Winterkill and Recovery Update

Dr. Kevin W. Frank, Dr. J.M. Vargas, Jr., and Dr. Trey Rogers
Michigan State University

In the last couple weeks the extent of winterkill to Poa annua putting greens throughout mid to southeast Michigan has become evident.  On many greens we have observed several different colors of turf as winter receded and spring slowly arrived.  Generally the Poa annua that retained green color did of course survive and in many locations is now actively growing.  Poa annua that was brownish in color has slowly started to recover and our hope is that most of these areas will fill back in as temperatures and soil temperatures continue to warm.  The Poa that was white or dark gray to black does unfortunately appear to be dead.  Scratching at the turf or taking samples from these areas you may find some and I emphasize some, turf that has survived but to get these areas back in play will require seeding and/or sodding, and limiting traffic.

The different colors of winterkill.

Temporary Greens

One of the most common questions we have answered recently is if temporary greens are necessary.  Damaged putting greens will recover faster if temporary greens are used.  Traffic on Poa annua that is trying to recover or on newly seeded creeping bentgrass will lengthen the time for reestablishment and may even kill the new seedlings.  It is difficult to set a date for when damaged greens can be opened for play as Mother Nature reminded us again with snow and low temps this week that she is still in control.

Winterkill to Tees, Fairways, and Rough

Generally the damage to tees and fairways was not as severe as the damage to putting greens.  However perennial ryegrass, which is often used on driving range tees in Michigan, also suffered winterkill.  The good news with perennial ryegrass is due to its rapid germination and emergence; time for reestablishment should be shorter.     

Perennial ryegrass fairway test plot at HTRC sustained significant damage.

The rough on many golf courses was also damaged from snow mold activity.  Whereas greens, tees, and fairways are typically sprayed with snow mold fungicides to protect the turf, the rough typically not sprayed.  The rough will generally recover from any snow mold damage and in most situations won’t require any reseeding but limiting cart traffic in these areas is advised to allow recovery. 

Rough damaged by snow mold will recover but restricting traffic will help.

Reestablishment

Efforts to reestablish and recover winterkilled turfgrass are already underway on golf courses.  Many damaged greens have already been interseeded with creeping bentgrass and many more will be seeded in the coming days.  Sod from nursery greens on golf courses is also being used to patch small areas of dead turf. 

Surviving Poa annua emerging in verticut channels.

Spreading the Winterkill Message

In the last couple weeks I have conducted several radio interviews discussing winterkill on golf courses with the goal of explaining the issue and preaching patience from golfers.  One of the most recent was for the Greening of the Great Lakes radio segments that will air throughout the state this weekend.  You can listen to the interview by following this link (the audio is near the bottom of the article) http://goo.gl/93psbi

Winterkill 2014: What to do now

Dr. J.M. Vargas, Jr., Dr Kevin W. Frank, and Dr. Trey Rogers
Michigan State University

Winterkill 2014

In the last week as additional snowmelt has revealed the turf, it is now obvious that injury has occurred to annual bluegrass (Poa annua) in Michigan.  Most of the damage appears to be from ice cover that trapped toxic gases under the ice, which covered the greens for more than 45 days.  Many putting greens were under ice for 70 or more days.  In addition to ice cover, damage may also have been caused by crown hydration freeze injury, desiccation, and low temperature kill.  The questions now are primarily related to reestablishment.  Decisions would be easier if we could accurately predict the weather, but forecasts tend to lack accuracy and reliability.  If a warm spring occurs, interseeding the damaged areas with creeping bentgrass will work well. However, if a cold spring occurs, which many are predicting, it will take the interseeded areas considerable time to fill in with dense turf.  Sodding completely dead areas especially if you have an annual bluegrass nursery green may be a better option.  If you purchase sod, make sure your putting green root zone is compatible with the purchased sod root zone. However, if a nursery green is not available then seeding with creeping bentgrass is the only realistic option.   

Winterkill damage on a Poa annua putting green.

Interseeding Greens

The areas to be seeded on greens should be vertically mowed and if possible aerified, then seeded and lightly top dressed. The seed should be applied to the greens following aerification and then vertically mowed in an attempt to move the seed into the verticut slits. Another option would be to apply the seed to the greens and then run a spiker over the greens to push the seed into the soil. The aerification, verticuting and spiking should also stimulate some of the annual bluegrass seed reservoir in the soil to germinate as well.  A fertilizer with phosphorus should be applied at the time of seeding to encourage germination followed by light sand topdressing and rolling.  Research conducted on turfgrass reestablishment following winterkill at MSU indicates regular applications of fertilizer containing phosphorus results in faster establishment than nitrogen applications alone.  Foliar feeding is the preferred method of fertilizing since the cool soil temperatures and the limited root systems of the newly germinated seedling are not conducive to nutrient up take.  On ”warm” windy days, frequent light irrigation cycles will be necessary to keep the surface of the greens moist during the germination process and the earlier seedling stage.  Mowing heights should be raised to .150 in. and then gradually brought down to more normal mowing heights.  Based on our research mowing can begin 8-10 days after germination (covers will speed this up).  Do not be afraid to mow frequently in the beginning, as it helps the new seedlings establish.

Prepping a seedbed in a dead green.

Covers and diseases

If covers are available, they should be used on severely damaged greens. This will increase temperatures, especially on warm sunny days, and speed up the recovery process. Cotton grow covers can be cut into smaller pieces and used on greens that have small damaged areas allowing the green to remain in play. If covers are used on greens with major damage, temporary greens will have to be established.  Once sufficient establishment has occurred, the covers can be removed during the day to allow play to occur on the greens. At night the greens should be covered to retain the heat of the day and to further encourage as much growth as possible.  Microdochium patch fungicides should be applied to prevent this disease from developing, especially if covers are used. The QoI or dicarboximide fungicides would be good choices for management of this disease.

Covering greens may be critical for speeding reestablishment.