Yellow Patch

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Yellow rings are the predominant symptom of yellow patch in annual bluegrass greens. Courtesy of S. McDonald

Reddish-brown ring symptoms of yellow patch in creeping bentgrass. Courtesy of Pete Dernoeden, Ph.D.

Causal Agent:

Rhizoctonia cerealis

Susceptible Turfgrasses:

Annual bluegrass; Creeping bentgrass

Symptoms:

The most common symptom of yellow patch is the appearance of yellow rings a few inches to over a foot in diameter. Rings may be solitary or numerous. Less commonly, solid yellow patches or reddishbrown rings develop. Reddish-brown rings are more common in bentgrass and may loop together like those on the "Olympic" flag. There are no distinctive leaf lesions and foliar mycelium seldom develop. Damage usually is superficial and affected plants normally recover with the advent of sunny and dry weather. This disease is very similar in appearance to Waitea patch (aka brown ring patch); which occurs during warm and rainy periods in mid-to-late spring.

Conditions Favoring Disease:

Yellow patch occurs from fall to spring during extended overcast, rainy and chilly (50° to 65°F) weather. The disease is most severe when thatch is cold and wet for long periods.

Management Tips:

Improve soil and surface water drainage.
Reduce shade and increase air circulation.
Apply small amounts of nitrogen (~ 0.25 lb N/1,000 ft²) to promote recovery when turf begins growth in spring.
Use a proper fungicide preventively in late fall/early spring where yellow patch is a chronic problem.
Curatively, apply a proper contact fungicide plus a systemic fungicide, but don’t expect rings and patches to recover until sunny and dry conditions recur.

Frequently occurs in:

In all cool-humid regions.