Duration: 10/01/2024 to 09/30/2029

Administrative Advisor(s):

NIFA Reps:

Non-Technical Summary

Dollar spot is the most economically important disease of managed turfgrass worldwide. The goal of this project is to develop an integrated set of cultural, chemical, and molecular strategies that maintains commercially acceptable control of dollar spot while reducing the reliance on synthetic fungicides. This goal will be achieved through the pursuit of five objectives:

1. Improve our understanding of dollar spot biology and epidemiology through phylogenetic analysis, molecular quantification, and host-pathogen interaction research.


2. Assess dollar spot resistance among new bentgrass cultivars and develop recommendations for their increased adoption.


3. Develop novel integrated dollar spot management strategies that includes under-studied cultural practices, use of fungicide alternative products, and the precision use of fungicides. Strategies will maintain or improve current levels of disease control, reduce reliance on chemical inputs, and limit development of fungicide resistant populations.


4. Assess the ability of antagonistic organisms and/or microbial communities to suppress dollar spot when combined with the aforementioned cultural and chemical strategies.


5. Improve communication strategies to disseminate research findings to the golf course management industry in a clear, rapid, and practical manner.

The target audience is turfgrass managers, specifically golf course superintendents, and they will benefit from this work through reduced use of pesticides and the financial, human health, and environmental health benefits that come along with that. The large and diverse project team will collaborate on a number of projects using a broad array of molecular and applied research tools to provide meaningful progress to suppress this difficult disease.

Statement of Issues and Justification

Turfgrass landscapes cover approximately 50 million acres of land in the United States and provide numerous environmental, recreational, and economic benefits (Beard and Green, 1994; National Turfgrass Federation, 2009).  The 14,000+ golf courses present in the U.S. only account for approximately 5% of the total turfgrass area; however, the golf industry is estimated to contribute over $84 billion to the U.S. economy (We Are Golf, 2018).  The intensive practices required to maintain putting greens, fairways, and tee boxes on a golf course can make the turfgrass in these areas susceptible to a number of disease, insect, and weed pests that can have a significant economic impact on golf course management.  

Dollar spot is caused by a group of fungal species from the newly formed genus Clarireedia (Salgado-Salazar et al. 2018). These fungi infect the leaves of turfgrass plants and causes severe blighting of the foliage in roughly circular infection centers 2 to 5 cm in diameter. Optimal environmental conditions for dollar spot development include temperatures between 15 and 30°C, humidity in excess of 85%, and prolonged periods of leaf wetness (Smiley et al. 2005). When optimal infection conditions persist, numerous dollar spot infection centers can appear and blight a large area of turf in just a few days.  Infection can progress into the plant crown and cause plant death, which leaves sunken depressions in the turf stand detracting from the playability and/or aesthetic value of the affected turf. Nearly all grass species that are grown for turf are susceptible to Clarireedia infection, and those commonly found on golf courses such as creeping bentgrass (Agrostis stolonifera) and annual bluegrass (Poa annua) are particularly susceptible (Smiley et al. 2005).  In addition, the optimal conditions for dollar spot symptom development (temperatures between 15 and 30°C and high humidity/prolonged leaf wetness) are common in many temperate areas of the U.S. from May until October.

The prolonged period of optimal conditions for dollar spot development in many temperate climates typically require 10 or more fungicide applications in a single season to obtain complete control of this disease.  Despite the resources employed to control dollar spot, relatively little is known about the basic biology and epidemiology of the Clarireedia spp. that cause this disease.  As a result, integrated dollar spot management plans have been largely ineffective and superintendents rely almost exclusively on chemical approaches for acceptable disease control.  However, numerous biological, economic, and environmental concerns have arisen in recent years following decades of reliance on fungicides.  From a biological standpoint, Clarireedia develops resistance to fungicides very quickly, and over-reliance on chemical control has led to reported resistance to the benzimidazole, demethylation inhibitor, dicarboxymide, and succinate dehydrogenase inhibitor fungicide classes (Golembiewski et al. 1995; Sang et al. 2015). From an economic standpoint, many golf facilities across the country struggle to afford the season-long fungicide programs required to control this disease. Finally, societal and regulatory pressures have led to an increasing desire to use fewer chemical inputs in golf course management and fewer newer turfgrass fungicides coming to the market (Pimental et al. 1992; Tomer et al. 2015).  These significant concerns indicate that there is an urgent need for multi-disciplinary/institutional collaborative research that will produce new and more sustainable dollar spot control strategies.  

