Dollar spot is a turf disease that can strike cool-season and warm-season grasses alike. To help properly treat dollar spot, Landscape Management spoke with Brian Aynardi, Ph.D., Northeast research and development scientist with PBI-Gordon; Mike Agnew, Ph.D., technical services manager with Syngenta; and Ian Rodriguez, Ph.D., technical services manager for Quali-Pro.

DO

DO USE A DISEASE MODEL. “Keep an eye on the weather forecast and use the Smith-Kerns Dollar Spot Prediction model. Any time warm daytime temps, high relative humidity, cloudiness and cool night temperatures are predicted, the dollar spot pathogen is likely to be active. Even if preventive applications are not desired by clients, following the weather will allow turfgrass managers to scout in a timely manner and look for the first signs (aerial mycelia) of the pathogen and symptoms (tan lesions with brown borders) of the disease so that they can convey the need for a fungicide application to the client.” – Aynardi

DO FOCUS ON FERTILITY. “Maintaining a steady nitrogen supply during the season is important to avoid the issue. There are some very good, slow-release fertilizer technologies readily available to lawn care operators today that can be an effective approach without requiring frequent applications.” – Rodriguez

DO READ LABELS. “There are a number of fungicides listed for dollar spot control. Some fungicides may only be listed for commercial landscapes, so take care to review labels for proper use locations prior to application. Representative fungicide groups are the succinate dehydrogenase inhibitors, demethylation inhibitors and benzimidazoles. Active ingredients labeled for residential and commercial applications are isofetamid, myclobutanil and thiophanate-methyl.” – Aynardi

DO REDUCE THATCH. “Reducing thatch by lawn aeration or dethatching will be beneficial in the long run by preventing much of the root system growing in the thatch layer. Irrigate the lawn frequently enough to maintain good soil moisture when the disease is active.” – Agnew

DO THINK ABOUT PREVENTION. “Make preventive applications, which may work significantly better than curative applications.” – Agnew

DON’T

DON’T NEGLECT CULTURAL PRACTICES. “Cultural practices are typically a means of prevention rather than a curative approach.” – Rodriguez

DON’T WATER AT NIGHT. “Excessive leaf moisture that persists for an extended period of time is critical in the disease cycle of a variety of turf pathogens. Secondary to this would be areas that see minimal sunlight due to tree and shrub growth and have minimal air movement for the same reason. These areas do not dry out as well as the rest of the lawn, and as a consequence, pathogens are first noticed in these locations.” – Aynardi

DON’T JUST BLAME FERTILITY. “Dollar spot is frequently described as a disease of poorly nourished turf. However, when a susceptible turfgrass cultivar is present, dollar spot can be destructive even if the lawn receives adequate fertility.” – Agnew

DON’T WAIT. “Whenever possible, chemical applications should be deployed prior to disease development. Cultural strategies should be employed throughout the growing season, but proper fertility and attempts to increase air movement should be in place by the time environmental conditions are conducive for disease development.” – Aynardi

DON’T PANIC. “In the case of dollar spot, most healthy lawns can tolerate or simply outgrow the damage caused by the disease so that it does not reduce the aesthetic value.” – Rodriguez