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.

Ice and Poa Survival Update

Dr. Kevin W. Frank and Dr. J.M. Vargas, Jr.

The winter of 2013-2014 will be remembered for many years to come.  The ice storm of Dec. 21-22 knocked out power for thousands and coated everything, included exposed turf, in ice.  Following the ice storm there was a brief warm-up Dec. 28-29 immediately followed by a Polar Vortex, a blizzard, and then another brief warm-up from Jan. 10-13.  The weather events resulted in thick ice sheets forming on many putting greens with the most severe conditions appearing to be from the Lansing area eastward.

Ice from a putting green.

The primary cause of death to turfgrass under ice sheets is from oxygen depletion and toxic gas accumulation from soil microbial respiration.  The warmer the soil is when the ice forms the faster the oxygen is depleted by the microbes and the sooner toxic anaerobic gases like butanol and ethyl butyrate will form.  These gases are what superintendents often refer to as the smell of death and unfortunately many, including myself, have experienced this smell in the last week.  The day estimates for Poa annua survival under ice range from 45 to 90 days and for creeping bentgrass from 90 to 120 days.  Currently many putting greens have been covered in ice for greater than 60 days.  We have sampled Poa annua under a 2 inch ice sheet at the Hancock Turfgrass Research Center at MSU weekly for the last three weeks.  Last weeks samples from 58 days under ice (5 days after sampling) show that ½ of the plugs sampled appear to be dead but we will continue to monitor and sample.  Some superintendents have started reporting similar results in the last week.

Poa annua samples, 58 days under ice, 5 days after sampling.

Many superintendents have been active in trying to clear snow and remove ice throughout the winter but it has been a nearly impossible process due to frequent snowfall and very cold temperatures that make melting or physically removing ice very difficult.  This might be the winter that Mother Nature dictates turf life and death no matter what actions were taken by superintendents.  Unfortunately winter is not over and the upcoming warm temperatures and melt that will arrive can be just as calamitous especially to Poa annua greens.  Poa annua loses its cold temperature hardy proteins and begins to take up water quickly as temperatures warm.  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.  The damage resulting from freeze/thaw cycles is typically referred to as crown hydration injury.  Despite efforts to squeegee water from low spots on greens it is difficult to remove all the water and completely prevent crown hydration injury.  It has already been a very taxing winter and unfortunately spring doesn't look like it will be any easier.  We will continue to update the situation as spring arrives.

Melting Ice Sheets on Greens

Dr. Kevin W. Frank, Michigan State University

Andrew Hollman, Dr. Brian Horgan, & Sam Bauer, University of Minnesota

When given lemons make lemonade.  When given an ice sheet, conduct an ice melt study.  On January 31 at the Hancock Turfgrass Research Center (HTRC) at MSU we conducted an ice melting study in cooperation with Dr. Brian Horgan, Andrew Hollman, and Sam Bauer from the University of Minnesota.  We tested 20 products for their ability to melt ice.  Conditions during our treatment window which began at approximately 11 am and concluded at 5:30 pm had temperatures hovering around 25 °F and constant cloud cover.  The treatments can be broken down into three general categories:

Standard Chemcials/Salts (all application rates 28 lbs./1000 ft.²)

1. Calcium chloride

2. Sodium chloride

3. Potassium chloride

4. Magnesium chloride

‘Safer’ ice melt products (all application rates 28 lbs./1000 ft.²)

5. Calcium magnesium acetate (CMA)

6. Sodium acetate (NAAC)

7. Enviro Melt (carbonyl diamide/urea)

8. Safe Paws (modified amide/glycol admixture)

9. Paw Thaw (CMA and fertilizer)

10. Tenderfoot Ice Melter (urea and DeFrost)

11. Ammonium sulfate. 

Solar Absorption Products (dark colored)

12. Milorganite greens grade (56 lbs./1000 ft.²)

13. Sustane greens grade (40 lbs./1000 ft.²)

14. Top Cut biosolids SGN 90 (53 lbs./1000 ft.²)

15. Top Cut SGN 200 (53 lbs./1000 ft.²⁾

16. Top Cut + DeFrost SGN 200 (53 lbs./1000 ft.²)

17. BioDac + DeFrost SGN 200 (47 lbs./1000 ft.²)

18. BioDac + DeFrost + Colorant SGN200 (47 lbs./1000 ft.²)

19. Eon 75 humic acid (47 lbs./1000 ft.²)

20. Black sand (100 lbs./1000 ft.²)

Treatments on ice sheet at MSU.

