NC1208: Biology, Etiology, and Management of Dollar Spot in Turfgrasses

(Multistate Research Project)

Status: Active

NC1208: Biology, Etiology, and Management of Dollar Spot in Turfgrasses

Duration: 10/01/2019 to 09/30/2024

Administrative Advisor(s):


NIFA Reps:


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). Many of the university representatives were extension faculty with direct linkages to the industry and strong first-hand experience with the challenges of this disease. Several also have diagnostic lab responsibilities and have seen many samples of this disease, including cases of fungicide resistance and other difficulties. The focus of the meeting was to discuss ongoing dollar spot research by each participating member and to identify key priorities for the development of more sustainable dollar spot management strategies. The priorities identified by this group at the meeting were (1) improving our understanding of the biology of the dollar spot pathogen, (2) developing dollar spot-resistant bentgrass cultivars and increasing their implementation by turfgrass managers, (3) implementing best cultural management techniques to decrease disease severity, (4) identifying targeted chemical control strategies that improve disease control and limit development of fungicide resistance, and (5) investigating potential cases of dollar spot antagonism and/or biological control. At the conclusion of this proposed project we will have a greater understanding of the pathogen’s biology that will foster improved cultural, chemical, and biological management strategies. It will also identify further knowledge gaps that need to be addressed in future dollar spot research. 


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 considered 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. Lastly, 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.


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). However, to our knowledge, this is the first attempt to coordinate dollar spot research efforts on a national scale. Coordination will reduce redundancy, provide additional testing sites for research, and foster new 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. More specific impacts will include, (1) development of an extension publication/fact sheet clarifying the new taxonomic structure of the dollar spot pathogen for the practitioner, (2) establishment of best management practices for dollar spot control in each region of the country, (3) identification and dissemination of resistant bentgrass cultivars from public and private turfgrass breeding programs, and (4) region-specific economic analysis of implementing the best management practices developed as a result of this research. Surveys of golf course superintendents will be conducted in each region in year 1 and again in year 5 to assess recommendation adoption and to document the 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 that the fungi associated with dollar spot are taxonomically distinct from other fungi and established a new fungal genus (Clarireedia) and split S. homoeocarpa into four distinct species. 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.


            Relatively little is known about the infection process of Clarireedia spp. or the epidemiology of these pathogens. Past research has suggested that Clarireedia (reported as S. homoeocarpa) overwinters as dormant mycelium in the thatch and soil and enters the turfgrass leaf blade through the stomata. 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). 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). A team of researchers from the University of Wisconsin – Madison, Rutgers University, and University of Massachusetts – Amherst have recently initiated a study to develop a molecular quantification assay for the dollar spot pathogen that can be used to quantify pre-symptomatic pathogen levels in the thatch. 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 have shown that increased nitrogen fertility has been found to decrease 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). Recent 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 for most golf course superintendents to apply (Townsend 2018). 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). Virginia Tech University recently found that regular applications of iron sulfate can be an effective dollar spot suppression technique, though the iron sulfate is phytotoxic to the turf when applied at rates high enough to provide complete dollar spot control (McCall et al. 2017). Researchers at the University of Wisconsin – Madison are currently investigating whether mixing lower rates of iron sulfate with lower rates of urea can provide dollar spot suppression comparable to a fungicide program without damaging the turf or exhibiting other non-desirable effects (i.e., high growth, increased brown patch and Pythium blight severity, or increased potential for surface and groundwater contamination) of high iron sulfate and high nitrogen programs. Lastly, Michigan State University recently observed that timing of irrigation scheduling impacted dollar spot severity (Dykema, 2014). 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 (http://www.ntep.org/) ratings. Unfortunately, Penncross is still used on many golf courses today and, when more current cultivars are selected they are often not the most resistant to this disease. For example, Pure Distinction is one of the more common cultivars chosen when reseeding golf courses and, although it 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 it’s 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 just 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 in the coming years. Thiophanate-methyl is no longer 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. 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 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 when disease pressure increases. In addition, researchers at the University of Maryland, Rutgers University, and the University of Wisconsin – Madison are currently researching the turfgrass microbiome and the potential for an ‘antagonistic microbiome’ that would provide natural suppression of dollar spot.

Objectives

  1. Improve our understanding of dollar spot biology and epidemiology through taxonomic analysis, molecular assay development, and host-pathogen interaction research.
  2. Assess current dollar spot resistance among bentgrass cultivars and new selections, identify barriers to their utilization in golf course establishment and renovations, and develop strategies for overcoming the identified barriers.
  3. Develop cultural-based dollar spot management strategies that combine multiple cultural practices (e.g., fertility, rolling, topdressing, irrigation) to limit dollar spot development in multiple geographic regions.
  4. Develop integrated and targeted chemical dollar spot management strategies that maintain current levels of disease control, potentially reduce chemical inputs, and limit development of fungicide resistant populations.
  5. Assess the ability of antagonistic organisms to suppress dollar spot when combined with the aforementioned cultural and chemical strategies.

Methods

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

 

            Taxonomic analysis will continue to be conducted by researchers from the USDA, Rutgers, UMass, and NC State 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 four 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 optimal growth conditions or 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 multiple universities will collect dollar spot isolates during the spring, summer and again during the fall for taxonomic/molecular analysis at USDA and Rutgers. In vitro temperature and fungicide sensitivity analysis will also be conducted, which will guide development of temporal-based field studies at multiple universities from distinct geographic regions.

            Epidemiology research will continue by researchers at Wisconsin, Rutgers, and UMass to develop a molecular assay to quantify the dollar spot fungus in the plant (leaves and thatch) pre-symptomatically. This assay should be completed in 2019 and can be used to conduct epidemiological assays related to pathogen dispersal, overwintering, and response to cultural and chemical controls. Select field studies using this molecular assay will begin in 2020.

 

Objective 2: Assess current dollar spot resistance among bentgrass cultivars and new selections, identify barriers to utilization in golf course establishment and renovations, and develop strategies for overcoming the identified barriers.

 

            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, some of the most commonly used creeping bentgrass cultivars remain highly susceptible to dollar spot. Researchers from Rutgers, other turfgrass breeding programs, and NTEP will provide an updated list of the most dollar spot resistant bentgrasses and identify genetic, environmental, and economic barriers to their inclusion in new bentgrass establishments. A survey of golf course superintendents from each region of the country will be conducted to identify industry barriers in addition to those identified by the breeders. Goals will be established to overcome these barriers so that improved dollar spot resistance will continue to be a priority in new bentgrass establishment. Rutgers University has initiated trials to determine the economic and environmental impact of transitioning 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. The results will be used to provide a more accurate representation of the potential costs and benefits for golf courses considering transitioning to resistant bentgrass cultivars as a means of encouraging the use of bentgrasses with improved resistance to this disease.

 

Objective 3: Develop cultural-based dollar spot management strategies that combine multiple practices (e.g., fertility, rolling, topdressing, irrigation) to limit dollar spot development in various regions.

 

            Nearly every participating university in this project has performed research related to cultural suppression of dollar spot. In Year 1 of the project the cultural practices that show the most promise regarding dollar spot suppression based on the available data will be identified by participating universities. Field studies will then be established at universities and cooperating golf courses in each geographic region of the country to determine how each practice reduces dollar spot individually and in combination with the other cultural practices relative to a fungicide program. The field studies will be conducted over multiple years in each location and an economic analysis will be conducted to determine cost comparisons of the best cultural practices identified in this project relative to traditional fungicide programs. Upon completion a list of best management practices will be developed to educate golf course superintendents on the impact that each cultural practice and the accumulation of multiple practices has on dollar spot severity.

 

Objective 4: Develop integrated and targeted chemical dollar spot management strategies that maintain current levels of disease control, potentially reduce chemical inputs, and limit development of fungicide resistant populations.

