GOLF: If you use a TDR sensor to measure volumetric water content, what is your target range on putting greens?


Update (7/25/2013)

More P = More Poa

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Mizzou Field Day next Tuesday, July 30th at 8:30 am

Field day talks include wetting agents, tree care, lawn care, and disease updates.

Make plans to join us next Tuesday for the University of Missouri Turfgrass & Ornamental Field Day held at South Farms (directions can be found here).  We have a great lineup of topics and speakers during our morning sessions, and have three informative afternoon tours given by local experts that follow a golf, sports turf, or landscape/horticulture track.  In addition, we have 15 vendors lined up and ready to show off equipment and plant management solutions.  It’s a full day celebration of learning and camaraderie.  Plus, the temperatures couldn’t be better for a MO July.     

Links are below to access registration for both attendees and vendors, and the complete field day agenda. Hope to see you there. 

For the full agenda, click here.
For attendee registration, click here.
For exhibitor/vendor registration, click here.


July has been average temperature-wise and dry.

In the words of our state climatologist, “What a difference a year makes!”.  Last year, July was the 5th hottest on record, which makes our current average July feel like a cold blast.  The remaining July forecast also looks like a string of pearls, as the jet stream will push a cold front through \ Missouri and leave some areas only having weekend highs reaching the 70’s (can that be right??). 

Precipitation thus far in July has been spotty, with some areas like Jefferson City right on the monthly average, but most others running from 1.5” to even 3” below normal for the month.  This dry July pattern has put us on the radar of the US drought monitor (, but as I noted last week not nearly at the severe level like last year or currently in western KS.   The currently passing cold front is giving Kansas a dose of rain now and should impact Missouri this Friday and early weekend, so hopefully some tall fescue lawns will pop out of dormancy.

Quick Hits

  • Heat/drought stress on tall fescue lawns has been an issue over the last two weeks.  With the (now previous) heat stress and lack of water, these lawns will not take traffic very well.  In particular, it is important to restrict mowing on dormant or heat stressed lawns.  In several lawns around the area, I’ve noticed lines of discolored mower wheel tracks where lawns where mowed during the heat of the day.  If it’s browned out or looks wilted, water it or let it be…
Putting green root systems are showing signs of decline.
  • Too wet:  On putting greens, physiological root decline has been prevalent on samples as we enter into the last chapter of summer.  Our wet spring has set up some greens with high organic matter content by creating a waterlogged, low oxygen condition at the exact time bentgrass root growth is needed most.  This root decline is observed as darkened vascular cylinders, and sloughed off epidermis and cortex layers.  As you can imagine, numerous secondary pathogens swarm in on the compromised tissues, including take all patch and Pythium spp.   Many superintendents are using penetrant type wetting agents to get this water through the profile, past the organic matter, and out of the top inch.  In addition, routine venting of greens with solid, pencil or bayonet tines should be done to promote water infiltration and get the bad air out. 
Localized dry spot and some fairy ring impacting greens.
  • Too dry: On the flip side of this, there are also several superintendents dealing with localized dry spot (LDS) and some fairy ring activity as we go through this brief period of drought.  In one case earlier in the month, the LDS had set in an inch below the surface below the organic matter layer.  At this point, a wetting agent should be used to combat LDS, and if fairy ring is the problem, a fungicide (ProStar, Heritage, or Insignia) should be tank-mixed with a wetting agent.  Again, venting is also suggested in these areas.   
  • So how to get soil moisture just right?  I would be remiss not to mention the utility of TDRs or time domain reflectometer sensors.  These devices are gaining popularity among many superintendents for measuring volumetric water content and dialing in soil moisture on putting greens.  If you are using one, what’s your desired range?  (See survey above). 
Algae infestation on putting green turf.


  • I am also noticing considerable amounts of surface and foliar algae on recent putting green samples, particularly from those that also have wet soil profiles due to over-irrigation or high organic matter.   Many pathologists may not consider algae a true pathogen, but where there is a canopy opening it is obvious that algae competition considerably reduces the ability of the bentgrass plant to regrow.  Some of these algae (aka cyanobacteria) have been shown to produce a phytotoxic secondary metabolite to gain this competitive advantage, and can cause a disease termed yellow spot in otherwise healthy bentgrass.  Daconil Ultrex, mancozeb, and the phosphite fungicides have been shown to restrict algae growth and allow for bentgrass regrowth.  In addition, switching to an ammonium sulfate nitrogen source and using a wetting agent may also help reduce algae infestation.  For more information from some of my colleagues on this subject, several links are provided below.

Don't put P on the Poa

Increasing levels of phosphorous may encourage Poa annua infestations on greens.

As some of you know, I left the country last week for the International Turfgrass Research Conference (ITRC) in Beijing, China.  I call the ITRC the Olympics of turfgrass because it occurs every 4 years and brings together a diverse variety of turf researchers that may not interact on a regular basis.  Despite its tough time on the schedule for an extension turfgrass pathologist, discussions of water and pest management issues with colleagues from Australia, China, Great Britain, etc, are invaluable benefits to attending this conference. It also was my first time in Asia, (for all 72 hours of it). The cultural experience was extraordinary, and I learned quite a bit about life on the other side of the world. 

A piece of research that caught my attention at the conference was authored by Raley, Landschoot, and Brosnan (from Penn State and UT) and investigated fertility practices and their impact on Poa annua infestation of a 2-year old bentgrass putting green. In this 2-year study, nitrogen rate had no impact on the amount of Poa annua infestation.  The rate of phosphorous, however, did have a pronounced impact on Poa.  P treatments included ~ 1, 2, or 3 lbs P/1000 ft2 per year in 5 equal applications, or no P treatment.  All treatments that included phosphorous had increases of 3-7% Poa cover (no difference among the three rates) whereas Poa cover actually decreased (2%) in plots that were not treated with phosphorous.  In addition, turfgrass color ratings were higher in plots that didn’t receive P, because there was less Poa infestation.  This correlation isn’t the first time higher Poa infestation was linked to exogenous P application, but it definitely drove the point home.             
Hope to see you next week at Field Day!

Lee Miller
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Extension Turfgrass Pathologist
University of Missouri