Yellow Patch and Brown Ring Patch
The appearance of yellow to reddish brown rings is a common springtime occurrence on golf course turf. Fortunately, it appears in most cases these yellow rings are gone by Memorial Day.
Yellow Patch, or cool temperature brown patch is often associated with these rings that occur on creeping bentgrass (Agrostis stolonifera) and perennial ryegrass (Lolium perenne), but the symptoms are most widespread on Poa annua. The patches can range from circular to irregular or scallop shaped ranging from 1 to 3 feet in diameter. The yellow ring along the circumference of the patch ranges from one-half/ to an inch in width. Yellow patch,caused by the pathogen Rhizoctonia cerealis, occurs under cool (50 to 65 F) wet cloudy conditions. The disease is normally considered a minor problem because with the arrival of warmer sunny conditions the symptoms disappeared.
If daytime temperature increase (80s) and the yellow rings persist the likelihood of brown ring patch being the culprit increases. The brown ring patch pathogen was initially described as “Rhizoctonia-like”. Researchers at the University of California, Riverside identified the pathogen as Waitea circinata. Previously, researchers in Japan identified the same pathogen as causing similar symptoms on creeping bentgrass and named the disease “brown ring patch” .