Need as indicated by stakeholders. In February 2018, a broad group of representatives met in San Antonio, TX as part of North Central Development Committee Project 232.  The group included university and government researchers representing turfgrass pathology, breeding, physiology and management, as well as industry stakeholders including a representative from the United States Golf Association (USGA). This group indicated that dollar spot was one of the most important and costly diseases for turfgrass managers to manage on golf courses around the world. This need as indicated by the stakeholders led to the creation of NC1208, which has been in place since 2019. The NC1208 group has been effective at addressing many of the stated objectives in that project, particularly given the disruption of the COVID-19 pandemic, and currently has 1 project completed and in manuscript preparation, another project complete and in preparation for an extension publication/fact sheet, and 3 other ongoing projects. Despite our productivity, dollar spot severity continues to increase around the world as a result of climate change, particularly in Europe and Scandinavia where chemical control is severely limited. If funded for another 5 years NC1208 will continue ongoing research projects related to increasing adoption of best management practices, use of resistant bentgrass cultivars, and implementation of disease predictive modeling. The team has also discussed new projects related to improving the efficacy of biocontrol, harnessing the turfgrass microbiome to suppress the dollar spot pathogen, and novel cultural practices and fungicide alternatives for dollar spot suppression. Over the next 5 years we will have a greater understanding of the pathogen’s biology that will foster improved cultural, chemical, and biological management strategies to meet the increasing threat that dollar spot poses to amenity turf around the world.

The importance of the work and what the consequences are if it is not done. Dollar spot is the most commonly observed disease of turfgrasses on golf courses throughout the world.  Approximately 70% of U.S. golf course superintendents in the Midwest and Northeast consider dollar spot to be their primary disease, and the average golf course superintendent in these regions spent approximately $15,000 and $28,000, respectively, to control dollar spot in 2016 (Hirvela, personal communication).  In the U.S., more fungicide is used and more money is spent to control dollar than any other turfgrass disease on golf courses (Hirvela, personal communication).  If the above work is not conducted, it is likely that golf course superintendents will remain heavily reliant on chemical control of dollar spot and that new cases of fungicide resistance will continue to be reported.  This will be financially disadvantageous to the golf course facility and may result in more rapid development of multi-class fungicide resistant populations of Clarireedia and increasing concerns surrounding the non-target impacts of fungicide usage on human and environmental health.

The technical feasibility of the research: The scientific team assembled for this project includes approximately two-dozen university and government researchers representing all geographic areas of the United States except for the arid southwest where dollar spot is rarely observed.  The team has expertise in all areas related to the stated priority areas: applied and molecular aspects of turfgrass pathology, breeding, management, physiology, and genetics.  Nearly every project member has experience researching dollar spot in some capacity and over half of the members have over 10 years of experience working with this disease and have published numerous peer-reviewed research articles on the subject.  In addition, nearly all members reside at land grant institutions and have the field and/or laboratory resources at their respective institutions needed to actively contribute to their area of the project.  Many project members have appointments in Cooperative Extension and can use their appointment to successfully communicate and disseminate project results out to the broader turfgrass community. Lastly, the team has been highly productive in conducting coordinated research over the first 5 years of NC1208 and has numerous additional research projects in development if the project is to receive an additional 5 years of funding.

The advantages for doing the work as a multistate effort: Dollar spot is one of the few turfgrass diseases that commonly occurs on multiple turfgrass species, including both warm-season and cool-season turfgrasses. However, many attributes of the pathogen and methods for managing the disease differ between geographic regions.  For instance, research published in early 2018 indicated that different species of Clarireedia are present on warm vs cool-season turfs but produce similar disease symptomology (Salgado-Salazar et al. 2018).  In addition, regional environmental conditions result in higher pressure, and more fungicide required, in certain regions relative to others. The higher fungicide usage on certain turf species and in certain regions has led to more rapid development of resistant populations of Clarireedia relative to other regions and species, with important regional ramifications for control.  Dollar spot is a common turfgrass disease with a broad geographic range and numerous unique regional characteristics, making it an ideal candidate for multi-state collaboration.

 

What the likely impacts will be from successfully completing the work: Dozens of individual researchers have conducted dollar spot research since the pathogen was first characterized in the United Kingdom in 1937 (Bennett 1937).  While significant progress has been made during the first 5 years of the NC1208 project, our collaborative research needs to continue to provide the greatest benefits to the turfgrass industry. Coordination will reduce redundancy, provide additional testing sites for research, and foster the continuation of collaborative research projects that can be used to obtain additional research funding and speed the development of effective best management practices for the control of this disease with fewer chemical inputs. Specific impacts if we are to receive support for the next five years include, (1) establishment of best management practices for dollar spot control in each region of the country, (2) development of an extension publication/fact sheet describing how best to implement dollar spot-resistant cultivars into existing stands AND how best to manage them using fewer chemical inputs, and (3) creation of a central dollar spot website that can serve as a single, science-based resource for dollar spot management for practitioners all around the world. Surveys of golf course superintendents will be conducted in year 1 and again in year 5 of the new project to assess potential adaptation of recommendations and to document potential economic impact of the team’s recommendations.

