweb indicators of soils naturally suppressive to soybean cyst nematode. Invited symposium speaker, Organization of Nematologists of Tropical America, Arequipa, Peru, 19-23 August 2018.
• Type: Conference Papers and Presentations Status: Other Year Published: 2018 Citation: Neher, D.A. Nematodes: The tail of ecosystem function in Integrating disciplines to assess global soil biodiversity. Invited symposium speaker, Ecological Society of America, New Orleans, LA, 5-10 August 2018.
• Type: Conference Papers and Presentations Status: Other Year Published: 2018 Citation: Neher, D.A. Nematodes are bioindicators of soil function. Poster at Soil Health Institute Third Annual Meeting, Albuquerque, NM, 25-27 July 2018.
• Type: Conference Papers and Presentations Status: Other Year Published: 2018 Citation: Neher, D.A. Building a multi-decadal library on soil biology research, Poster at Soil Health Institute Third Annual Meeting, Albuquerque, NM, 25-27 July 2018.
• Type: Conference Papers and Presentations Status: Other Year Published: 2018 Citation: Bradshaw, R., Shah, M. K., Handy, E. T., East, C., Nyarko, E., Millner, P. D., Neher, D., Weicht, T., Bergholz, T. M., Sharma, M. Survival and growth of Salmonella Newport in amended and unamended soil extracts. International Association for Food Protection, July 2018.
• Type: Conference Papers and Presentations Status: Other Year Published: 2017 Citation: Andrews, T., Neher, D. A., Weicht, T. R., and Barlow, J. Linkages between bedded pack and healthy and mastitic cow udder microbiomes. Argonne Soil Metagenomics Meeting, 1-3 November 2017.

Progress 01/11/17 to 09/30/17

Outputs
Target Audience: Nothing Reported Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest?Presentations Neher, D.A. Soil health - What progress have we made in the past 25 years? Invited presentation. Soil Ecology Society, Ft. Collins, Colorado, June 5-9, 2017. LeDuc, M., Andrews, T., Weicht, T.R., and Neher, D.A. Microarthropods in bedded pack: A source for biocontrol of biting fly pests on dairy farms? Contributed oral presentation. Soil Ecology Society, Ft. Collins, Colorado, June 5-9, 2017. Andrews, T., Neher, D. A., and Weicht, T. R. Microbial ecology of composting bedded pack, 2017. Contributed poster. Soil Ecology Society, Ft. Collins, Colorado, June 5-9, 2017. Limoges, M., Neher, D.A., Weicht, T.R., Millner, P.D., Sharma, M., and Donnelly, C. Survival of generic E. coli and Listeria spp. populations in dairy compost- and poultry litter compost-amended soils in the northeastern U.S. International Association for Food Protection, 2017. Lekkas, P., Sharma, M., Neher, D.A., Weicht, T.R., Millner, P., and Donnelly, C. The effect of soil management on the persistence of E. coli and Listeria spp. in manure- amended soils in the Northeast United States. International Association for Food Protection, 2017. What do you plan to do during the next reporting period to accomplish the goals? Incorporate microbiome of indigenous soil microbes and soil microclimate data into models to predict survival of E. coli in manure-based composts. Evaluate vermicompost and poultry pellets effect on root growth and disease severity with and without Rhizoctonia isolated from local fields in a replicated greenhouse bioassay and using metagenomics of bacteria/archaea and fungi in root, rhizosphere, and bulk soil. In laboratory mesocosms, confirm that Mesostigmatid mites, extracted from the pack live, will feed on yeast fungi in the Saccharomycetales and Diptera fly larvae. Given their biological niche, their presence in the bedded pack material, and their apparent proximity to the fly larvae, they may have potential as a biological control agent.

Impacts
What was accomplished under these goals? Goal 1. We completed a third year of a field study on the persistence of enteric pathogens in manure-amended soils in northeast U.S. produce-growing environments. There was negligible Escherichia coli survival by 80 days. Decline of E. coli was faster at surfaces of untilled plots than at 10 cm depth in tilled soils. Over-wintering in Vermont was sufficient to insure no carryover of E. coli applications from applications in the prior fall to spring. These data will be used to inform the Food Safety and Modernization Act. We completed a second year of a field experiment on the ecological dynamics in compost-amended soils and the resulting effects on E. coli survival. Poultry litter-compost support greater numbers and longer periods of persistence in field soils of E. coli than dairy-based composts. We are analyzing ancillary data related to community composition of indigenous bacterial and fungal communities, and ecoenzymes to quantify the function of nutrient acquisition. Bedded pack management for fly control reduces mastitis risk for organic cow dairies. Bedded pack supported greater relative abundance of bacterial taxa associated with healthy-milk compared to mastitis associated. Pseudomonas spp. were associated with the healthy microbiome while P. viridiflava was associated with the mastitic microbiome. Mesostigmata (Acari) mites were dominant within the microarthropod communities extracted from bedded pack. In laboratory mesocosms, we confirmed that Mesostigmatid mites, extracted from the pack live, will feed on yeast fungi in the Saccharomycetales and Diptera fly larvae. Given their biological niche, their presence in the bedded pack material, and their apparent proximity to the fly larvae, they may have potential as a biological control agent. Rhizoctonia solani accounts for losses of 30-50% in field-grown lettuce by organic vegetable farmers in Vermont annually, without prospect of control. We collected five virulent isolates from local fields and developed methods for greenhouse plant bioassays to evaluate vermicompost and poultry pellets effect on root growth and disease severity with and without R. solani. We plan to use metagenomics to compare communities of bacteria/archaea and fungi in roots, rhizosphere, and bulk soil within these mesocosms conducted in the coming year. Goal 2: nothing to report

Publications

• Type: Journal Articles Status: Published Year Published: 2017 Citation: Bakelaar, J.E., Neher, D.A., and Gilker, R. 2016. Minimal soil impact by cold season pasture management in Vermont. Canadian Journal of Soil Science DOI 10.1139/CJSS-2014-0005
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Neher, D. A., Fang, L., and Weicht, T. R. 2017. Ecoenzymes as indicators of compost to suppress Rhizoctonia solani. Compost Science and Utilization