Pythium Blight

Grass Affected

Cool-season grasses mostly, bermudagrass is slightly susceptible.


Diagnostic Description

  • First appears as dark, greasy, matted together spots in irregular patches up to several inches across. Cotton-like webbing may appear in early morning when heavy dews are present. Following drying, mycelium disappears and the dry grass blades turn reddish-brown.
  • Diseased areas may grow together into streaks a foot or more long where the fungus is carried by surface water or tracked by mowers. In late stages, the disease can spread very quickly on all plants and an infected area usually is killed.



Conditions Favoring Infestation and Typically Yearly Occurrence

Favored by high temperatures, excessive moisture, poorly drained soils, poor air circulation and high nitrogen fertilization. Late Spring, Summer, and Fall.