Enhance Tennessee's nursery and ornamental plant industry

Research to keep a major Tennessee industry strong


Sustainable Management of Arthropod Pests in Ornamental Nursery Production

Development of Sustainable Soilborne Disease Management Strategies for Nursery Production

Ecological and Genetic Diversity of Soil-borne Pathogens and the Soil Microbiome

Evaluation of Plant Endophytes as Biological Control Agents for Plant Diseases

Invasive and Key Insect Pest Management in Nursery Cropping Systems

Improving Profitability and Reducing Pesticide Use in Nursery Crop Production

Sustainable Management of Arthropod Pests in Ornamental Nursery Production
 Dr. Karla Addesso
The most recent comprehensive evaluation of the United States environmental horticulture industry reported economic contributions of $147.8 billion in output, 1,964,339 jobs, $95.1 billion in value added, $64.3 billion in labor income, and $6.9 billion in indirect business taxes (Hall et al. 2005). In Tennessee, nursery crops account for 10% of agricultural production with 570 farms contributing nearly $300 million to the state's annual economy (Tennessee Department of Agriculture 2011), approximately $132 million of that value in direct sales (2012 Census of Agriculture). As in other areas of agriculture, insect pest management programs are crucial to the production of healthy nursery stock, but despite the industry's considerable contribution to the United States economy, research on nursery crop pests lags behind in effort and funding focused on vegetables and row crops. The complex nature of the nursery industry due to the large number of plant species grown in individual nurseries is part of what makes nursery pest management research challenging. As such, pests that have large economic impacts, attack multiple, high production genera and are quarantine restricted are important targets for research. Integrated pest management (IPM) programs that incorporate host plant resistance, cultural, behavioral and chemical controls are more sustainable than programs focusing on only one of these techniques. A key element in developing successful IPM programs is a thorough understanding of insect behavior and chemical ecology. By understanding pest behaviors and identifying the chemicals influencing those behaviors, pest managers can target pests at vulnerable stages in their life cycle and manipulate pest populations so they can be more effectively controlled. In 2009, the Southern Nursery Integrated Pest Management Working Group established the Pest Management Strategic Plan for Container and Field-Produced Nursery Crops. They listed the following research priorities for the nursery industries in the region: (1) making IPM profitable and viable for nursery crop production, (2) investigating whole systems approaches to pest management and (3) development of conservation biological control tactics, such as habitat manipulation with flowering plants, to increase the abundance, diversity, and efficacy of naturally occurring predators and parasitoids. To support these strategic goals, the Chemical Ecology lab will focus resources on the study of arthropod pests that impact a wide range of high value woody ornamental crops. These pests may include spider mites, scales, wood borers, fire ants and other pests each of which affect a wide range of trees and shrubs. We will use behavioral studies of insects on which to base our experimental designs and management methods.

