Dollar spot

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Dollarspot

Dollar spot is a common turfgrass disease affecting golf courses, lawns, and other areas where grass is maintained for aesthetic or recreational purposes. The disease is caused by the fungus Sclerotinia homoeocarpa. It is named for the silver dollar-sized spots (typically 2-6 inches in diameter) that appear on the affected grass. These spots can coalesce into larger patches if left untreated, significantly impacting the appearance and health of the turf.

Symptoms and Identification

The primary symptom of dollar spot is the appearance of small, circular, straw-colored patches on the turf, which are roughly the size of a silver dollar. Upon closer inspection, leaves within these patches exhibit lesions that are bleached-white to straw-colored, often with a reddish-brown border. The disease is most active during periods of high humidity and moderate temperatures, particularly when night temperatures are between 60-70°F (15-21°C) and day temperatures are between 70-85°F (21-29°C).

Causes and Conditions

Dollar spot thrives in conditions of high humidity, low nitrogen levels, and when the turf is under moisture stress. The fungus Sclerotinia homoeocarpa infects the leaf tissue of the grass, disrupting the normal function and appearance of the turf. The disease cycle can be exacerbated by poor air circulation, excessive thatch, dew presence, and improper irrigation practices.

Management and Control

Effective management of dollar spot involves a combination of cultural and chemical strategies. Culturally, maintaining adequate nitrogen levels through fertilization can help prevent outbreaks. Proper irrigation practices, such as watering deeply and infrequently to avoid prolonged leaf wetness, are crucial. Regular mowing and dethatching can improve air circulation around the turf and reduce the humidity microclimate that favors the disease.

Chemical control includes the application of fungicides. These should be used as part of an integrated pest management (IPM) approach, considering the specific conditions and susceptibility of the turfgrass in question. Fungicide applications may be necessary during periods of high disease pressure, especially when environmental conditions are conducive to the spread of the disease.

Cultural Significance

Dollar spot is of particular concern in the golf industry, where the appearance and playability of greens, fairways, and tees are paramount. It can also affect homeowners who take pride in maintaining a healthy, aesthetically pleasing lawn. The disease represents not only a visual problem but also a potential economic burden due to the cost of fungicides and the labor involved in applying treatments and implementing cultural control measures.

Research and Future Directions

Research into dollar spot continues to focus on understanding the biology of Sclerotinia homoeocarpa, developing resistant turfgrass varieties, and improving fungicide application techniques. Advances in genetic research may offer new insights into disease resistance, while integrated pest management strategies continue to evolve to reduce reliance on chemical controls.

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