Figure 1

Since 2002, many golf course superintendents in the southeastern United States have reported unusual patches appearing on their creeping bentgrass greens. Symptoms appeared during the heat of summer in irregular patches ranging from 6 inches to 12 inches in diameter. Grass in affected areas was initially wilted and chlorotic, but later exhibited a yellow to orange foliar decline. The patches resemble the stand symptoms of take-all patch (Figure 1), and microscopic examination of affected tissue revealed necrotic crowns, which is another symptom of take-all patch.

Figure 2

As a result, many pathologists, ourselves included, diagnosed the problem as take-all patch. Yet, the fungicides typically used for take-all patch were not effective against the disease. Furthermore, isolations revealed that the take-all pathogen was not present in the affected areas.

Figure 3

It was not until the fall of 2003 and spring of 2004 that we discovered another pathogen in the infected root tissue. During this period of unseasonably hot, dry weather, we found an abundance of Pythium hyphae, oospores, and sporangia (Figure 2) in the root tissue. Furthermore, examination of affected root tissue revealed bulbous root tips, loose cortical structure, and an absence of root hairs (Figure 3). To our fortune, we found two papers by Clinton Hodges at Iowa State published in the mid-1980s that described very similar symptoms. Hodges observed that two Pythium species, P. aristosporum and P. arrhenomanes, were associated with irregular patches and roots that were tan-colored, devoid of root hairs, lacked cortical structure, and possessed dead bulbous root tips. Hodges coined the disease Pythium root dysfunction (PRD) because there was no apparent rotting of the roots, and the root tissue was not functioning properly.

Quick Tip

Pythium root dysfunction also was observed by Feng and Dernoeden in Maryland in 1999. They collected 28 isolates from 109 putting green samples exhibiting symptoms of Pythium root dysfunction and identified eight different Pythium species. The researchers concluded that P. aristosporum was the most important causal agent of PRD based on frequency of isolation and aggressiveness toward creeping bentgrass seedlings. Following these accounts of PRD, little work has been conducted on this disease. Therefore, very little is known about the etiology, epidemiology and management of PRD. Our work at North Carolina State University has focused on the etiology and epidemiology of PRD in order to develop effective management strategies for superintendents.