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Update (9/26/2012)

Already a Rhiz-"Octoberfest"

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Average temperatures for the region in September.

September weather may turn out to be just about average, which is a far cry and welcome relief from the previous 11 months of unprecedented warmth.  In fact, I’m not so sure I’ve ever been so happy to see a “70% C grade” after all of the “F” weather of this past summer.  This break, accompanied by frequent rainfall to recharge a seriously depleted soil water condition, has brought many turfgrass lawns and landscapes back from the predicted point of extinction.  It is truly amazing how drought tolerant some species are, (particularly tall fescue), when you reflect on the putrid status of unwatered lawns just a few weeks ago.  This resiliency has eased some of the burden that many thought was going to come from extensive turf renovation projects.

Soil temperatures (2” bare soil) have steadily hovered around 70°F for the last 14 days throughout the region.  Along with reduced photoperiod length, this is cause for cool season grasses to put on weight for the winter season, and for warm season turfgrasses to start going softly into that good night.  This decline in growth of the warm seasons, particularly zoysiagrass, increases susceptibility to opportunistic turf diseases (as noted below and in the last update).    

Soil temperatures are hovering around 70F for most of the region.

The Rhizoctonia Show

Fall temperature Rhizoctonia disease outbreak on creeping bentgrass putting green

After the consistent rainfall of the last 14 days, we noticed a weird orange  double ring, accompanied by a smoke ring of mycelium on our creeping bentgrass research plot at the farm. This was noted briefly in the last update, but our farm observation was accompanied by a report of similar symptoms on a course in Branson, MO.  We noted Rhizoctonia-like mycelium in the sample, have isolated it, and are in the process of identifying it with molecular tools. There was a common link between the two sites on the use of Tourney as a sole fungicide in the last 14 days, but this may be mere coincidence. After application of a Rhizoctonia specific fungicide like ProStar or Heritage, Affirm, or 26GT + chlorothalonil turfgrass quickly recovers.  However, this goes to show that Rhizoctonia on creeping bentgrass may not just be for brown patch and the heat of summer any more.     

Large Patch on Zoysiagrass

Large patch outbreaks are flaring up considerably around the region.

Adding to the Rhizoctonia theme, with the recent rains and conducive fall soil temperatures (see above), large patch is firing on all cylinders now throughout the region.  Earlier less noticeable infections have blown up to epidemic size proportions in some areas, particularly those in low spots or that don’t drain well. Increasing drainage is a good way of minimizing large patch infection, as saturated soils in low spots tend to get the worst disease outbreaks.  In addition, as I noted in the last update, do not aerify or fertilze zoysia now as this will predispose zoysiagrass to violent large patch infections.     

It is recommended in areas that have had problems in the past, that a preventive fungicide be applied now (if not earlier).  This is especially true for homeowner lawns in the St. Louis region that have incurred the wrath of this disease over the last two spring seasons.  Preventive applications of Heritage, Headway, Triton, ProStar, Pillar or Torque should be made once ort twice in the fall with the second being 21-28 days later.  Granular formulations of some of these products include Heritage G, Headway G, and Pillar G.  Early testing results indicate these granular formulations are just as effective as their sprayable counterparts if applied correctly.  The key point is that these granulars must have water to be released from their solid carrier, so irrigating afterwards (if rain doesn’t occur) is necessary for activation.  It’s also important to note that even if fall preventive applications are made, a curative spot application may be necessary in the spring f high rainfall occurs. 

As an added footnote, I wanted to point out and thank the super senior from our MU turfgrass science program who took the photo above. The young man's name is Jacob Rockhold, and he is fresh back from an internship along with his MU cohort Erik Meyer at Baltusrol Golf Club in New Jersey. We heard nothing but good reports on the two, and we are proud that we could place them in such a rewarding intership program. Jacob is currently working on large patch as the subject of an undergraduate research project in my lab, and is slated to graduate this December. If I can't lure him into the dark side of investigating the science of turfgrass pathology, I'm sure he will become a fine leader on any golf course maintenance staff.

Go Tigers!   

Lee Miller
Follow on Twitter!  @muturfpath
Extension Turfgrass Pathologist
University of Missouri