SURVEY QUESTION

GOLF: What fungicide do you rely on to target Pythium root diseases on putting greens?

Subdue
Insignia
Heritage
Segway
Banol
Signature
Phosphite
Rotate Evenly
None of the above

Update (06/19/2014)


Diseases a Plenty

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Weather

A strong summer dose of warmth and humidity greets us before the summer solstice.

We are just a little over a day away from the summer solstice (a cause for party for some), and the environment is definitely ramping up.  We are experiencing our highest low temperatures of the year (in the mid 70s), very high humidity (ranging from 62 -85% yesterday at the farm), along with considerable wind and high ET rates (0.31 inches yesterday).  To go along with the spike, most areas are well above normal for the amount of precipitation received thus far in June (1” – 2”+).  If you’re a soccer fan, it feels like the relentless pressure Ghana put on the U.S. defense through much of the game Monday evening.  As you can see below, there have been several cool-season turfgrass issues (pulled hamstrings and broken noses) that have occurred in the last two weeks.      

After speaking with our resident state climatologist, Pat Guinan (who you can meet at the field day on 7/22), the forecast over the next few days and into next week is a bit tricky.  A front is dumping considerable precipitation (and some tornadoes) north of us, and is forecasted to slip down over Missouri.  How far it slips, and how long is stays, is a determinant of how much precipitation falls and how far down temperatures will dip throughout the region.  Northern Missouri and Kansas City (which doesn’t need it) may stand to get most of the rain during the period.  The decline in temperatures forecasted next week will help, but if lows stay in the mid - upper 60’s there will still be ample opportunity for continued disease pressure.  

Weather forecast shows above normal chance of precipitation and a cool down for next week.

Quick Hits (a plenty):  

Pythium blight and leaf spot occurring on Kentucky bluegrass sports turf.
  • Pythium Blight/Leaf Spot Issues on Sports Turf:  A combination of  Pythium blight and Drechslera leaf spot was observed infecting several Kentucky bluegrass and Kentucky bluegrass/tall fescue sports fields in Columbia.  These fields had a late spring N application on them and no preventive fungicide application, and the saturated conditions made them prime for attack.  The Pythium was the main driver of the damage in this case, with the scattered leaf spot causing fungi in tow.  In these current conditions, we often observe these disease complexes where diseases like Pythium blight, Rhizoctonia brown patch, and leaf spots can all be found and are actively damaging susceptible areas.  This is especially true in shaded, wet tall fescue, where both Pythium and brown patch can be acting together to cause damage.   In the above-mentioned case, the field manager applied a targeted Pythium fungicide (Banol) and a DMI to halt further development of both diseases.
    Pythium root rot should still be active in the region.
    • Pythium Root Rot on Putting Greens:  If we’re inoculating, it means it might be time to be preventing.  On the day of the last report, we (the team of Daniel Earlywine, Max Gilley, and student workers Matt Malinski and Kyle Robertson) inoculated a fungicide evaluation trial in the hopes of spurring Pythium root rot.  Since the last report, we have received only one sample with substantial oospore amounts in roots (which also had a population of root knot nemas), but that doesn’t mean this disease isn’t working down below.  In the last report, I posed the question of which fungicide superintendents rely on for Pythium root disease control.  Even with the low sample (21 responses) the results are interesting and posted above.  The survey is left up again for this update, so if you manage golf greens, please weigh in… 
Cyanobacteria (blue green algae0 causing issues during wet conditions in mid June.
  • Cyanobacteria/Blue Green Algae: The wet conditions have led to a considerable amount of blue green algae (or cyanobacteria) invasion on golf putting greens.  Two samples within the last week have come into the clinic with appreciable levels of Nostoc (appearing as black balls within the turfgrass canopy) and presumably Phormodium (shown above).  Cyanobacteria can compete with other organisms by producing toxins, excreting siderophores to compete for iron, or clogging soil macropores and creating a black layer condition.   They have also been implicated as the cause of a disease known as yellow spot, which involves a distinct chlorosis presumably resulting from the toxin.  Cultural practices to reduce this problem rely on drying down the turf surface and mat layer.  At this time of the year, vent tining may greatly aid in this process along with careful irrigation.  Regular applications of chlorothalonil and mancozeb may aid in algae reduction. QoI fungicides (Heritage, Insignia, Compass, etc) may result in higher levels of yellow spot, so a regular application schedule of chlorothalonil may be necessary to maintain adequate algae levels when QoIs are applied.  For a more complete summary and explanation of cyanobacteria effects on putting greens, click here to read a great research article written by Tredway, Stowell, and Gelernter.
     