 

            Researchers at Rutgers, Connecticut, Wisconsin, Ohio State, Michigan State, Kansas State and others will continue to evaluate current and new fungicides and application strategies (rates, intervals, rotational programs, nozzles, water carrier, etc) for dollar spot control. These results will be shared at university field days, in technical research reports, trade publications, and the peer-reviewed publication Plant Disease Management Reports. Results will be used to update the dollar spot fungicide efficacy rankings published by the University of Kentucky and Rutgers University in the annual ‘Chemical Control of Turfgrass Diseases’ (http://www2.ca.uky.edu/agcomm/pubs/ppa/ppa1/ppa1.PDF) and the University of Wisconsin’s ‘Turf Management Mobile’ website (https://turfpests.wisc.edu/), as well as fungicide recommendations of other institutions involved in this project.

            Researchers at UMass will continue researching molecular aspects of dollar spot resistance development. In particular, they are developing molecular assays to quickly and accurately assess for particular mutations that confer resistance to multiple chemical classes (SDHI, benzimidazole, DMI). These assays will be used to assess dollar spot resistance in isolates collected from MA, NJ, WI, PA,, KS, CT and others. In addition, a number of isolates from the NC State dollar spot culture collection representing a range of fungicide use histories, turfgrass species, and geographic areas from throughout the world will be tested using this assay to identify patterns in resistance development.

            Researchers at Wisconsin have conducted initial analysis into the feasibility of using the Smith-Kerns Dollar Spot Prediction model to target dollar spot fungicide applications only to the areas of the course experiencing high disease pressure (as opposed to the current practice of spraying all greens or fairways at once). They are working with the USGA and private partners to develop small, portable environmental sensors that can calculate dollar spot pressure within the various microclimates on a golf course. The sensors will initially be tested on University Ridge Golf Course in Madison, WI and if promising results are observed then more sensors will be developed for additional testing by co-PIs on this project at golf courses representing different geographic areas of the country.

 

Objective 5: Assess the ability of antagonistic organisms 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. New and experimental biological compounds from various manufacturers will continue to be assessed at various universities across the country. The project team will compile the results from these studies and identify 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.

Measurement of Progress and Results

Outputs

  • Development of 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.
  • Develop 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.
  • Produce a taxonomic fact sheet to distribute to the golf course industry on the changes made to the taxonomic structure of the dollar spot pathogen. This will likely be a highly confusing change for most practitioners, and providing a standard set of information and describing why the change was made can help reduce the confusion in implementation of products and the reading of pesticide labels.
  • 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.
  • 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.
  • Conduct surveys of various aspects of the golf course management industry (superintendent, suppliers, breeders, etc) and publish results in both year 1 and year 5 of the project. Surveys in year 5 will focus on documenting the potential impact of recommendations from study results in years 2 and 3 of the project.
  • Develop a molecular assay that can accurately quantify dollar spot inoculum in the thatch/plant prior to symptom development. The assay from this USGA-funded study will then be used to conduct numerous epidemiological studies related to dollar spot.
  • Provide ‘proof of concept’ that precision dollar spot management on golf courses can be a profitable venture for one or more companies in private industry to develop dollar spot predicting weather stations that can be stationed around the golf course and help direct control strategies.

Outcomes or Projected Impacts

  • Improved exchange of information and coordination of research projects between various turf pathologists, agronomists, breeders, seed producers, and chemical manufacturers from around the country.
  • 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.
  • 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.
  • 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

(2019):Identify participating locations in cultural practice field studies, fungicide efficacy trials, and biological product evaluation trials and finalize experimental design of collaborative and interdependent trials. Initiate spring of 2020.

(2019):Choose host for dollar spot website and obtain domain name and establish basic structure.

(2019):WI, NJ, and MA complete development of molecular quantification assay and MA continue development of a molecular fungicide resistance assay.

