Perspectives Online

Making turf Tiger-worthy: College researchers identify pathogenic pests threatening putting greens

Keeping golf course greens and fairways green and fair is a goal of crop scientist Fred Yelverton (left), entomologist Rick Brandenburg (right).
Photo by Becky Kirkland

College of Agriculture and Life Sciences researchers had a hand this spring in helping prepare Pinehurst Resort's Course No. 2 for the recent U.S. Open. If the headlines are any indication, they did a good job: "Course wows players: No. 2 in 'Incredible Condition' as Top Golfers Prepare to Put on U.S. Open Show," shouted a Raleigh News & Observer sports headline over a photo of PGA Tour legend Tiger Woods.

But that's only one aspect of the efforts on the part of researchers from the three departments to help identify and get one golf-course-related turfgrass problem under control.

Before the Open, Pinehurst 2, as well as many other Southeastern golf courses, most built in the past six years, suffered from what Dr. Lane Tredway calls unusual - you might even say mysterious - disease problems on their creeping bentgrass putting greens. The affected greens showed circular patches from three inches to several feet wide in which the grass was turning yellow-to-orange in late spring and early summer.

"Pinehurst had some problems with this disease we've now identified as Pythium root dysfunction, but they have kept it well under control," says Tredway, an assistant professor and Extension specialist in the College's Department of Plant Pathology. "Using information from research by my graduate student James Kerns on one of Pinehurst's practice greens, we can help golf course superintendents all over North Carolina to develop safe and effective disease control programs."

Tredway, who specializes in turfgrass management, works with Extension specialists Dr. Fred Yelverton, professor in the Department of Crop Science, and Dr. Rick Brandenburg, professor in the Department of Entomology, to help Pinehurst golf course superintendents.

"Our research is not a one-way street," Tredway says. "While the course superintendents rely on us for research-based information, we learn a great deal from them based on their experiences and daily observations."

Plant pathologist Lane Tredway.
Photo by Becky Kirkland
The researchers' work is high-impact. They don't call those putting surfaces "greens" for no reason - and they're not worth much if they're brown. Since maintenance on our state's 2.1 million turfgrass acres alone generates $833 million annually, turfgrass problems affect North Carolina's economy.

Identifying and controlling root dysfunction presented unique problems.

According to Kerns' and Treadway's research, this disease has been very difficult to characterize. "In fact, we have been unable to consistently isolate any pathogens from the affected turf during summer when the symptoms are most common," Kerns says.

Observed as early as four months after seeding of newly constructed greens on most of the new-generation creeping bentgrass varieties, the disease doesn't seem to be as influenced by soil pH as are some pathogens. Most of its growth and root damage appears to occur during the fall and spring when creeping bentgrass roots are actively growing. According to a Plant Pathology Department crop profile, North Carolina is in a transition zone, where both cool-season and warm-season turf species can grow. However, heat tolerance of cool-season species and cold tolerance of warm-season species is an issue for the state's turf managers.

After unusually warm, dry weather in 2003 and 2004, mild symptoms of the then-unidentified disease recurred in several locations. The symptoms were consistent with a disease described in 1985 as one found on newly constructed bentgrass putting greens in Iowa, Tredway says.

College researchers, however, consistently isolated two other pathogens, P. volutum and P. torulosum from roots exhibiting symptoms of Pythium root dysfunction in fall of 2003 and spring 2004. The former, known to be very aggressive toward creeping bentgrass seedlings at cool temperatures, was dominant in every experimental location; the latter present in only half.

This led researchers to suspect that the more widely distributed disease - Pythium root dysfunction - is caused by P. volutum.

But the pathogen can be controlled. "Based on our observations, cultural management practices have a major impact on the development and severity of this disease," says Kerns.

Due to ongoing studies such as Kerns' at Pinehurst, researchers have developed effective fungicide programs to control the suspected Pythium disease after Tredway and Kerns found that standard Pythium fungicides weren't as effective as expected in 2003 research trials. But by 2004, they had found a fungicide that seems to curb the problem for almost a month.

Nevertheless, says Kerns, more questions than answers remain related to the suspected Pythium root disease.

The researchers are certain, however, that continuing research should provide answers and provide golf course superintendents with accurate methods to diagnose and manage root diseases in creeping bentgrass.

- Art Latham

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