We recorded surface ice temperatures prior to treatment application and at intervals following applications using an infrared temperature sensor.  We rated ice melt based on observation of standing water on the plots on a scale from 1-5 with 1 = no visible melt, and 5 = visible standing water. 

Surface temperatures prior to treatment application were very similar to air temperatures 25-26 °F.  One hour after treatment application the treatments were separated into two groups, the standard salts and safer ice melt products vs. the solar absorption products.  The solar absorption products with their dark coloration had surface ice temperatures of 35-37 °F whereas the salts and safer treatments had surface ice temperatures of 27-31 °F.  Treatments were still significantly different at 4.5 hours after treatment application although the temperatures for the solar absorption products declined to 30-32 °F, most likely due to the sun setting. 

There were also differences in visible melt from the treatments.  The following treatments produced the most visible melt: Milorganite, Sustane, Top Cut biosolids SGN 90, Eon 75 humic acid, and black sand.  The standard salts and safer ice melt treatments produced very little visible ice melt.  

Solar absorption products had the greatest melting.

The standard salts were the only treatments we observed that were able to penetrate through the 2 inch ice sheet so they could be effective in facilitating gas exchange with the surface but of course there is the risk of turf burning from the salt properties of these treatments.  

Calcium chloride melted holes all the way to the turf surface.

Overall, even though temperatures were below freezing and cloud cover persisted the solar absorption treatments were effective at melting the ice surface but were unable to melt to the surface given our 2 inch ice sheet. We are planning to replicate this trial again this coming week at both MSU and Minnesota when temperatures are forecast to be above freezing.  We will also be assessing turfgrass phytotoxicity from the treatments this spring. 

Helping the Melt

Next week most areas of Michigan are forecast to have temperatures above freezing and possibly into the mid 40’s in combination with rain.  Many superintendents have been attempting to clear greens down to the ice layer to facilitate melting.  Keep in mind that if this melt occurs there is going to be a tremendous amount of water that will be moving off greens.  Ensuring the water can exit the greens will be critical to try and prevent water backing up onto the green and refreezing if temperatures drop below freezing at night.  Ultimately Mother Nature is going to dictate whether or not our Poa annua putting greens have survived the ice sheet and the pending melting and freezing in the next month.    

What Lies Beneath: Ice?

Dr. Kevin W. Frank

Associate Professor & Extension Turfgrass Specialist

Michigan State University

Some might remember 'What Lies Beneath' as the title of a horror movie but currently ice is a real life potential horror for golf course superintendents worried about winterkill. 

Weather Scenario

The winter of 2013-2014 will be remembered for many years to come. The first significant event was the ice storm of Dec. 21-22 that knocked out power for thousands and coated everything, included exposed turf, with a perfect coating of ice. 

Tall fescue encased in ice.

Most turf areas were covered with snow prior to the icing event and as the rain percolated through the snow it formed a very porous, crusty ice-snow layer.  This type of ice-snow layer is not a concern for turfgrass as it is porous and allows for gas exchange from the turf/soil interface to the atmosphere.

  

Two inch porous snow-ice layer + 1 in. snow on top.

Five days after the ice storm (Dec. 27) temperatures at the Hancock Turfgrass Research Center (HTRC) warmed to 38 °F and were accompanied by 0.15 in. of rain. On Dec. 28 and 29 temperatures were above 40 °F.  The warm temperatures resulted in melting and I believe this is when the first ice layer formed.  On Dec. 30 temperatures dropped and we all learned what a Polar Vortex meant as day time high temperatures were in the single digits and nighttime lows were well below 0 °F.  The Vortex combined with a foot or more of snow closed MSU for Jan. 6 and 7 but by Friday Jan. 10 the HTRC recorded a daytime high temperature of 38 °F and by Jan. 13 the high temperature was 44 °F.  This resulted in another melting event and another ice forming event as temperatures in the day melted snow and nighttime temperatures refroze any remaining water.   Some superintendents that were clearing snow from putting greens throughout the winter may have been successful at removing any ice that existed or formed during these melts.  However, depending on available labor and equipment many superintendents are not able to constantly remove snow during the winter so ice formation is inevitable. Since the melting ended on Jan. 13-14 the temperatures have been well below the point where any further melting would occur.  Not every green at the HTRC is covered in ice but at least one poorly draining Poa annua putting green is now covered in a 1-2 inch ice sheet.  I believe this ice sheet initially formed during the Dec. 28-29 melt so as of today (Jan. 29) the Poa has been under ice for 31 days.   

