Cool season brown patch
Yellow patch, also known as cool season brown-patch, is a Rhizoctonia pathogen similar to that of brown patch. Symptoms first appear as smaller (6-12 inches in diameter) patches, with yellow margins. Damage occurs on creeping bentgrass and annual bluegrass putting greens, and is typically a cosmetically damaging disease which does not cause severe turf damage. Individual patches may coalesce to form large irregularly shaped yellow areas.
Yellow patch is most prevalent in the early to mid-spring, and can also occur in mid-fall. Outbreaks occur on cool season turfgrasses during extended periods of cool, cloudy, wet weather. The fungus is most active between 50° F and 75° F.