Winter Kill on Michigan Golf Courses

Winterkill damage on turfgrass
The past winter was no treat for turfgrass on golf courses in Michigan. Golf courses throughout the state have suffered from what is commonly referred to as winterkill. Winterkill is a general term that is used to define turf loss during the winter. The different types of winterkill include: crown hydration, desiccation, low temperature kill, ice sheets, and snow mold. Due to the unpredictability of environmental factors, and differences in other factors such as drainage, the occurrence of winterkill on golf courses is variable and can vary greatly between golf courses and even across the same golf course. The most common type of winterkill seen this year is from crown hydration injury and ice sheets trapping toxic gases. 

Crown Hydration Injury and Ice Sheets
Many annual bluegrass (Poa annua) greens and fairways suffered winterkill from crown hydration injury.  The problem occurs in late winter, when day time temperatures become warm enough that the annual bluegrass plant begins to take up water (hydrate).   During these thaw/freeze events, ice crystal formation can occur in the crown of the plant. Ice crystal formation will rupture the plant cells and ultimately cause the plant to die. However, there are other factors involved that we don’t understand. There is plenty of moisture in the entire green following snow melt, but the turf only dies where there is standing water.  This is an area we need to research when funds become available.    

Ice sheets that do not allow gases to escape can also result in the turf dying. There are two toxic gases principally responsible for this buildup, butanol (CH3CH2CH2OH) and ethyl butyrate (CH3CH2CH2CO2CH2CH3). As the ice sheet melts away, the area damaged closely mirrors where the ice was present. Often times if the ice is mechanically removed a foul odor caused by these gases is present.    

Winter desiccation is the death of leaves or plants by drying during winter when the plant is either dormant or semi-dormant. Desiccation injury is usually greatest on exposed or elevated sites and areas where surface runoff is great. This was not a serious problem this year.

Steps in Recovery
Reestablishing turfgrass in damaged areas can be very challenging in the spring due to cool, cloudy conditions that often persist. Depending on the extent of damage, either seeding or sodding can be used to facilitate recovery. In areas where the turf was killed in a manner that there are well-defined margins between dead and living turf, it may be feasible to strip dead turf and sod the area. In areas where the kill was more scattered it may be easier to seed the area. Seeding can be difficult, especially on damaged areas of greens. Inter-seeding creeping bentgrass into dead areas on the greens has given mixed results. The best results with inter-seeding have occurred when the low mow, high density type creeping bentgrasses, such as the Penn A and G series or T-1 and Alpha bentgrasses, have been used. Several methods may be used to reseed damaged areas. Verticutting followed by seeding, using a slit-seeder, or using tools like the job-saver aerator attachment, can all be successful.  The inter-seeding process should continue on a weekly basis until the damaged area has completely recovered. On greens that are predominantly annual bluegrass, often it is better to scratch the surface of the dead areas to allow the annual bluegrass to germinate and fill in the voids. Keys to success for renovating winterkilled areas are to divert traffic from newly seeded areas, apply a starter type fertilizer regularly using either a granular or foliar product, and syringe the turf in these areas to ensure that the seedbed or sod is moist throughout the establishment period. Although it is unpopular with golfers, in some situations it may be necessary to close and cover the greens to speed recovery or at least divert traffic from damaged areas of greens to facilitate recovery.