Yellow Patch

Yellow patch (or commonly referred to as cool season brown patch) is identified by small to medium patches that appear as yellow to rusty-red rings or arc-like patterns ranging in size from a few inches to several feet. Yellow patch is a cool season disease with symptoms that occur from October through late April. When seen in the early stages, yellow patch is most noticeable early in the morning but difficult to see by midday. Infected plants exhibit a light, water-soaked lesion at the base of the leaf sheaf or in the crown tissue.

A growth of mycelium may be visible early in the part of the day when dew is present. The fungus survives in the soil as bulbils. Bulbils are initially light colored, then dark brown when mature. The pinhead-sized bulbils can be numerous in the thatch surrounding damaged turfgrass.

The rings are most prevalent in the early spring, because they contrast sharply with newly emerging leaves. In most cases, the symptoms remain superficial, with rings that are difficult to see. Infected plants recover quickly when temperatures increase. During prolonged cool, wet periods in late winter to early spring, patches can become necrotic and sunken. These damaged areas do not recover quickly.
Conditions

Yellow patch development is favored by extended periods of wet, cloudy weather. It is a cool-temperature disease (50 to 65 degrees F). Disease development is greatly suppressed at temperatures lower than 45 degrees F and greater than 75 degrees. Yellow patch tends to be more severe on putting greens with poor subsurface drainage.
Management

Yellow patch control is not normally recommended, because the disease symptoms are so short-lived. Core cultivation in the fall can help reduce disease severity by improving the infiltration rate. Although there is no direct evidence that high nitrogen rates increase disease severity, avoid excessive nitrogen fertilization in the fall. Yellow patch symptoms are generally superficial and will not require a targeted fungicide application. If you decide that fungicide is needed as an option, then look toward strobilurin products. Please speak with your local chemical representative or local university extension office for future help.