Michigan State University
The winter of 2013-2014 shattered weather records and Poa
annua putting greens. Ice cover that
endured from early January through mid-March was a significant factor in
causing winterkill but there were certainly situations where crown hydration
freeze injury or even desiccation injury on exposed sites also caused
damage. With winter on the horizon there
is plenty of discussion on what to do now and what to do during winter to
minimize the risk of winterkill.
Shade
Following last winter it was clear that any turf that was
weak or simply not as healthy was exposed and killed. In many instances the winterkill patterns
mirrored shade patterns on greens.
Turfgrass growing in the shade is simply not as healthy as turfgrass
growing in full sunlight. To compound
the problem trying to reestablish damaged greens in the shade resulted in
longer recovery time than greens recovering in full sunlight. Improving sunlight penetration to greens by removing
and/or thinning tree canopies will improve turfgrass health and ultimately may
improve the odds of turfgrass surviving winterkill events.
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| In some instances winterkill mirrors shade patterns. |
Covers
Covers are not widely used throughout Michigan, especially
southeast Michigan. There are probably
several reasons including cost, storage, lifespan, and unpredictable winter
weather. Last winter was extreme with
ice, snow, and cold temperatures. The
winter of 2012 if it’s remembered at all, is remembered for the mild
temperatures that resulted in golf being played almost all winter long. Keep in mind that all covers are not the
same. The permeable covers that were
purchased by many golf courses this spring provided a tremendous advantage in
reestablishment but will not provide absolute protection in the winter from thick
ice cover. Permeable covers will
certainly provide some buffer/protection from low temperatures and desiccation and
should be used if available but if this winter delivers another dose of lengthy
ice cover, permeable covers can’t be counted on to prevent damage.
Impermeable covers will protect the turf from ice cover
damage but are not necessarily a panacea for all your winter worries. Impermeable covers need to be ‘tucked down’
tightly to the surface to prevent any water from getting under the cover. Impermeable covers will prevent gas exchange
with the atmosphere so in that respect they actually mirror thick ice
sheets. Venting (exchanging air under
the cover) impermeable covers throughout winter reduces the risk of anoxia
developing under the cover. To use or
not use covers, especially impermeable covers can be a hotly debated
topic. Ultimately the golf course
superintendent is the person that should make the decision. After all no person knows the golf course,
the environment, and the turf better.
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| Covers can be used for winter protection and reestablishment. |
Snow Mold &
Covers
It is important to remember that greens covers act similar
to snow cover when it comes to snow mold activity. The covers provide the same
environmental conditions for the development of snow mold as the snow does. So
if greens covers are placed on the greens in November and not removed until
March, they will create the same environmental conditions for the development
snow mold as golf courses in Northern Michigan experience where snow covers the
turf for three or more months. It is
important that adequate levels of snow mold fungicides be applied to protect
the turf for three or more months if covers will be used for this length of
time. This usually means applying 3 way fungicide combinations at full label
rates. Microdochium patch will occur throughout the fall. It is most
active when the temperatures are in the 60’s and combined with wet weather.
Therefore, it is important to make fungicide applications throughout the fall
to prevent Microdochium patch from
developing. If Microdochium
patch is active at the time the covers are placed on the greens, it will
continue to develop under the covers in spite of any fungicide
applications.
Winter Snow & Ice
Removal: To Remove or not to Remove?
This question might make the cover debate seem tame. Should you remove snow and ice and if so when
should you start? Last year was an
anomaly with thick ice sheets that were in place for 90 days or greater in many
areas. Although some courses have been
successful with removing snow throughout the winter this may not be feasible
for some courses due to either lack of personnel or snow moving equipment. Instead of being concerned with removing snow
from the first event to the last, consider developing a removal strategy that
targets ice duration and snowmelt that could lead to crown hydration freeze injury. For example, if ice forms and is in place for
greater than 30 days I would definitely make attempts to remove. For crown hydration freeze injury consider
removing snow in late February/early March prior to anticipated snowmelt.
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| Removing snow from a putting green. |
Surface Drainage
The key to preventing or reducing the incidence of crown hydration
freeze injury is good drainage. For
putting greens that lack adequate surface drainage, consideration may even be
given to recontouring greens that are annual victims of crown hydration
injury. Less dramatic measures include
cutting cup cutter sized holes in poorly draining areas and filling the cores
with gravel or sand to try and move the water away from the surface. Another more common tactic is to cut sod
strips from greens to facilitate water movement off the greens once snowmelt
begins.
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| Help the melt by stripping sod (photo courtesy Adam Garr) |
Cultural Practices - Let
it Grow!
Fall is prime time for cultural practices to improve
turfgrass health. In addition to core
aeration and fall fertilization consideration should be given to raise mowing
heights as fall progresses. Higher
mowing heights won’t save the turf alone if winterkill is again an issue, but
it could certainly be a factor in producing a healthier plant and if you think
back, how many putting greens had winterkill but the collar had no damage? Granted, the greens aren’t going to look like
collars going into winter but maybe even a slight increase in height might help.
