Golf Course Industry talked with Dr. Paul Koch, assistant professor, Department of Plant Pathology, University of Wisconsin-Madison, about what superintendents should know about snow mold as they plan their budgeting and ordering of control products.
What can you tell us about the different snow molds?
Gray snow mold (Typhula incarnata) is most likely to show up where there is snow cover of 60 days or more. Speckled snow mold (Typhula ishikariensis) is most likely to show up when there is snow cover for 90 days or longer. Pink snow mold (Microdochium nivale) does not require snow, just cool and wet weather. One of the ways to differentiate is to look for sclerotia, which are small, hardened masses of mycelium that act as the long-term survival structures of the fungus. If there is a pink or reddish ring around the outside of the diseased area and no sclerotia, it is probably pink snow mold. The sclerotia for gray snow mold are embedded in the leaf tissue and are relatively large and red. Those of speckled snow mold are also embedded in the leaf and sheath tissue and are smaller and black in color.
If they are different, do they need different controls?
They are not necessarily controlled by the same fungicides, but you can have all three snow molds in the same spot, especially in the areas prone to extended snow cover. Previous years of snow mold damage can increase the chance you will have snow mold this year because of an increase in the amount of inoculum present. Even if you have controlled snow mold for years, spores and mycelium can blow in from nearby locations. In regions with harsh winters, our research has shown that two or three fungicides with various modes of action are required for acceptable control. In regions with less severe winters, fungicide selection will depend on traditional amounts of snow mold observed, the course expectations, and the financial capabilities of the club. Some courses can get by with light or no applications on fairways if they can tolerate some damage.
What about timing for application?
Timing is rather critical. You obviously want the product down before snow cover, but you also don’t want it down too soon because of the risk of fungicide degradation prior to snow cover. Our research has shown that sunlight doesn’t lead to breakdown of snow mold fungicides, however rain and warm temperatures can result in drastic reductions in concentration in a short period of time. If you have a significant rain after application and/or an extended period of no snow cover and warm temperatures you may be susceptible to disease breakthrough over the course of the winter, you may have breakthrough. You may want to consider another application, especially in the areas expected to look their best. There are no black and white dates for application. Superintendents just need to use a combination of past history and weather forecasts to attempt to determine the best possible timing.
Are there any cultural practices that might help?
As always, healthy turf is best. Research out of Cornell and Wisconsin has shown that higher potassium levels can increase both gray and pink snow mold, so it may be beneficial to lower potassium levels in the soil. You also don’t want lush green growth going into winter. We don’t like to see late season N applications and also recommend leveling off the N by the end of September. Raising the cutting height by even nominal amounts in the fall will help the plant prepare for winter, as will ensuring proper drainage and air movement/sunlight penetration.