Related, Current and Previous Work

Dollar spot taxonomy, biology, and epidemiology.  Dollar spot was first described as Sclerotinia homoeocarpa in 1937 by F.T. Bennett in the U.K. (Bennett 1937). He isolated the pathogen into pure culture, proved its pathogenicity, and observed the sexual stage of the fungus. Based on his observation of sclerotial structures in pure culture and other morphological characteristics, Bennett placed this pathogen in the Family Sclerotiniaceae and the Genus Sclerotinia. It was evident for many years that the dollar spot pathogen had been misclassified as a Sclerotinia. However, the true identity of the causal agent remained unresolved until Salgado-Salazar et al. (2018) recently determined the dollar spot pathogen as four distinct species that are taxonomically distinct from other fungi and established a new fungal genus (Clarireedia). C. jacksonii is the primary species present on cool-season turfgrasses, C. monteithiana is the primary species found on warm-season turfgrasses, and C. homoeocarpa and C. bennettii appear to primarily occur on Festuca grasses from the United Kingdom. Recently, two new species of Clarireedia, C. paspali and C. hainanense, were discovered in China and have proven pathogenic to commercial turfgrass species in the U.S (Hu et al. 2019; Zhang et al. 2022; Bahri et al. 2023). The distribution of these species outside of China is unclear. The continued discovery of new Clarireedia species indicates our understanding of this pathogenic genus is still in its infancy.

            Relatively little is known about the infection process of Clarireedia spp. or the epidemiology of these pathogens. Past research suggests Clarireedia (reported as S. homoeocarpa) overwinters as dormant mycelium in the thatch and soil and enters the turfgrass leaf blade through the stomata. Past research has investigated it’s spatial aggregation and also demonstrated that the fungus can infect bentgrass seed and potential enter golf course environments during seeding events (Horvath et al. 2007; Rioux et al. 2014). Oxalic acid has been implicated as a virulence factor in the infection process, though the importance of this relationship in the newly identified species remains unclear (Beaulieu et al. 2008; Rioux 2014). Oxalic acid was further confirmed as one of the virulent factors by genomic and transcriptomic analyses along with other pathways including glycosyl hydrolase enzymes and serine proteases production (Orshinsky et al. 2012; Bahri et al. 2023). A dollar spot prediction model was developed for S. homoeocarpa by researchers from the University of Wisconsin – Madison and NC State University and the model is currently used by golf course superintendents around the world to more appropriately time fungicide applications based on environmental conditions (Smith and Kerns et al. 2018). Molecular quantification assay targeting the ITS rDNA region of Clarireedia was developed to detect and quantify pre-symptomatic pathogen levels from turfgrass foliar samples (Groben et al. 2020). However, improvements are needed to enhance the practical use of the assay, the data translatability, and assay specificity and consistency. Once completed, this assay will be used to learn more about the epidemiology of Clarireedia and the impacts that various cultural and chemical practices can have on the pathogen population.

Cultural control strategies:  Numerous cultural strategies have been researched for their efficacy against dollar spot; however, they have not been validated for the various species of Clarireedia.  Previous research on S. homoeocarpa shows that increased nitrogen fertility decreases dollar spot severity, though to date no studies have provided acceptable dollar spot control using solely fertility-based practices (Williams et al 1996; Golembiewski et al. 1998). Research from the University of Wisconsin – Madison showed that nitrogen rates of 29 kg ha^-1 applied as a foliar urea spray every two weeks provided dollar spot suppression comparable to a fungicide program, however this is an impractical level of nitrogen to apply for maintenance of golf putting greens (Townsend et al. 2021).  Research at Michigan State University indicated that regular rolling on golf course putting greens using a lightweight mechanical roller provided a significant reduction in dollar spot severity, though again typically not to acceptable levels without assistance from fungicides (Giordano et al. 2012).  One of the primary projects of the first NC1208 research project was to evaluate the impacts of combining fertility, dew removal, and plant growth regulator cultural practices on dollar spot suppression in Wisconsin, Virginia, Pennsylvania, Ohio, and Kansas. The results found that fertility and dew removal reduced dollar spot by approximately 30% compared to the non-treated plots, but no combination of cultural practices resulted in commercially acceptable results. This manuscript is in the final stages of preparation for submission to a peer-reviewed journal.

