The life of a golf course superintendent is a constant journey, traveling along from one challenge to the next. One day, it might be hauling out greens covers to protect against winter damage, the next it could be getting a jump on disease control in advance of the next playing season.
Dollar spot is one of the most common diseases superintendents encounter. It is most active when temperatures are between about 60 and 90 degrees Fahrenheit. That is a pretty big window of opportunity for the pathogens in genus Clarireedia that cause the disease and a big window for guesswork on the part of turf managers.
The Smith-Kerns Dollar Spot Prediction Model developed at the University of Wisconsin can help superintendents identify periods when dollar spot is most likely to occur. Developed by Damon Smith, Ph.D., and Jim Kerns, Ph.D., the model that bears their name uses a five-day average of daily humidity and average air temperature that superintendents then can use to accurately time spraying for dollar spot control. According to the University of Wisconsin, the model was developed using years of research conducted in Wisconsin, Connecticut, Mississippi, New Jersey, Oklahoma, Pennsylvania and Tennessee.
Users must determine a spray threshold unique to their property and turf type and a fungicide reapplication interval. For example, at the University of Wisconsin, the researchers determined that a threshold of 20 percent provided acceptable disease suppression on creeping bentgrass. That level can vary based on turf type, cultural practices, environmental conditions and climate.
Once the application interval has been reached and conditions (theoretically) change, the model should be run again to help the superintendent determine the next application period.
The model is the result of a complex mathematical equation that is described in-depth in this peer-reviewed document.
Users can use excel documents to upload weather data either in degrees Fahrenheit or degrees Celsius. Data also can be uploaded for users in select states through the Michigan State University Growing Degree Day Tracker and the Greenkeeper App developed by Bill Kreuser, Ph.D., at the University of Nebraska.
Syngenta also has recently enhanced its dollar spot alert system that is based on the Smith-Kerns model. The Syngenta system provides season-long text and email notifications along with the ability to forecast disease development risk five days into the future. Superintendents can sign up at GreenCastOnline.com/DollarSpot to be notified by email or text, when conditions in their area are conducive to dollar spot development.
Once a superintendent registers they will receive their first notification of the season when dollar spot pressure in their area based on the 20 percent threshold level described above, which will help them prepare for a preventive fungicide application. After the first alert, superintendents can also elect to be notified of their dollar spot risk on 7-, 14-, 21- or 28-day intervals.