Brown ring patch

The fungus causing brown ring patch, Waitea circinata var. circinata, was first identified in Japan in 2005 damaging creeping bentgrass. The disease was thought to be restricted to Japan until its first report in the United States in 2007 infecting annual bluegrass.
There is typically a period of six weeks or more between first infection of the roots and the presentation of symptoms. The disease causes circular or scalloped rings in the turf up to 1 metre (3.3 ft) in diameter, with the width of the ring itself being up to 3 centimetres (1.2 in). The rings turn from yellow to light or reddish brown as the disease progresses. The disease is most noticeable on putting greens and commonly occurs in the spring with rising temperatures. Brown Ring Patch is similar to other Rhizoctoniaspecies, but appears to infect upper roots, crowns, and stems as well as foliage of individual plants. It also degrades thatch, gives rise to sunken rings, and acts somewhat like superficial fairy ring.