NCCC214: Biology, Etiology, and Management of Dollar Spot in Turfgrasses
Statement of Issues and Justification
Dollar spot, caused by the fungus Sclerotinia homoeocarpa, is the most common and important turfgrass disease worldwide. This pathogen infects all grass species that are grown for turf and develops across a broad range of climatic conditions. In the United States, 42% of turfgrass managers list dollar spot as their primary disease problem, and approximately 35% of fungicides applied to turf are for control of this disease.The dollar spot pathogen initially infects the leaves of turfgrass plants, causing severe blighting of the foliage in discrete infection centers up to 6 inches in diameter. Over time and under ideal environmental conditions, infection progresses into the plant's crown and causes death, leaving a sunken depression in the turf stand that detracts from the playability and/or aesthetic value of the affected turf. In many areas of the U.S., weather conditions can be favorable for dollar spot development throughout the entire growing season. During periods of intense disease activity, stands of susceptible turf can be severely damaged in a short period of time.
Despite the global significance of dollar spot, relatively little is known about the basic biology and ecology of S. homoeocarpa and its interactions with turfgrass hosts. Researchers are just starting to understand some of the most fundamental aspects of this pathosystem, such as the correct taxonomic placement for the pathogen and how the pathogen initiates infection within the turf host. If we are to develop and implement integrated pest management strategies, advances in our understanding of the basic biology, ecology and epidemiology of the dollar spot pathosystem are needed.
Due to our lack of knowledge about the dollar spot system, it is impossible to develop management plans that are truly integrated. Most turfgrass managers rely solely on chemical approaches to manage the disease, applying fungicides every 14 to 21 days when disease activity is observed. This approach is not sustainable from biological, economical, environmental standpoints. First, from a biological standpoint, S. homoeocarpa develops resistance to fungicides very quickly and over-reliance on chemical control has led to widespread resistance in pathogen populations. Second, from an economic standpoint, the turfgrass industry has been severely affected by the economic downturn and many facilities can no longer afford chemically-based strategies for dollar spot control. Finally, from an environmental standpoint the chemical options for control of dollar spot are dwindling rapidly due to environmental concerns and increasing federal/state/local regulations.
These challenges have led to renewed interest in research of the dollar spot pathosystem. The group of scientists currently working on dollar spot come from a diversity of backgrounds, including plant breeding, biological control, genomics, epidemiology, disease forecasting, economics, population biology, turfgrass management, molecular plant-microbe interactions, and fungicide resistance. The goal of this regional project is to provide a forum for exchange of ideas among this diverse group of scientists and encourage multi-disciplinary research that would not be possible within a single institution. This will accelerate advances in our understanding of the dollar spot pathosystem and assist in development of integrated programs for management of the most important turfgrass disease worldwide.
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