SURVEY QUESTION

GOLF: Do you use a meter to assess volumetric water content on your greens?

Yes - daily
Yes - weekly
Yes - when needed
No

Update (06/08/2018)

Have a Slice

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Weather

May Swelter Continues in June

  1. June 4th was the first below average temp day since April 29! - Source: Missouri Climate Center
  2. Doesn't appear the summer heat is going to let up through mid June. - Source: NOAA

In case you missed it, May was the warmest on record not just for Missouri, but the warmest on record for the contiguous U.S. Eight states in total recorded their warmest temperatures in May including Arkansas, Illinois, Missouri, Ohio, Oklahoma, and Virginia. The first week of June hasn't afforded too much relief, although Monday was a bright spot as the first day with a below normal air temperature since April 29th. Despite this dip, June is already 4.8 degrees above normal in Columbia, 4.7 above in Springfield, 3.7 above in STL, and 3.5 above in KC. Forecasts do not indicate a cool down, as above normal temperatures are expected well into the middle of the month. Hope you enjoyed the 50 degree morning to start the week, because it doesn't look like we'll be feeling that again for a long time.

To close out May, subtropical storm Alberto did miss most of the region, walloping Indiana but only dropping a bit of rain on those in the eastern MO and western IL. This meant most of the eastern part of the region received nearly average rainfall for the month, while the middle and western part of the state had an inch or two deficit. The high temperatures and full sun conditions of May drove quite a deficit between short crop evapotranspiration (ET) and the amount of rainfall since May 1 (see below). Lawns and unirrigated areas are experiencing some drought stress, and soils that have developed water repellency (see story below) are showing their teeth.

Hot May Driving Water Away

  1. Since May 1, evapotranspiration has outpaced rain by almost 3 inches - Pat Guinan
  2. Unsettled conditions through next week give us rain chances. - Source: NOAA

Quick Hits

Brown Patch on Tall Fescue Strikes

  1. Early symptoms of brown patch in an 'RTF' tall fescue plot.
  2. Characteristic brown patch lesion on tall fescue - dark margin, tan interior.

  • Brown Patch on Tall Fescue - It's near impossible to top the amount of new disease activity in the last update, (and all of that still applies). Brown patch on tall fescue has been the new story in the last two weeks, igniting in a big way in late May and early June. Symptoms normally appear as three to four feet diameter patches that initially appear dark brown and watersoaked, particularly in the morning, but tend to dry into a light straw color. In the early morning dew, mycelium of the pathogen can be often observed. Individual leaf symptoms make this disease fairly easy to identify. Pick up a few leaves, and look for a characteristic lesion with a light tan interior and a dark, jagged margin. If this is on declining tall fescue, you've got brown patch.

    Leaf wetness (~ 9 hours sustained) is necessary to cause considerable damage, meaning lasting dew in early morning shade is the great meal ticket. Brown patch is therefore much more pervasive in shaded lawns but can also be driven by excessive irrigation as shown in the photo above. Cut back and control irrigation, and water in the early morning. Mow to the correct height – 3.5 – 4", and don't fertilize tall fescue now (preferably with anything) but especially not at high N rates or with quickly available N sources.

    Cultural practices are normally not enough to keep this disease at bay, and in many cases brown patch is the Achilles heel of tall fescue in the region. For those seeking a pristine, unblemished lawn a preventive fungicide program starting in mid-May is required. In prior trials, azoxystrobin (i.e. Heritage) applied 2-3 times on a 21-28 day schedule has been most effective in controlling the disease compared to propiconazole, myclobutanil, and thiophanate methyl, which are commonly found "over the counter" at retail hardware stores. Alternatively a homeowner can live with the damage and potential weed invasion over the summer, and invest that money in overseeding in the fall to rebuild density.

Have a Slice

As noted above, spring is a season for another year, with May ET rates high and precipitation not keeping up. In these summer times when heat reigns and rain from the heavens can't keep up, the yin of too much water and the yang of too little water on golf greens often leads to trouble. In the last two weeks, we have observed both in samples submitted to the lab and also on our research areas. These problems are quite apparent if you do what we do first in the diagnostic lab… lop a slice out of the soil profile pie.