(2019):Bring NC State dollar spot collection out of long-term storage and develop plan for adding additional isolates from various regions, seasons, and grass species/cultivars. Develop experimental design for in vitro testing of which Clarireedia spp. they belong to, optimal growth conditions, fungicide sensitivity, etc of the isolate collection.

(2019):Develop, implement, and analyze results of initial survey of turfgrass industry on current dollar spot management strategies

(2019):WI will conduct preliminary ‘precision dollar spot management’ field study

(2021):Continue cultural practice and fungicide efficacy field trials developed in 2020. Present trials at university field days.

(2021):Conduct in vitro assays on culture collection.

(2021):Add new and unique (different locations, times of year, cultivars, etc) dollar spot isolates to the culture collection.

(2021):WI will continue to conduct preliminary ‘precision dollar spot management’ field study.

(2021):Use molecular assays developed in 2020 (e.g., assays to quantify pathogen populations in the thatch and plant) to initiate new field studies exploring dollar spot biology and epidemiology.

(2021):Prepare and release fact sheet explaining taxonomic changes to the dollar spot pathogen.

(2021):Identify creeping bentgrass cultivars with highest dollar spot resistance and discuss strategies for increased adoption by golf course superintendents.

(2021):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.

(2022):Continue field and in vitro trials established in 2020 and present data where appropriate at university field days and conferences/seminars/trade shows.

(2022):Continue adding new and unique dollar spot isolates to the culture collection as needed.

(2022):Continue epidemiological and resistance management studies using molecular assays developed in 2020.

(2022):Release strategies to increase adoption of dollar spot resistant bentgrass cultivars in golf course construction and renovation. Strategies may be incorporated into a stand-alone fact sheet, included with another fact sheet, or published solely on the website.

(2022):WI will conclude preliminary ‘precision dollar spot management’ field study and present results and develop a recommendation for the feasibility of this technology moving forward.

(2022):Update dollar spot website as needed.

(2022):Determine the basic format of the future region-specific BMP publications.

(2023):Conclude and analyze data from 3 years of field and in vitro tests. Determine authorship roles for preparation of peer-reviewed manuscripts and begin manuscript preparation.

(2023):Continue epidemiological and resistance management studies using molecular assays developed in 2020.

(2023):Continue adding new and unique dollar spot isolates to the culture collection as needed.

(2023):Update dollar spot website as needed.

(2023):Continue preparation of region-specific BMP publications.

(2024):Conduct follow-up survey in spring of 2024, compare to 2020 survey, and publish the results publicly to document potential impact of the recommendations from this project.

(2024):Conclude epidemiological and resistance management studies using molecular assays. Determine authorship roles for preparation of peer-reviewed manuscripts and begin manuscript preparation.

(2024):Conclude manuscript preparation for field and in vitro research trials and submit for publication.

(2024):Identify knowledge gaps resulting from the research conducted in this project and discuss potential future funding of research to address the knowledge gap.

Projected Participation

View Appendix E: Participation

Outreach Plan

The annual meeting of NCRA232 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. Video conferencing will also be used on a regular (bimonthly) basis to check on progress of project participants and to enhance collaboration throughout the project. Information on this meeting and shared projects will be available on the NCRA232 Website and appropriate updates and information will be published on the Dollar Spot Management website as appropriate. 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 NCRA232 members will be updated annually and posted on the NCRA232 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.

Literature Cited

Beard, J., & Green, R. (1994). The role of turfgrasses in environmental protection and their benefits to humans. Journal of Environmental Quality, 23(3), 452-460.


Beaulieu, R., Medina, A., & Boehm, M. (2008). Oxalic acid production by Sclerotinia homoeocarpa: The causal agent of dollar spot. Phytopathology, 98(6), S20.


Bennett, F.T. (1937). Dollar spot disease on turf and its causal organism Sclerotinia homoeocarpa N.SP. Annals of Applied Biology, 24(2), 236-257.


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Land Grant Participating States/Institutions

KS, MI, NJ, OK, WI

Non Land Grant Participating States/Institutions

DFL Pickseed, United States Golf Association (USGA)
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