Additional research by NC1208 project members has investigated the use of iron sulfate and irrigation timing on dollar spot suppression. McCall et al (2017) found regular applications of iron sulfate can be an effective suppressing dollar spot, though the iron sulfate is phytotoxic to the turf when applied at rates high enough to provide complete dollar spot control. Dykema (2014) observed that timing of irrigation scheduling impacted dollar spot severity. Traditional turf pathology recommendations have been to irrigate in the early morning hours to limit leaf wetness duration, but the recent MSU work found that irrigation applied the previous evening significantly reduced dollar spot relative to early morning irrigation.

           

Host resistance: Dollar spot is commonly observed on numerous cool and warm-season turfgrass species.  It is most severe on creeping bentgrass and annual bluegrass, both of which are primary grasses found on golf course putting greens, fairways, and tees in temperate climates throughout the world.  The most common cultivar of creeping bentgrass over the past 60 years has been ‘Penncross’, developed by Dr. Musser at Penn State University and released in 1955.  This cultivar has many benefits and endures to this day on many golf courses; however, it is highly susceptible to dollar spot. 

Dollar spot resistance in creeping bentgrass has been shown to be under strong genetic control (Bonos et al., 2003; Bonos, 2006), but no cultivars exhibit immunity (Bonos, 2005). Recent research has identified several quantitative trait loci associated with dollar spot resistance (Honig et al., 2014) however, the underlying mechanism providing improved tolerance among bentgrass cultivars is still unknown. Despite this, recent breeding efforts at Rutgers University and elsewhere have developed new cultivars of creeping bentgrass with increased levels of dollar spot resistance, and some (Memorial, Declaration, Flagstick, Piranha, Chinook) have been reported to have high levels of dollar spot resistance in recent National Turfgrass Evaluation Program (NTEP; http://www.ntep.org/) trials. Unfortunately, Penncross is still used on many golf courses today, and even when current cultivars are selected for renovation, dollar spot resistance is not commonly considered. For example, ‘Pure Distinction’ is one of the more common cultivars chosen when reseeding golf courses and, although the cultivar has a very dense growth habit, it is also more susceptible to dollar spot relative to the other cultivars listed above.  Thus, the continued development of bentgrass cultivars that combine attributes of color, growth habit, and drought tolerance with resistance to dollar spot and other diseases and making superintendents aware of these improved cultivars will be an important aspect of the integrated dollar spot management strategies developed by this project.

 

Chemical control, fungicide resistance, and biological control: The areas of chemical control and fungicide resistance have received the most attention from turfgrass researchers relative to other areas of the dollar spot system. Chlorothalonil is a multi-site, contact fungicide that has been a staple of effective dollar spot control since its release on to the turf market in 1966. Thiophanate-methyl was the first penetrant fungicide for use in dollar spot control and was widely used for dollar spot management until resistance rapidly decreased its efficacy in the 1970’s (Warren et al. 1974). Demethylation inhibitor (DMI) fungicides have been key components of dollar spot management programs since their release in the 1980’s, and though widespread resistance to these and the dicarboxymide fungicides has been documented they remain important contributors to dollar spot management today (Golembiewski et al. 1995).  The most recent (2000’s) chemical class with strong efficacy against dollar spot is the succinate dehydrogenase inhibitor (SDHI) class of fungicides, though isolated reports of fungicide resistance have already been reported to certain SDHI fungicides (Sang et al. 2015).  Proper application strategies are as important as product selection, and research into optimum water carrier volume and nozzle selection has been conducted in recent years at Penn State University, University of Connecticut, Rutgers University, and Kansas State University.

            Fungicide resistance is a growing problem in dollar spot management, and with fewer new chemical classes coming to the turfgrass market it is a problem that will only increase.  Thiophanate-methyl is no longer effective or used for dollar spot control due to widespread and complete resistance (Detweiler et al. 1983; Burpee 1997). Resistance to DMI fungicides is well characterized and widespread, though the quantitative nature of DMI resistance allows most golf courses to still use DMI fungicides for dollar spot control with higher rates and shorter reapplication intervals (Golembiewski et al. 1995; Gilstrap 2005).  Resistance to SDHI fungicides is not yet widespread, though there is ample evidence that resistance to boscalid exists in numerous dollar spot populations throughout the U.S. and that resistance will likely develop in newer subgroups within the SDHI chemistry. In addition, chlorothalonil, a multisite inhibitor with no known resistance issues, is currently under EPA review and may be limited to application rates that would render its use ineffective.  Most of the above resistance work in turf was conducted using receptor-based assays, though recent and ongoing research at the University of Massachusetts – Amherst is investigating non-receptor based mechanisms for resistance that include fungicide metabolism through cytochrome P450 monooxygenases and fungicide efflux via ABC transporter molecules (Sang et al. 2015).