Water issues are often quite apparent if the right equipment and methods are utilized. Obviously TDRs for assessing soil volumetric water content are the cutting edge, but taking a soil sample and being familiar with your soil profile is still a necessary aspect of greenkeeping. Sand falling out of the bottom of the pulled core is an obvious sign of water repellency and low soil moisture status. A normal cup cutter plug can and should be simply cut in half to reveal the soil profile. This flat surface can reveal OM layering and black layer or provide a platform to conduct water repellency testing. A rectangular soil profiler is also a perfect tool to provide this surface. Leaning on a ¾ or inch soil corer to get down to the pea gravel layer may yield even more insight into why water may not be moving like it should through a putting green soil. Below is information on how to detect and deal with this yin and yang of abiotic issues regarding water by sampling struggling areas. Before shipping a sample off to a diagnostic lab, you might as well have a good look yourself.

Split the Plug Open to Find Black Layer

  1. Looking at the profile can reveal OM layering and resultant black layer formation.
  2. Black layer can even form on the roots themselves, creating a toxic situation.

Black Layer – Black layer is formed when soil conditions are anaerobic, benefiting bacteria suited to the oxygen depraved environment that also unfortunately produce sulfurous toxic byproducts and cause root decline. Bentgrass roots also don't grow and prosper without oxygen, creating a double whammy situation. A lack of water movement and infiltration is the major cause of black layer, as stagnant water replaces air in soil pores. Black layer can form just about anywhere in the profile, so vigilance is necessary. If decline occurs, particularly in low areas of the green, take a deep sample with a ¾ inch soil corer, and lean on it to get down to the pea gravel. Inspect the soil and look for distinct color changes throughout the profile and even use your nose to detect the distinct sulfury "smell of death" that may emanate. Also look for rust or gray colored patches which may indicate a case of iron cementing. You may also use a rectangular soil profile or split cup cutter plug to look for layering and how pervasive the black layer is in the top 4-6 inches.

If black layer is detected, aerification is necessary, especially if organic matter layering or excessive accumulation is the cause. During the summer, solid tining may be the only recourse, but keep the hole open as long as possible. If core aerifying, fill the holes up with fresh sand. Last but most importantly, check the drainage below as black layer is a sign that hydraulic conductivity is poor and excessive OM might not be the only cause. Has the plastic 4-inch collapsed or is choked by tree roots? Is a liner the problem? Does a smile drain need to be installed? Iron cementing or other soil issues?

Localized Dry Spot Showing with Increased ET

  1. LDS has grown quite severe on our native soil creeping bent fairway research area.
  2. Test at different depths of the core, since hydrophobicity can develop below the top inch.

Localized Dry Spot – Rightly so, turf managers are instructed by pathologists that too much water kills. Keeping greens firm, fast, and dry is a tenet that benefits green speed and game play, and too much water results in too little air in pore spaces and a beneficial environment for soilborne pathogens. When the current high ET bus is careening down the road and the soils turn hydrophobic however, a true water deficit wilt can happen quickly and cause considerable damage. Water repellent, or hydrophobic soils are most often caused by the organic acid byproduct of organic matter degradation by soil microbes. These organic acids strongly adhere to soil particles, particularly sand, and are hydrophobic. These hydrophobic soils, or localized dry spots (LDS) repel water away laterally and cause preferential water flow, limiting or eliminating water to roots below. Water repellency can occur on most any soil type, as seen above on our native soil creeping bent fairway trial.

TDR meters have allowed for much more rapid and accurate detection but won't definitively reveal a case of LDS. Instead rely on a very simple test that uses the old school rubber balled eye dropper. Get a flat surface, either with a soil profiler or by cutting a cup cutter plug in half, and with the eye dropper place droplets at various depths and areas of the profile. If the droplet doesn't seep in by 10-30 seconds a hydrophobic condition is occurring. In most cases on sand-based putting greens that water droplet will sit there for quite a while (I've seen + 3 days) before seeping in or even just evaporating. Remember to place droplets at various depths, as in some cases repellency will develop at a two to four inch soil depth and act as a non-draining pot to keep the water near the surface. While difficult to explain, some samples may have cyanobacteria on the leaves and along the soil surface but extreme hydrophobicity a few inches below. This pot with no holes effect and constant hand watering is most likely the cause.

Like with black layer but for a completely different reason, punching holes into a hydrophobic soil profile is crucial to get water back into areas and break up preferential flow. A soil surfactant, perhaps tank-mixed with a fairy ring targeting fungicide, may also provide relief for extreme LDS symptoms. Unfortunately, just watering these areas more is not the solution since these hydrophobic coatings strictly adhere to soil particles and can't just be washed away.


Lee

Lee Miller
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Extension Turfgrass Pathologist
University of Missouri