University of Arkansas, Division of
Agriculture, Cooperative Extension Service
Turfgrass Science Program (http://turf.uark.edu) – Turf Tips
It
seems like only yesterday that we were sending out Turf Tips to our local
industry about the potential for winterkill on warm-season turfgrasses and what
to do about it. The truth is we had one of the more severe winters of the last
10 years and many golf courses, athletic fields, and other turf sites around
the state and region had to deal with winter injury on their warm-season
turfgrasses. In our research plots at Fayetteville, we saw significant winter injury
on St. Augustinegrass, Seashore paspalum, bermudagrass, and even zoysiagrass (a
first for me).
I
am not sure why I thought this, but the law of averages would suggest that a
really bad winter should be followed by a nice, mild summer that lets everyone
get caught up and recover from the problems of winter. Right? Unfortunately, we
have followed a bad winter with one of the most difficult stretches of hot,
humid weather that Arkansas and much of the United States has seen in the past
decade or longer.
With
the proliferation of social networking, blogs, and news media, it is easier
than ever before to keep up with what is going on in the turf industry or any
other aspect of society. One of my favorite blog sites out there is the turf
disease blog site (http://turfdiseases.blogspot.com/), where some of the nation’s best turfgrass
pathologists update their readers on the kinds of problems they are seeing in
their region, especially as samples pour into their plant disease diagnostic
labs. As I was visiting the site the other day, I was struck by the titles of
the five most recent blogs posted on the site by these prominent turf
researchers:
·
Poa annua takes a dump – Jim Kerns, Wisconsin
·
Heat + Rain =
Dead Grass – Brandon Horvath, Tennessee
·
No wind = Dead
grass – Lane Tredway, NC State
·
Heat wreaking
havoc on golf courses nationwide – John Kaminski, Penn State, and Clark
Throssell, Director of Research, Golf Course Superintendents Association of
America
·
Relentless heat
and humidity – Megan Kennelly, Kansas State
You
really don’t even have to read the articles to know that things are tough all
over. However, if you want a sense of what is going on around the nation, I
suggest you read all these articles, especially the one by Kaminski and
Throssell. In one of the articles, there was a discussion on this year’s
weather compared to the past, so I started digging around in some of the
weather archives to see where we are in Fayetteville, Arkansas relative to
year’s past. Probably the most telling data is the number of days where we have
experienced extreme temperatures. If you look at the 30-year average, July will
normally have 13 days where the mercury rises above 90 °F. July 2010 in
Fayetteville had 20 days where the temperatures went above 90. Normally, this
would not be a huge problem, but this above-average July is following a June
where we had 13 days above 90 compared to an average of 5 days over the last 30
years. The really bad news is that August is typically the hottest month of the
year, so we are nowhere near out of the woods.
In
addition to the excessive temperatures that we have been experiencing, we are
also in a cycle of very high humidity, thunderstorms that add to the humidity
and heat load, and minimal wind. All these factors create an environment that
is almost impossible to keep bentgrass and other cool-season grasses going
strong. If we go back to plant physiology 101, it is pretty clear how these
extreme high temperatures might affect creeping bentgrass greens. Bentgrass has
an optimum temperature for photosynthesis between 55 and 75 °F. When we exceed
the 90° threshold, the ability of bentgrass to produce energy from
photosynthesis drops dramatically. In addition, high temperatures cause respiration
rates to increase, which means the plant is burning more fuel than normal. So,
in total, we have a system that has reduced energy intake and increased energy
consumption and that can only be sustained for short periods of time, not the
duration we are currently seeing. A good analogy would be trying to reduce your
food intake by 80% while running a marathon – within a short period, your
energy reserves are going to be depleted and you will stop running.
The
high humidity and limited wind is also an ideal environment for diseases to
thrive and pathogens are attacking weakened plants at an alarming rate. One of
our key research projects at the UofA is to screen grasses for adaptation to
our environment and getting a lot of disease pressure is really good for our
research. However, in my 13 summers at the UofA, I have never seen disease as
severe as what we are seeing right now. I have over an acre of various tall
fescue cultivars that has been almost completely wiped out by Rhizoctonia brown patch (see picture below). It is so bad that many Kentucky bluegrasses
are getting brown patch, which is a rarity and I have never seen at Arkansas.
I
have already had to visit a number of golf courses this summer that are
struggling to keep greens alive and I really don’t have an easy answer on how
to do it. Once the turf starts on a downhill spiral, it will not be able to
fully recover until environmental conditions improve. Preventative fungicides,
good fertility, proper mowing, fans, good irrigation practices, etc., are all
critical as you move forward, but these are only band-aids that will keep the
wound from gushing blood until cooler temperatures return. It is also
critical for golf course owners and managers to understand that really bad
weather, like cancer, does not discriminate based on wealth or social status,
so golf courses with both unlimited budgets and shoe-string budgets will feel
the consequences of the weather we are experiencing. Management and players
need to have realistic expectations during stressful periods like this and not
get too excited about a few weak spots on the greens.
In
Kaminski and Throssell’s article on the turf disease blog, they listed the
following recommendations for dealing with these conditions and they are good
recommendations for Arkansas as well:
·
Raising the
mowing heights of playing areas, most notably putting greens.
·
Alternating daily
practices of mowing and rolling putting greens, with consideration to skipping
a day if the schedule of play allows.
·
Forgoing double
mowing, topdressing, verticutting or grooming greens.
·
Watering to
provide adequate soil moisture, but not over watering as saturated soil will
cause the turfgrass to decline rapidly.
·
Hand watering as
much as feasible. If a green has a dry spot or two, superintendents will hand
water the dry spots only and will not water the entire green. When the entire
green shows stress from a lack of water, superintendents use the overhead
sprinklers and water the entire green.
·
Avoid aerifying
using large diameter tines that penetrate deeply into soil and remove a core of
soil. If a superintendent feels the putting surface is sealed, venting using
small diameter solid tines or other similar technique is employed.
·
If fertilizer is
required, small amounts of fertilizer are applied via a sprayer and observation
of the response occurs before fertilizing again.
·
Monitoring and
adjusting golf car traffic patterns to minimize stress to turf.
The
one strategy they failed to mention was prayer for a change in these weather
patterns – football season cannot get here soon enough!! Hang in there and let
us know how we can help.
Mike Richardson, Professor
University of Arkansas
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