            Several biological products are currently registered for dollar spot control, including Rhapsody (Bacillus subtilis), Root and Turf Shield (Trichoderma harzianum), and EcoGuard (Bacillus licheniformus). Other products have been evaluated and commercially available in the past, including BioJect Spot-Less (Pseudomonas aureofaciens).  To date, these products can reduce dollar spot during times of low disease pressure, but typically fail to provide adequate control under moderate or high disease pressure. Researchers at Rutgers University and the University of Wisconsin – Madison sampled 8 golf courses from around the Northeast and Midwest and found evidence of dollar spot ‘suppressive’ soils and are currently researching the turfgrass microbiome to identify the organisms contributing to this antagonism.

Objectives

1. Improve our understanding of dollar spot biology and epidemiology through phylogenetic analysis, molecular quantification, and host-pathogen interaction research.
   
2. Assess dollar spot resistance among new bentgrass cultivars and develop recommendations for their increased adoption.
   
3. Develop novel integrated dollar spot management strategies that includes under-studied cultural practices, use of fungicide alternative products, and the precision use of fungicides. Strategies will maintain or improve current levels of disease control, reduce reliance on chemical inputs, and limit development of fungicide resistant populations.
   
4. Assess the ability of antagonistic organisms and/or microbial communities to suppress dollar spot when combined with the aforementioned cultural and chemical strategies.
   
5. Improve communication strategies to disseminate research findings to the golf course management industry in a clear, rapid, and practical manner.
   

Methods

Objective 1: Improve our understanding of dollar spot biology and epidemiology through phylogenetic analysis, molecular quantification, and host-pathogen interaction research.

 

            Strain and species identification, characterization, and taxonomic analysis will continue to be conducted by researchers from Rutgers, UMass, and the University of Wisconsin - Madison to assess the recent taxonomic assignments established by Salgado-Salazar et al. (2018). In particular, a large collection of dollar spot isolates exists at NC State University. That collection, as well as additional dollar spot isolates collected from around the world, will be characterized using the six new species classifications to determine the taxonomic variability that exists within dollar spot from around the world. Individual isolates from each species will then be assessed in vitro to determine if there are any differences in host range, pathogenicity, optimal growth conditions and response to fungicides. Differences observed in vitro will be used to develop region-specific field studies to determine species responses to cultural and chemical inputs as well as cultivar resistance.

            In addition, specific attention by turfgrass pathologists has been given in recent years to the temporal aspect of dollar spot development. In particular, dollar spot occurring during the fall months has seemed to increase in severity and differential responses to creeping bentgrass resistance screening has been observed in the spring vs the summer vs the fall (e.g., fall isolates appear to cause extensive damage [deep pitting of the turf surface] compared to spring and summer isolates). Researchers from Wisconsin, Purdue, and Rutgers conducted a small temporal analysis of the genetic differences in dollar spot between summer and fall as part of the original NC1208 project and found limited genetic variability between the two time points. However, this sampling was limited and additional sampling and sequencing work is warranted.

            Epidemiology research will continue by researchers at Wisconsin, Rutgers, and UMass to improve upon a molecular assay to quantify the dollar spot fungus in the plant (leaves and thatch) pre-symptomatically. Select field studies using this molecular assay were initiated in 2020 and the improvement on the genetic marker and sampling methods are being optimized. Specifically, protein-encoding DNA and pathogenicity-associated RNA markers are being developed by USDA, University of Wisconsin – Madison and Rutgers University to avoid the noise introduced by the variable copy number of ITS region across Clarireedia spp. and detect the near real-time activity of dollar spot. Also, the application of ddPCR and dPCR will be evaluated to enhance pathogen detection and quantification. Practical sampling methods are being developed by Rutgers University so that the turfgrass managers can leverage the developed molecular tools by submitting samples to service labs and plan their disease control program accordingly.

            Research by project members at Tennessee have begun transcriptomic analysis of the dollar spot-bentgrass pathosystem using RNA-seq. This approach will provide important clues to the infection process of Clarireedia spp. and likely provide directions for future collaborative research among NC1208 project members that may produce novel control strategies.

 

Objective 2: Assess dollar spot resistance among new bentgrass cultivars and develop recommendations for their increased adoption.

