Powdery mildew is caused by an obligate parasite which survives on the surface of the turf.
The body, or mycelium, of the fungus appears as a white powdery substance which can easily be scraped off the surface. The disease can occur throughout the growing season but is most typically seen on Kentucky bluegrass in moderate to severely shaded conditions. It is not present on most athletic fields but is often found near bleachers and buildings. No chemicals should be used to manage the disease as it is almost always a cosmetic disease and rarely kills turf.