The Importance of Fall Practices to Reduce the Potential for Microdochium Patch
With the arrival of cool wet conditions of fall and early winter, Microdochium patch becomes a disease issue throughout the temperate region. 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 golf courses where annual bluegrass predominates especially in shaded, wet, north facing areas. On higher cut turf like home lawns and athletic fields, perennial ryegrass and Kentucky bluegrass are susceptible to Microdochium patch. And in general, young, juvenile or lush turf is more susceptible then mature stands.
Figure 1. Microdochium patch symptoms on a putting green in early spring. The patches are roughly 12-inches in diameter.
Microdochium patches initially appear as small patches, maybe 1 to 2 inches in diameter that eventually reach 12-inches in diameter. Leaves become water soaked, turn reddish-brown then turn a bleach color. In cool wet weather, the leaves are matted together, which is especially true on high cut turf, and covered with a whitish pink mycelial growth that is slimy when wet. The pink mycelium is often observed in the early morning. The circular patches may exhibit a pink coloration when exposed to light.
Figure 2. The initial symptom of Microdochium is a spot that is normally 1-inch in diameter.
On higher cut turf like lawns, cultural practices can help reduce the severity of Microdochium patch. Given that matted turf is more prone to Microdochium patch, continue to mow regularly until the turf ceases growth. Mulching or removing leaves from the turf can help reduce a wet moist environment for the disease to develop under the leaf cover. Late season fertilization should be timed correctly. If the timing is incorrect, the potential for lush growth increases which will increase the potential for Microdochium patch. As a general rule the late season fertilization application should be made when the turf is still green but not growing. This time should correspond when clippings are no longer occurring with mowing.
Figure 3. In some instances a pinkish border is visiable around the outer edge of the patch.
On low cut high quality turf Microdochium patch may require fungicide applications to prevent turf loss. There are several fungicides available that can control Microdochium patch. Some of those fungicides can be found on the Snow Mold Assurance sheet. The most effective timing for Microdochium patch is preventatively. In areas where Microdochium patch is a serious problem the first application is especially important. The pathogen, Microdochium nivale, is a prolific spore producer and a properly timed preventative application (watch the weather!) is an effective means of suppressing spore populations.
Figure 4. Microdochium patch symptoms on a higher cut turf (picture taken in the spring).
About the author
Dr. Karl Danneberger is a professor of Turfgrass Science at The Ohio State University. Dr. Danneberger's contact information can be found here. You may also follow Dr. Danneberger on Twitter: