Winterkill Update Spring 2015

Dr. Kevin W. Frank and Dr. Joe Vargas, Jr.
Michigan State University

The winter of 2013-2014 produced devastating levels of winterkill, especially in the Detroit area.  As a result of the damage experienced to Poa annua putting greens last year golf course superintendents devised plans for this winter to reduce the potential for winterkill including using different cover systems and in some instances actively removing snow events to prevent any possibility of ice forming on putting greens.  Despite all of these efforts it appears that once again this spring Poa annua putting greens have been damaged.  Although the damage I’ve observed this year doesn’t appear at this time to be as severe as in 2014, the geographic extent of the damage in Michigan appears larger.  Initial observations and reports from the field indicate damage extending from at least the Grand Rapids region through greater Detroit.  Damage once again may be attributed to ice sheets on putting greens.  Many golf courses report ice sheets that formed around January 1 and in some cases didn’t melt off until early March, approximately 60 days of ice cover.  The day estimates for Poa annua survival under ice range from 45 to 90 days and for creeping bentgrass from 90 to 120 days.  For the Poa annua greens the ice cover from this winter was definitely in the range when damage can occur.  There also may be damage due to low temperature kill and/or desiccation for greens that were exposed throughout winter.  Crown hydration freeze injury also appears to be evident on some greens especially in poorly draining areas, although this injury could also be from thicker ice sheets that formed early in winter in these depressions.  

Possible winterkill following surface drainage pattern.

Poa annua loses its cold temperature hardy proteins and begins to take up water quickly as temperatures warm in the spring.  As snow melts and water collects in low lying or poorly draining areas if the temperature drops below freezing and ice forms it can crush the swollen crowns of Poa annua plants killing them.  To date, determining the extent of damage has been difficult as temperatures have been very cold and very little turf growth has occurred.  Since the snow melted it has been a very dry spring, to facilitate recovery it would be a good idea to charge up the irrigation system so when the warmer weather arrives plants emerging from dormancy will have access to water.  If the weather forecast is correct, and warmer temperatures arrive next week assessing the extent of damage will be easier.