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Update (3/19/2013)

A Chilly Eve of Spring


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Weather


Late winter has been chilly in 2013, especially compared to a hot March 2012.

Although tomorrow is the first official day of spring, it’s hard to notice as the late winter of 2013 has indeed finally given us winter.  This is a polar opposite (thank you for the pun Pat Guinan) to 2012, which had a March with the highest recorded above average temperature in weather history.  From the latter half of February until now, we are running 5 – 9 degrees F below normal.  Soil temperatures are also well below normal, with average 2” temps hovering from just above freezing to the lower 40’s depending on location within the state. 

Mid February – Mid March 2013 also brought two winter storms (“Q” and “Rocky”) and much below average temperatures.  The two snowstorms, (with accompanying “thundersnow” which was interesting), caused the second snowiest February on record for both Columbia and Kansas City.  The resulting snow melt is a muddy March mess to go along with our March Madness. 

It is critical to not release mowers or other heavy equipment too early in these conditions; otherwise compaction and rutting of turfgrass areas will occur.  Hold on, spring will be here soon enough.  This is a good time, however, to start leveling and preparing seedbeds in those areas where the snow plows went awry, and escaped the roads or sidewalks.  Reseeding in necessary areas should probably wait another week or two, as these cool temperatures are forecasted to stick around for at least the next 10 days.  

Quick Hits


  • As expected, there is not a lot of disease activity that has been observed in the area yet.  We’ve done a couple of scouting runs around the turf farm since snowmelt, and haven’t noticed anything yet.  There was one unconfirmed report of mild snow mold damage on a lawn in Lee Summit, MO submitted last week, but a sample is unavailable for confirmation. 
With the abundant snowmelt moisture, large patch may be impactful throughout the region.
  •   Warning – Large Patch on Zoysiagrass & Bermudagrass:  With this excess of snowmelt moisture in the soil and thatch layer, I anticipate a large epidemic of large patch this spring.  If fungicides were applied preventively last fall, this will be a very challenging test for them.  Curative applications may be necessary this spring. I advise to close monitoring of areas with a history of the disease so you can catch symptoms quickly and limit disease damage.  When the large pathogen is actively infecting, the affected leaves will turn bright orange around patch margins.  Although normally more severe on zoysiagrass, I anticipate we may also see some large patch activity on bermudagrass this spring as well.    

Spring Dead Spot Research

Speaking of bermudagrass, I’d like to give a quick update on our research involving spring dead spot and again ring out a request for more samples.  In sports fields in particular, improved cold tolerant bermudagrass cultivars are being utilized more and more throughout Missouri.  The mantra has been that improved cold tolerance automatically yields a higher level of resistance to spring dead spot.  This has yet to be determined for a majority of these cultivars in Missouri, however, and we hope to acquire funding to establish plots and begin this research in 2013.

Spring dead spot research will be ongoing in 2013.

Our current research is steamrolling along.  We have three objectives to this research: 1) determine the spring dead spot species prevalent in Missouri and the surrounding region, 2) evaluate the impact of fertilizer, fungicide, and nitrification inhibitor on spring dead spot severity and 3) determine if nitrogen source or pH impacts the growth of the spring dead spot pathogen.  I’ll address each of these briefly below. 

  1. From 13 different sites (shown in figure above), we have identified through molecular analysis 71 out of 125 total isolates.  90% of these isolates (65 total) have been identified as Ophiosphaerella herpotricha, the most virulent species.  The remaining 6 isolates have been identified as O. korrae.  O. narmari has not been identified. 
  2. After the first year of field trials, only one treatment (ammonium sulfate + sulfur + two fall tebuconazole applications) resulted in a decrease in spring dead spot severity in 2012 compared to the initial rating date.  Only O. herpotricha has been found in this ‘Riviera’ plot, and these results demonstrate the difficulty in controlling this disease once established.
     
  3. In an agar plate-based assay, it does not appear that nitrogen source (ammonium vs. nitrate) impacts growth of either O. herpotricha or O. korrae enough to explain a potential suppression of disease in the field.  Neither pathogen grew at pH 3, but both species grew fairly well in pHs 5-9.  The assay is currently being conducted in liquid media to confirm this result. 

We’ve made good progress in this project, which is the emphasis of the M.S. thesis of Derek Cottrill.  We have one more year remaining, and are looking to make a final push in completing the research and acquiring more samples.  If you manage bermudagrass and have spring dead spot in Missouri or the surrounding region, please consider sending in a sample, or even better having us come out and sample at your site.  Either contact Derek Cottrill at djcnq6@mail.mizzou.edu or myself if interested in participating.

Happy Spring! 

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