 

            Multiple creeping bentgrass cultivars have been developed at Rutgers University, Michigan State, and elsewhere in recent years with improved resistance to dollar spot.  Many of these cultivars have been tested in the field and incorporated into new golf course construction and golf course renovations around the world.  However, despite the obvious benefit, few facilities have renovated to a new bentgrass cultivar in the last decade and only 38% of those that did have changed their disease management practices. Concerns over lost revenue due to course closure, potential encouragement of annual bluegrass invasion and unknown agronomic qualities of new cultivars are presumable causes for hesitancy. A multi-institutional approach utilizing research and demonstration trials will be conducted to address these concerns.

Researchers at Rutgers and other bentgrass breeding programs working in coordination with NTEP will provide an updated list of the most dollar spot resistant bentgrasses and other species important in the lawn and landscape. Rutgers University has initiated trials to determine the economic and environmental impact of traditional renovation to a more resistant bentgrass cultivar through reduced pesticide usage, and these trials will be continued and replicated at other universities to determine region-specific impacts. In addition, recently initiated research led by Purdue and replicated at Penn State and Wisconsin aims to evaluate methods of interseeding dollar spot cultivars into an existing susceptible stand at fairway height, which could reduce or eliminate the need for course closure and limit fungicide usage on a larger acreage (30-40 A/golf course). Conversion success will be assessed through dollar spot severity and fungicide reduction in the field and with cultivar identification of clipping samples with molecular markers developed in cooperation with USDA-ARS researchers. The results of these multistate cooperative efforts will be translated into a more accurate representation of the true costs and benefits of transitioning to dollar spot resistant bentgrass cultivars, with the target of encouraging more widespread use.

 

Objective 3: Develop novel integrated dollar spot management strategies that includes under-studied cultural practices, use of fungicide alternative products, and the precision use of fungicides. Strategies will maintain or improve current levels of disease control, reduce reliance on chemical inputs, and limit development of fungicide resistant populations.

 

            The impact of cultural practices on dollar spot severity has been the subject of research by nearly every participating university in this project. Progress in our understanding of the impact of fertility, lightweight rolling, topdressing and other management practices have formed a basis for a comprehensive management strategy that still needs further investigation and refinement. Further evaluation of topdressing with composts and alternate amendments, the effect of temperature and the warming climate on dollar spot incidence and fungicide efficacy, and other related aspects will add necessary layers to management programs in both the golf and lawn and landscape sectors to further reduce reliance on fungicides for control. Additional research on fungicide application strategies, including precision fungicide application with drone/image recognition in conjunction with GPS mapping, will also aid in maximizing fungicide efficacy and reducing application frequency.

            Alternatives to traditional fungicides are also being actively investigated by NC1208 project members. Project members from Wisconsin and Virginia Tech have collaborated on the use of iron sulfate for suppression of dollar spot in the recent past and are completing a manuscript for peer review. They will continue to investigate optimal usage of iron sulfate and how it can be incorporated into integrated dollar spot management programs. Additionally, Wisconsin researchers have been investigating the efficacy of plant-based fungicides such as poacic acid for dollar spot control and in the next 5-year project will work collaboratively with other project members to test this product in other locations. Researchers at Maryland have been investigating the use of UVC light for dollar spot suppression and has observed favorable responses in vitro and intends to work with other NC1208 project members on field applications of this research in the next 5 years. Researchers at both Wisconsin and Maryland have been researching RNAi approaches to dollar spot control. Target genes have been identified and successful in vitro tests have been completed and the potential for field applications of this technology will be another component that the NC1208 project members will attempt to accomplish in the next 5 years.

In general, multiple-year field studies will be established at universities and cooperating golf courses in each geographic region to assess the impact of multiple cultural practices and fungicide alternatives. Effective strategies will be compiled into a comprehensive list that details the cost and expected reduction of disease from single and multiple disease management practices.

 

Objective 4: Assess the ability of antagonistic organisms and/or microbial communities to suppress dollar spot when combined with the aforementioned cultural and chemical strategies.

 

            Researchers at Rutgers, Maryland, Michigan State, Wisconsin, and others have assessed biological products for their efficacy against dollar spot and to date have not identified any commercially acceptable products for the turfgrass market. New and experimental biological compounds from various manufacturers will continue to be assessed at various universities across the country during the next 5 year project and the project team will compile the results from these studies to identify any promising biological products for dollar spot control. Products identified as promising will be tested on their own, in conjunction with various cultural practices, improved bentgrass cultivars, and with lower use rate fungicide programs to determine whether biological products can be an effective dollar spot management strategy.  An economic analysis will be conducted to provide golf course superintendents approximate costs of implementing biological products into their program.