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Development of Sustainable Soilborne Disease Management Strategies for Nursery Production
 Dr. Fulya Baysal-Gurel
Nursery crops are produced with annual sale value of $5.1 billion in the United States. Nursery crops in Tennessee account for asignificant portion of agricultural production with $132 million in sales annually. Soilborne pathogens often survive for long periods on host plant debris, soil organic matter, or as free-living organisms. As an example, losses due to soilborne diseases in Georgia in 2014 were estimated to be $149 million in ornamental and turf production. Due to the large number of plant species produced in the nursery industry, soilborne disease management research is challenging. Nursery producers and university representatives at the Southern Region Nursery Crop Pest Management Meeting rated root rot as the most important disease in nursery production. In addition, based on nursery inspections and disease samples received in the Ornamental Plant Pathology Lab at the Tennessee State University Nursery Research Center (TSUNRC), we have documented that soilborne pathogens are the most economically important pathogens.These diseases reduced plant growth, increased costs to the nursery grower and caused potential ecological damage to the natural environment. The National Integrated Pest Management (IPM) Road Map has listed "Develop advanced management tactics for specific settings that prevent or avoid pest/disease attack" and efforts to "Improve the efficiency of suppression tactics and demonstrate least-cost options and pest/disease management alternatives" as critical research needs. Soilborne diseases are becoming more difficult to manage because of increased pathogen resistance and restrictions of the use of some chemicals. Conventionally, soilborne diseases are controlled by using soil fumigants, in-furrow fungicides, or fungicide seed treatment. Once a widely used fumigant, methyl bromide, was phased out of use in 2005 due to its negative effect on the stratospheric ozone layer. The loss of methyl bromide has promoted increased interest in alternative methods to control soilborne diseases. Although environmentally friendly chemical and non-chemical plant disease management methods have been developed, their results are still inconsistent and less effective than the previous standard, methyl bromide. Locally, large- and small-scale nursery producers have asked we develop and validate effective alternative soilborne disease management strategies to improve woody ornamentals productivity and profitability under particular environmental conditions. Several producers have participated in the development of this proposal by group discussion at the TSUNRC. The loss of methyl bromide has promoted increased interest in alternative environmental friendly methods to control soilborne diseases. The integration of biofumigation, chemical and biorational products solely, or in combination, will provide more successful and sustainable solutions for improving soil quality and enhancing natural soilborne disease control in field grown production and propagation systems of woody ornamentals. Therefore, we propose to encourage the adoption of proven uses of biofumigation, chemical and biorational products by documenting their effects in field grown nursery production and propogation systems. We emphasize that the development of a multiple systems approach to improve soilborne disease management and soil quality using biofumigation, chemical and biorational products will help improve the productivity, profitability and sustainability of field grown nursery production and propagation of woody ornamentals. The long-term goal of the proposed project is to improve production efficiency and reduce soilborne disease pressure through economic and effective applications of biofumigation, chemical and biorational products on field grown ornamental nurseries. Biofumigation, chemical and biorational products will be evaluated in field grown nursery production systems and their effects on plants, microbial communities, and soilborne diseases will be documented. In order to provide effective and sustainable recommendations to nursery producers with a useful synthesis of our results, the following objectives will be pursued: 1) assess environmentally friendly biofumigants in combination with solarization for soilborne diseases and improved plant growth; 2) assess the efficacy of chemical and biorational products for controlling soilborne diseases with different application methods, intervals and reduced-rate applications in woody ornamentals; and 3) engage in outreach and technology transfer with field nursery producers.