Two inch ice sheet on Poa annua green at HTRC.

Ice Sheets

In Michigan especially for Poa annua greens, crown hydration and subsequent refreezing are often the primary culprits of winterkill. However, this year ice sheets are a cause for concern.  In the 1960’s James B Beard conducted research at MSU on survival of creeping bentgrass and Poa annua under ice sheets.  Creeping bentgrass survived 120 days of ice cover without significant injury while annual bluegrass was killed somewhere between 75 and 90 days of ice cover. More recently Darrell Tompkins conducted research at the Prairie Turfgrass Research Center in Canada that suggested Poa annua greens could be damaged in as few as 45 days under ice.  The primary cause of death to turfgrass under ice sheets is most likely from toxic gas accumulation under the ice sheet from soil and turfgrass respiration.  The day estimates for turf survival are just that, estimates, use them as a guide but know that they are not absolutes.

Remove Ice?

Whether or not to attempt ice removal is a difficult decision for golf course superintendents.  The decision to remove ice can be based on several factors including: turf sampling, duration of ice cover, current and future temperatures, ability to remove water following melting from the green, and labor.

1. Sampling – Bob Vavrek from the USGA recently posted a great YouTube video http://tinyurl.com/k9mbfjc on how to sample greens under ice to assess survival.  An important point that Bob makes is that there is variability in sampling and just because your sample comes out alive doesn’t mean all areas on the green will survive – same can be said if your sample is dead.   

2. Duration of ice cover – as discussed in the previous section, estimates of days of ice cover causing death vary from 45-90 for Poa annua and 120 days for creeping bentgrass.  At this point I’m less concerned for creeping bentgrass surfaces as I’d expect significant melting before we reach a 120 day threshold as this would be well into April.  Poa annua is less certain as at the HTRC we will approach 45 days under ice cover by mid-February.  Check your calendar and start counting. 

 

Ice sheet at HTRC, 31 days and counting.

3. Temperatures – our 10 day forecast does not look good for trying to remove ice as day time high temperatures are forecast in the teens to low 20's with nighttime lows in the single digits.  Part of the concern with removing ice is exposing the turf to cold air temperatures after being insulated with snow and ice since mid-December.  In the past, some superintendents have removed ice and then recovered the greens with snow to provide insulation against cold temperatures. 

4. Physical ice removal – physical ice removal includes practices to fracture the ice with impact (hammers, chisels, aerifiers, slicers) and then remove the fractured ice sheet with shovels, tractors, or skid steers.  I recommend avoiding direct impact with tools such as hammers to less impact concentrated equipment such as slicers and aerifiers.  There’s always some risk associated with impact related ice removal but the alternative of leaving ice in place and rolling the dice on survival is also risky. 

 

Damage from a hammer used to crack ice.

5. Melting ice – there are many different products that have been used to melt ice including black sand, dark colored natural organic fertilizers, and synthetic fertilizers.  The key to any melting strategy is to be able to remove the water from the green following melting so it doesn’t refreeze and form another ice sheet. We will be testing products to melt ice at the HTRC in cooperation with researchers from the Univ. of Minnesota in the coming weeks.     

6. Labor – if you’re going to remove ice you need help.  Ice removal is not a 1-person job. If your golf course has 18 greens covered in ice even with several employees this is not a one day job. 

No Guarantees

Unfortunately there are no guarantees with respect to winterkill and whether or not ice is removed.  The days under ice cover for survival are estimates from research and conditions from course to course and even within the same course vary thereby effecting how long turf can survive under ice.  It’s already been a long hard winter and let’s all hope our turf survives so it’s not a long hard spring reestablishing grass.