PUYALLUP, Wash. – Two years ago, yellow, orange, and bronze circular patches began mysteriously marring the emerald-green turf of numerous putting greens on golf courses in western Washington, Oregon, and British Columbia. All told, the courses lost $500,000 in grass and greens from Everett, Washington, to Portland, Oregon.
Green keepers sent samples of the dead or dying turfgrass to the Washington State University Plant Diagnostic Clinic in Puyallup for answers. Diagnostician Jenny Glass found spores of a familiar water mold with an elegant name: Pythium. But which one of more than 150 species of Pythium?
WSU turgrass expert Dr. Gwen Stahnke

“The presence of Pythium hasn’t really changed; it exists in the soil in some unknown quantity,” said WSU turfgrass science graduate student Nathan Stacey. “From a diagnostic perspective, Pythium spores in samples would indicate Pythium activity. The problem is that there are numerous Pythium species. We’re trying to isolate the species of Pythium that caused the decline in turfgrass.”

Last October, the WSU Puyallup Research and Extension Center, Northwest Turfgrass Association, and Washington State Commission on Pesticide Registration teamed up to investigate the problem. Stacey, Glass, Drs. Marianne Elliott and Gwen Stahnke, and scientific assistant Katie Coats collected 50 samples from 27 Pacific Northwest golf courses during the fall, winter, and early spring. Most of the samples were isolated from annual bluegrass, the predominant putting-surface turfgrass species.
The researchers presented their initial findings during the 2011 WSU Turfgrass Field Day July 19 in Puyallup.
So far, Pythium torulosum, Pythium vanterpoolii, and Pythium volutum have been identified as the most common species in the golf course samples. Stacey and the team will continue to culture and sequence all samples, then determine if the pathogens are infectious by reinfecting turfgrass under varying conditions of shade, moisture, and soil temperature.
“Why did it happen? I think that question will be answered once we determine what we’re dealing with,” Stacey said.
Pythium Puzzlement Keeps Turfgrass Managers Sleepless
Field day speaker Dr. Jim Kerns

Diseases caused by Pythium are as effective as No-Doz® for keeping golf course supervisors awake at night, according to Jim Kerns, the field day’s featured speaker. Some have even blamed this kissing cousin to a fungus for wiping out entire fairways overnight.

Kerns, an assistant professor and Extension specialist of turfgrass pathology at the University of Wisconsin at Madison, broke down three main Pythium diseases for 50 to 60 attendees. The species that causes Pythium blight attacks above-ground foliage; those responsible for Pythium root rot destroy the root system. Still other species cause Pythium root dysfunction, another disease similar to root rot. Control measures are different for each species; a fungicide that works well to treat blight won’t work with root rot, making disease management a challenge. Since Pythium likes warm, wet conditions, cultural practices are also effective in fighting it, including limiting irrigation and increasing mowing height.
“Pythium diseases, especially those that affect the roots, can be very difficult to diagnose in the field,” Kerns said. “Therefore, if symptoms or signs develop that are characteristic of these three diseases, submit samples to a local diagnostic clinic immediately. The best way to combat these diseases is to know which one you are dealing with.”