Researchers at Clemson University, the University of Maryland, and the University of Connecticut that are part of this project team have begun to investigate the niche clearing strategy to enhance the establishment of exogenously applied dollar spot antagonistic organisms. This collaborative work will continue in the next project with the goal of developing strategies to enhance the effectiveness of biocontrol products on turfgrass. In addition, NC1208 project members at the University of Wisconsin-Madison and Rutgers identified potential dollar spot suppressive microbial communities in a preliminary study that sampled 8 different golf courses from around the Midwest and Northeast. The researchers used advanced high throughput sequencing techniques to identify potential antagonistic microbes and will collaborate on future research in the next 5 years to further identify dollar spot suppressive microbes and strategies for their enhancement.

 

Objective 5: Improve communication strategies to disseminate research findings to the golf course management industry in a clear, rapid, and practical manner.

            Communication of the research findings from this project is essential to adoption by turfgrass managers. The project team consists of numerous extension specialists at land-grant universities from the Midwest (Wisconsin, Indiana, Michigan, Ohio), the Northeast (New Jersey, Massachusetts, Connecticut), the mid-Atlantic (Maryland, Virginia), and the Southeast (South Carolina). Partners from the turfgrass industry including the United States Golf Association, NTEP, the USDA-ARS, and private industry affiliates also constitute this project team and will assist in communicating the research findings to their clientele. Research findings will be disseminated through traditional means such as field day demonstrations, presentations at trade association meetings, and in trade journal articles. Research findings will also be disseminated through more progressive means such as virtual field days and the use of social media. A central website will be created by the end of Year 3 to house the research findings from this project, as well as general information about dollar spot management, with the goal of it being the central node of all science-based information related to dollar spot for turfgrass managers and turfgrass researchers alike.

Measurement of Progress and Results

Outputs

• 1. Publish the results of NC1208 projects in peer-reviewed journals. One manuscript related to an NC1208 project is in the final stages of preparation and 2024 will likely be the final field season for another. Two additional NC1208 projects are ongoing and will produce peer-reviewed manuscripts before the end of the next 5-year project.
• 2. Develop an extension fact sheet detailing the results of the resistant cultivar survey and best management practices for managing dollar spot on resistant bentgrass cultivars. This survey was conducted during the first NC1208 project and focused on how superintendents choose cultivars during renovations and yielded a wealth of information that can be included to help drive increased selection of dollar spot-resistant cultivars AND reduce pesticide usage on those resistant cultivars.
• 3. Host a ‘Dollar Spot Conference’ that is organized by NC1208 but invite numerous groups from private industry that includes golf course superintendents, chemical company representatives, turfgrass breeders, and others. The focus of this conference will be to summarize current knowledge related to dollar spot management, identify knowledge gaps and future threats to current management practices, and develop strategies to address those gaps and threats.
• 4. Develop region-specific BMP publications for dollar spot management that factor in effective fungicide selection and timing, cultural practice implementation, use of fungicide alternative products, fungicide resistance management, and resistant cultivar selection. All publications will be written in a consistent format but tailored to the specific challenges faced by golf course superintendents managing dollar spot in various regions of the country.
• 5. Conduct a full or half day dollar spot management seminar at the Golf Industry Show (an annual, highly-attended national educational conference) focusing on the results obtained in this project and how they can be implemented by golf course superintendents.
• 6. Display field research plots at university field days across the country and discuss combined results from all locations at conferences and trade shows to educate the golf course superintendent on the results being obtained.
• 7. Create and maintain a ‘dollar spot management’ website intended for the golf course superintendent that provides information related to dollar spot biology and that will act as a repository for the results obtained in the various field, laboratory, and controlled environment chamber studies conducted as part of this project. The project team will use their own individual social media platforms to drive stakeholders to this site.
• 8. Conduct one or more ‘virtual field days’ to discuss the results of particular NC1208 projects with interested parties from a global audience. This may be of particularly interest to turfgrass managers in Europe and Scandinavia where dollar spot is rapidly increasing in severity due to climate change and where few fungicides are allowed for use.
• 9. Improve upon the molecular assay developed in the previous project to accurately quantify dollar spot inoculum in the thatch/plant prior to symptom development. Deploy this improved assay to improve our knowledge of the epidemiology and biology of the pathogen.
• 10. Further demonstrate the utility and cost savings of ‘precision’ dollar spot management and work with private industry to develop small, affordable weather stations that can be deployed across a golf course to predict dollar spot development.

