Cool Wet Conditions: Microdochium Patch
In the temperate regions of the world, winter weather conditions are often favorable for Microdochium patch. Microdochium patch, also known as fusarium patch and pink snow mold occurs under wet cool conditions (32 – 46 F). Although turf managers commonly know this disease as pink snow mold when it occurs under a snow cover, the official name is Microdochium patch (also formerly referred to as Fusarium patch). Microdochium patch is especially active on annual bluegrass in areas that are: in shade, wet, north facing, or have a history of the disease. Creeping bentgrass is also susceptible to pink snow mold but not to the same extent as annual bluegrass. Young, juvenile, or lush turf is more susceptible then mature stands.
Through the winter, pink snow mold symptoms usually appear as circular patches that tend to be tan or whitish and in some cases have a pinkish border. In late spring when temperatures range between the 40s and 60s F and abundant moisture is present, the pathogen becomes quite active. The pathogen produces spores that move in water along drainage patterns and can easily be tracked by mowers.
Symptoms initially appear as a yellowing of the infected turf area that progresses rapidly to a rusty, reddish, brown color. The source of spores is often from old patches that were on the turf in the winter or the thatch. When the disease occurs in late spring it is usually active for short periods of time so the patches are not as large, distinct, or well defined as in winter and makes diagnosis more difficult. With the return of warm and dry weather the turf will often recover rapidly.