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Ecological and Genetic Diversity of Soil-borne Pathogens and the Soil Microbiome
 Dr. Fulya Baysal-Gurel
Agricultural and horticultural crops are produced with an estimated market value of $212.3 billion in the United States each year. Soil-borne plant pathogens are diverse and encompass microorganisms such as fungi, oomycetes, bacteria, viruses and nematodes that cause pre- and post-emergence damping-off, root and crown rots, vascular wilts, as well as foliar blight in these crops and amenity plantings. Soil-borne pathogens often survive for long periods on host plant residue, soil organic matter, or as free-living organisms. Soil-borne pathogens may have broad host ranges, and crop species may be susceptible to several different pathogens. Due to the menagerie of plant species produced by growers, and hectares managed, soil-borne disease management is challenging. Interactions with soil texture, chemistry, and environmental conditions make soilborne disease management challenging. The National Integrated Pest Management (IPM) Road Map has listed "Develop advanced management tactics for specific settings that prevent or avoid pest/disease attack" and efforts to "Improve the efficiency of suppression tactics and demonstrate least-cost options and pest/disease management alternatives" as critical research needs. Soil-borne diseases are becoming more difficult to manage because of increased pathogen resistance and restrictions of the use of some chemicals. Conventionally, soil-borne diseases are controlled by using soil fumigants, in-furrow fungicides, or fungicide seed treatment. Once a widely used fumigant, methyl bromide, was phased out of use in 2005 due to its negative effect on the stratospheric ozone layer. The loss of methyl bromide has promoted increased interest in alternative methods to control soil-borne diseases. Some soil-borne pathogens have broad host ranges, reducing the effectiveness of crop rotations in soil-borne disease management. Clearly, additional soil-borne disease management strategies suited to the practice of sustainable production are urgently needed. Over the last 15 years there have been surprising and exciting innovative discoveries for natural methods to suppress or eliminate plant pathogens, and/or protect crop plants. Intensive studies of disease-suppressive soils have led to the development of new methods of analysis and new insights into the nature of soil-borne disease suppression. Such advances indicate that active management of soil microbial communities can be an effective approach to developing natural suppression of diseases and improve crop productivity. This involves adjusting the types and timing of organic inputs, such as cover crops, animal manures, composts, compost teas, and crop sequencing. Such approaches have been shown to provide site-specific reductions in disease incidence. This technology fits the general requirements of sustainable agriculture in that it utilizes natural means to control diseases. However, standardized and reliable techniques for pathogen suppression have not been developed and widely tested on different crop production systems for controlling soil-borne diseases. In part, this is due to the wide variety of organic amendments that are available and their variable effects depending on the chemical makeup of organic substrates, soil types, and/or local climatic conditions. Soil incorporation of Brassica or other cover crops has the ability to suppress soil microorganisms through the hydrolysis of glucosinolates (GSL) into isothiocyanate, a natural biofumigant. GSL content and concentration differs among Brassica cultivars, the development stage of the plant, and the end product formed by hydrolysis of the GSL, so that different Brassicacultivars may have different levels of potential to control pathogens. Therefore, it is important to study the different GSL-hydrolyzed end products produced by different Brassica crops and their effect on major soil-borne diseases. Incorporation of biofumigant use in the crop production cycle may provide additional successful and sustainable solutions for improving soil quality and enhancing natural soil-borne disease control. The effective use of biofumigants in crop production appears to be limited by a range of factors, which needs to be examined to provide effective recommendations to growers. Several commercially available biopesticides are composed of specific isolates of soil microorganisms that were selected for their capacity to suppress a range of pathogens. These biopesticides may operate through multiple mechanisms, such as niche exclusion, biocidal/biostatic effects, antibiosis, predation, and parasitism. Some of the most common microbe-based biopesticides contain bacterial isolates of Bacillus spp., Pseudomonas spp., or Streptomyces spp., or fungal isolates of Gliocladium spp. or Trichoderma spp. Many of these organisms suppress disease and associated pathogen populations through multiple mechanisms. Numerous studies and reviews have documented the potential of microbe-based biopesticides to suppress both foliar and root diseases. However, the general consensus among these reviews is that integration is the key to obtaining consistent activity from biopesticides. Adoption of biopesticides has increased. But there is a need for biopesticides to provide workable disease management solutions for growers. Demand for biopesticides has continued to expand dramatically in the last 15 years. However, despite substantial growth in the industry and markets, there is still a lack of publicly available data that substantiates efficacy and return on investment for most products. There is a critical need to develop and disseminate science-based informational resources that will promote useful and sustainable adoption by growers that experience significant plant disease pressure. Given the need for sound integrated pest management, approaches coordinating chemical and biological controls are needed. Recently emphasis has been placed on understanding the phytobiome of plants or microbiome of production soils. While metagenomic techniques, in theory, should allow for identification and association with soil-borne diseases, more importantly, these techniques offer the opportunity to understand biological suppressiveness. However, there are limitations to these methods so evidence must be combined with spatial analysis or analyzed across multiple locations and years to limit sampling error and bias. Recently, the use of indigenous vs. synthetic microbiomes to control soil-borne diseases was explored. There are clear advantages with respect to survival and likely efficacy when microorganisms adapted to the specific environment or competing for a similar niche in the phytobiome are used. The long-term goals of the proposed project are to investigate the impact of rhizosphere microbial communities on plant health and on the productivity of diverse cropping systems, and to validate and evaluate different soil-borne disease management strategies under different environmental conditions.  

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Evaluation of Plant Endophytes as Biological Control Agents for Plant Diseases
 Dr. Margaret Mmbaga
Plant pathogens impose major constraints on agricultural production systems and cause huge losses in crop yields. Persistent challenges in using conventional fungicides to control plant diseases include toxicity hazards to humans, non-target beneficial organisms, environmental contaminations and development of fungicide resistance that render some fungicides ineffective. Although disease resistance is the preferred disease management strategy and is eco-friendly, it takes a long time and it is difficult to breed resistant cultivars for all plant- pathogen combinations in agricultural production systems. Besides, pathogens have the ability to evolve and impede their host plant defense mechanisms resulting in resistance breakdown. There is clearly a need to increase the diversity of eco-friendly products that are effective in disease management and are safe to human health, non-target organisms and environmental quality. Using microorganisms as biological control agents for plant disease is an attractive eco-friendly strategy for combating plant diseases. Microorganisms that colonize the internal tissues of plants without causing any external symptoms are called endophytes; they colonize the same tissue as disease-causing organisms. They are ubiquitous and have potential to provide valuable natural resource for plant disease management. Research on endophytes have shown that they form mutually beneficial associations with their host plants and play roles essential in plant survival such as inducing plant defense mechanisms, and reducing disease severity by different mechanisms, promoting plant growth by fixing atmospheric nitrogen and increase mineral nutrient uptake. Our previous studies have identified some endophytes that are antagonistic on various pathogens of agricultural importance. Such organisms may provide a resource for managing plant pathogens and reducing crop losses. However, the success in using microorganism as biological control agents for plant disease management is often dependent on the ability of the microorganisms to colonize the host plant tissues and the ability of the microorganisms to survive and function in plant protection under field environment. This project will address the following objectives: (1) Evaluate selected endophytes for host range, mechanism for introducing them into host plants and confirm previous results in greenhouse and field environments; (2) determine their plant growth-promoting ability, (3) assess the effect of soil ecological factors on plant colonization and on effectiveness of the selected microorganisms, and (4) evaluate how the selected organisms function as a population of more than one microorganism and their compatibility with fungicides as part of integrated disease management that combine different methods.

