Diseases of cool season turfgrasses (
Pythium blight
Pythium blight, caused by Pythium aphanidermatum, usually attacks creeping bentgrass (Agrostis palustris), Kentucky bluegrass (Poa pratensis) and ryegrass (Lolium sp.). The disease occurs during the hottest summer months, especially during the monsoon season, and also can be prevalent on ryegrass used to overseed hybrid bermuda grass in September and October in the central and southern parts of Arizona. During the summer of 2000, the disease was particularly devastating to bluegrass and ryegrass grown in the transition areas of the state.
Symptoms include wilted (blue/gray) and matted turf, often with a greasy appearance. White mycelium can often be seen at the advancing margin of the disease, especially in the early morning (photo link). As disease progresses, large areas of turfgrass may be destroyed in as little as twenty-four hours.
Pythium aphanidermatum is a zoosporic plant pathogen and as such has a motile stage. This facilitates the rapid progression of the disease especially in extremely wet conditions. Salinity also may be a factor in disease development. When creeping bentgrass and Poa trivialis are irrigated with elevated salinity water, disease progresses much more rapidly than with tap (low salinity) water. This has been observed in the field and deomonstrated in laboratory trials (photo 1). Over-watering must be avoided. Fungicides such as mefenoxam, azoxystrobin, pyraclostrobin, mancozeb and foetyl-Al are effective in controlling Pythium.
1
For more information:
http://www.oznet.k-state.edu/path-ext/factSheets/Turf/PythiumBlightofTurfgrasses2.asp
December 26, 2006