  • Brown Patch Still Raging:  As noted in the last update, brown patch on tall fescue and creeping bentgrass is raging across the turf farm.  The conditions have been perfect for this disease, and if they continue it will be a banner year for this disease.  See the last report for more information on managing this disease.

  • Dollar Spot Still Spotting:  Dollar spot on creeping bentgrass and Kentucky bluegrass is also still chugging along and causing considerable damage at the turf farm. 

    Anthracnose starting to go into basal rot mode on susceptible bentgrasses.
  • Anthracnose:    Not to be left out of the fun, the beginnings of basal rot anthracnose infection were noted in a putting green sample from central MO.  While there were quite a few pathogens in this sample, (including the Pythium root infection noted above and the root knot population noted below) the anthracnose was noticeable enough to be worrisome.  Researchers at Rutgers University have been working on this disease for several years now and have published a great white paper detailing the best management practices they have elucidated through their research.  Click here to read the management summary.  While this is suited towards annual bluegrass putting green maintenance, many of the same tenets should hold true for susceptible creeping bentgrass cultivars such as Penncross, Pennlinks, Providence, SR1020, and Dominant.  Fungicides are best used preventively on areas with a history of the disease, and utilization of as many different fungicide chemistries as possible during the season will maximize control and potentially reduce fungicide resistance issues.  Be careful with DMIs during the heat of the summer though…

  • Root knot nematodes were also found in the above sample at 120 nematodes/100 cc of soil.  This is just above the action threshold of 80 nematodes/100 cc of soil utilized by many university labs.  In previous observations of pronounced damage from root knot nematodes in STL, the samples had thousands of root knot nematode juveniles per 100 cc of soil and the galling on roots was significant.  In this case, the superintendent caught the problem early and is taking action to prevent further population increase.  

    DMI phytotoxicity noted on a green with repeated high rate applications.

  • DMI Phytotoxicity on Putting Greens:  I’ve broached this subject before, and the phenomenon is fairly well known.   With the increased heat over the past week, we’ve noticed over the last week some plots standing out that were sprayed with DMIs on a short interval.  Just to serve as a reminder the DMI chemistry, [i.e. propiconazole (Banner), triadimefon (Bayleton), and metconazole (Tourney)] should be left on the shelf during periods of heat stress on bentgrass putting greens.  Briskway, a tank-mix of difenconazole (DMI) and azoystrobin, is the one exception to this rule as in our studies even doubling rates didn’t produce this phytotoxic density loss and bronzing effect.        

Field Day, July 22nd – Save the Date.

Plans are underway and the full agenda is nearly set for the 2014 Mizzou Turfgrass & Ornamental Field Day.  The event will be held July 22nd at our research facility at South Farms.  Slated speakers will include Pat Guinan, state climatologist, Patricia Wallace, Director of the MU Plant Diagnostic Clinic, Dr. Hank Stelzer, Dr. Xi Xiong, Dr. Brad Fresenburg, myself and others. Registration is now open for vendors and attendees! 

Attendees click here to register.

Vendors click here to register.

Hope to see you at field day, 

Lee

Lee Miller
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Extension Turfgrass Pathologist
University of Missouri