The recent wet weather during the past couple of weeks followed by “August” in June weather has led to Pythium root rot from the Piedmont to the Coast on creeping bentgrass putting greens. This is not to be confused with Pythium root dysfunction (Pythium volutum). Pythium root rot has been the most diagnosed disease in the Turfgrass Diagnostics Lab over the past 7-10 days on creeping bentgrass samples.
The symptoms of Pythium root rot are typically very irregular in shape and tend to have no set pattern about the distribution, however a patch type symptom may be observed on occasion. These affected areas often start out looking orange and/or yellow and turn brown and/or tan rapidly. Although damage is usually worse in poorly drained or low lying portions of a green, it is not limited to those areas and can even be found on humps and ridges.
Fungicides are available for Pythium root rot control, and should be applied prior to forecasted wet periods or shortly there after. Just remember that when applying fungicides for Pythium root rot you will need to water the product in to the depth of your root system, which can vary greatly from course to course.
For More Information: Pythium Root Rot
Source: Lawn Disease Alert: Pythium Root Rot