Outcomes or Projected Impacts

• 1. Improved exchange of information and coordination of research projects between various turf pathologists, agronomists, breeders, seed producers, and chemical manufacturers from around the country.
• 2. Updated dollar spot control recommendations that take into account spatial and temporal effects on pathogen genetics, disease predictive modeling, host resistance, implementation of cultural practices and alternative products, new fungicide products and application strategies, and fungicide resistance management.
• 3. Adoption of the updated recommendations by golf course superintendents will result in an integrated approach to dollar spot management that will lower the non-target impact of dollar spot control, reduce inputs and costs to the golf course superintendent, and retain the highly effective dollar spot control currently demanded by the clientele.
• 4. Identification of knowledge gaps related to areas such as pathogen genetics, host-pathogen relationships, fungicide resistance, etc that will require additional research and funding to address.

Milestones

(2024):Summarize NC1208 projects underway and discuss new studies that will help us address the project objectives. Continuing studies likely to include ‘Interseeding of resistant bentgrass cultivars’ (IN, WI, PA) and ‘Dollar spot model thresholds for resistant cultivars (WI, MI, NJ).

(2024):Choose host for dollar spot website and obtain domain name and establish basic structure.

(2024):WI and NJ complete improved molecular quantification assay and develop additional epidemiological studies for future years.

(2024):Complete extension publication focused on selecting resistant cultivars and dollar spot management on resistant cultivars.

(2024):Publish ‘cultural practices’ study from original NC1208 project.

(2024):Select date and location to host dollar spot conference in 2025.

(2025):Hold Dollar Spot Management conference

(2025):Continue ongoing field studies and initiate new studies planned in 2024.

(2025):Use improved molecular assay developed in 2024 to initiate new field studies exploring dollar spot biology and epidemiology.

(2025):Begin preparation of region-specific BMP fact sheets. Includes which regions will have unique fact sheets, who will lead each region’s fact sheet, and overall format.

(2025):Release and publicize dollar spot website as a central location for dollar spot management information, making clear new results of national collaborative studies will be added as they become available. Use our existing social media platforms to drive stakeholders to this content.

(2026):Complete and publish studies initiated in the previous NC1208 project.

(2026):Hold NC1208 annual meeting.

(2026):Continue field trials established in 2024 and present data where appropriate at university field days and conferences/seminars/trade shows.

(2026):Continue epidemiological and resistance management studies using molecular assays developed in 2024.

(2027):Conclude and analyze data from 3 years of research. Determine authorship roles for preparation of peer-reviewed manuscripts and begin manuscript preparation.

(2027):Continue epidemiological and resistance management studies using molecular assays developed in 2024.

(2027):Update dollar spot website as needed.

(2027):Continue preparation of region-specific BMP publications.

(2027):Hold NC1208 annual meeting

(2028):Conduct survey in spring of 2028 to assess industry awareness of our NC1208 project and the research results. Results will be published publicly to document potential impact of the recommendations from this project.

(2028):Conclude manuscript preparation for all research trials and submit for publication.

(2028):Identify knowledge gaps resulting from the research conducted in this project and discuss potential future funding of research to address the knowledge gap.

(2028):Hold NC1208 annual meeting

Projected Participation

View Appendix E: Participation

Outreach Plan

The annual meeting of NC1208 will serve as the primary mechanism for project members and affiliated interested parties to stay updated on data collected to date, problems to address, and future activities related to the project.  Group emails will be the primary mode of contact for regular updates outside of the annual meeting, but video conferencing will also be used as needed to address more significant issues that arise. Information on this meeting and shared projects will be available on the NC1208 website and appropriate updates and information will be published on the Dollar Spot Management website once the website is up and running. Project members, many of whom have extension appointments, will also make research results available through refereed and non-refereed scientific journals, extension bulletins, national/international conferences, workshops, and social media. Upon completion of projects, results and recommendations will be disseminated to the turfgrass industry and the general public via publications in the popular press, social media, magazines, peer-reviewed journals, oral and written presentations at workshops, and at grower field days. A list of all publications developed by NC1208 members will be updated annually and posted on the NC1208 Website in NIMSS. The region-specific BMP publications and fact sheets related to other aspects of the project will provide a unified set of recommendations to offer to golf course superintendents based on their location and other aspects of their golf course environment.  These BMP publications and their recommendations will be disseminated in the same manner as described above.

Organization/Governance

The organization of project will be established in accordance with the format suggested in the “Manual for Cooperative Regional Research”. One person at each participating institution or agency will be designated, with approval of the institution’s or agency’s director, as the voting member of the Technical Committee. Other individuals and interested parties are encouraged to participate as non-voting committee members. Each year, members will elect a Secretary. The Secretary, whose duties begin the following year, becomes Chair-elect in year 2 and Chair in year 3.

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Attachments

Land Grant Participating States/Institutions

IN, MD, MI, VA, WI

Non Land Grant Participating States/Institutions