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Invasive and Key Insect Pest Management in Nursery Cropping Systems
 Dr. Jason Oliver
The U.S. green industry (nursery, greenhouse, turf, and other ornamental products) is an important contributor of employment in many rural and underdeveloped communities. The green industry accounted for 0.72% of U.S. Gross Domestic Product (GDP) and 1.11% of total workforce employment (~2.04 million jobs) during 2013 with a value addition to GDP of $120.7 billion ($82.5 billion being employee income. Greenhouse and nursery crops contribute $6.4 billion to the Tennessee economy. A 2017 green industry survey identified 3 top grower concerns as 1) state of the economy, 2) rising production costs, and 3) labor, while researchers identified key issues of 1) insects and diseases, 2) availability of water, and 3) government regulation. Unfortunately, invasive insects are a primary factor in rising production costs and government regulation. Multiple new nonindigenous insect pests and diseases have added significantly to the cost of producing nursery and greenhouse crops. These exotic species require frequent chemical inputs that increase cost, environmental contamination, worker exposure hazards, and cause secondary pest outbreaks. Species under federal and state quarantines hinder trade flow, and mandatory certification treatments increase costs and compromise sustainable integrated pest management programs. The focus group of the Southern Nursery IPM (SNIPM) Working Group's Pest Management Strategic Plan (PMSP) identified 21 key arthropods as management priorities in 2014. Insects on the priority list included mites, scale insects, imported fire ant (IFA), Japanese beetle (JB), wood borers (granulate ambrosia beetle and flatheaded borer), and various others. Many of these pests have high fecundity rates, ability to avoid pesticide treatments, life cycles that increase the risk of their transport in agricultural products (e.g., soil dwelling), or the ability to kill or damage marketability of host plants (e.g., borers). For many invasive insects, treatment options are limited, expensive, or not environmental sound. The proposed project addresses better management of key insect pests that are prevalent and re-occurring problems for Tennessee, southern, and national nurseries. Two priority entomological issues identified by the nursery industry in the SNIPM-PSMP will be the focus of this project, including: 1) quarantine regulatory insects like IFA and JB that impose costly treatments on nursery stock and increase grower production costs and 2) trunk-attacking wood borers like flatheaded borers and ambrosia beetles, which kill trees or destroy plant marketability. Key research priorities identified by the SNIPM-PSMP will be addressed, including: 1) determination of factors that will reduce flatheaded appletree borer attacks, 2) development of improved systemic controls for borers, 3) development of more cost effective management for IFA and JB, 4) determination of granulate ambrosia beetle management before or after trees are attacked, and 5) general increased insecticide efficacy via better surfactants, improved rates, etc. Another grower priority area to be addressed was expansion of treatments that minimize impacts on other beneficial insects like pollinators and biological control agents.

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Improving Profitability and Reducing Pesticide Use in Nursery Crop Production
 Dr. Anthony Witcher
Nursery crop producers may encounter a wide range of factors (biotic and abiotic) that affect crop growth and quality including pests (insects, pathogens, weeds, etc.), mineral nutrition, and the environment (excessive rain, drought, wind, temperature extremes, etc.). Integrated pest management strategies are continually being developed to address the growing number of nursery crop pests. Likewise, best management practices for nursery crop production (methods for minimizing the environmental impact of producing plants) are being more widely implemented throughout the industry. Nevertheless, balancing the environmental and financial impacts of crop production is an ongoing challenge for nursery crop producers. The effectiveness and longevity of pesticides in alternative substrates used for nursery crop production will be evaluated to identify potential practices for reducing pesticide use. Alternative weed management techniques will be evaluated to determine suitability for use in nursery production systems. Methods will also be developed to prevent herbicide resistant weed establishment in nursery crops. Results from this research will be used to identify new nursery crop production practices that increase pest control but reduce use of synthetic pesticides.

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