Sclerotium rolfsii Spotted at the ISU Horticulture Research Station

July 25, 2013

This spring, as you all know, brought large amounts of rainfall to central Iowa. This was a blessing for most including us the Horticulture Research Station. The water level in the pond returned to its maximum height, soil moisture reached great depths, and reduced the amount water needed to irrigate. The record breaking rainfalls also encouraged moss growth on one of our putting greens. Over the years, we have tried to encourage this growth to continue research on moss controls.

A couple of weeks ago, I noticed spots on the green that appeared to look like dollar spot, however, the spots were only covering the moss and not the bentgrass. I decided to leave the area untreated to see if these spots would continue to spread or remain localized. Within a few short weeks, the disease spread like wildfire across the moss. A sample was taken to the Disease Diagnostic Clinic here at Iowa State University. The pathogen was identified as Sclerotium rolfsii.


Sclerotium rolfsii is a fungal disease that has an extensive host range that targets over 500 species. It is very common in the tropics, subtropics, and other warm temperature regions. However, it is very rare to see the disease this far north. The pathogen rarely occurs when winter temperatures fall below 32˚F. The disease survives in the form of sclerotia. These sclerotia are easily spread by foot traffic and mowing equipment. Most of the research articles that I have read state that control is relatively difficult to achieve. We will continue to monitor the area and post any updates on the control.