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Update (6/5/2012)

The Burning Ring of Spring

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Record warmth in spring 2012 for Missouri

Well, in case you didn’t notice, it’s been warm.  Really warm.  Maybe more accurately downright hot.  This past spring (March – May) has been one for the record books, officially being the hottest spring on record in 115 years of weather recording.  And #2, 1977, wasn’t even close.  Let’s recap:  March was 14°F (!!!!) above normal and the hottest March ever.  April was a mere 4°F above normal, and May was nearly 7°F above normal.  To put this into even more perspective, the preceding 12 months from June 1 – June 1 have been the warmest ever.  Every single month except September (3°F cooler) was above the 30 year normal, including the last 8 months in a row.  This span of 8 months with above normal temperatures did occur in 2010, but this span ranged from 0.3 – 5.3°F above with an average of ~ 2.4°F.  This past 8 months ranged from 2.1 - 15°F above normal with an average of ~ 5.9°F. 

So what does this mean for turfgrass health?  Everything will be coming early this year.  In the Quick Hits section below, there are several pests that are normally scheduled for July 4th fireworks that are occurring now.  Considering these warm temperatures, turf diseases have been relatively quiet, particularly in mid Missouri, because…

Low precipitation throughout Missouri in May has led to drought conditions.

May was an extremely dry month for Missouri.  Using Columbia as a barometer, (which is ridiculous considering the variation that occurs in the state), May should be our wettest month with 4.98” of precipitation on average.  The total May rainfall total recorded at the airport this past May was 1.2”, which is high considering at the turf farm and at my house we only recorded ~ 0.4”.  Evapotranspiration loss during the spring, driven by the high temperatures, unrestricted sunlight, and moderate winds, mirrored those in summer with monthly rates in the 4-5” loss range.  Combined with the inadequate May rainfall, these conditions have led to drought conditions in turf, gardens, field crops, and even deep rooted mature trees!

Our overall yearly total is actually higher than normal, driven by above normal precipitation in the preceding 3 months.  Because of this, the U.S. drought monitor hasn’t quite caught on to the situation in mid Missouri and only has the Bootheel squarely in drought mode. The 7-10 day rainfall forecast does not look promising for rectifying this drought situation, and exposed soil cracks (which already reach China) look to get even wider and deeper.  

Quick Hit

  • Drought Stress: As if I haven’t said enough about it already, non-irrigated turfgrass is in drought survival mode.  This has led to some homeowners believing they have a disease, when in reality tall fescue and Kentucky bluegrass are in an extreme water stress situation and even more drought tolerant zoysia and bermudagrass are feeling the extreme pinch.  If this is combined with a late spring nitrogen application, the plants are trying to cash leaf growth checks that their roots and low soil water conditions can’t afford. 

    Even turf managers/homeowners who are irrigating may not be able to keep up.  We’ve been losing 1” a week by low evapotranspiration estimates, which is a mere ~ 9,051 gallons of water per 1/3 acre lawn.  If a 70% replacement were considered the rule, then 6,336 gallons of water would be needed for each of the last 4 weeks.  Very few, if any, have been doing this to a lawn.

    Remember the best irrigation is accomplished by the early bird.  Watering in the early morning hours is the best strategy, because it rinses dew and guttation fluid off the leaf blade and disrupts the turf disease cycle.  Watering lawns and landscapes during the heat of the day can cool the plant briefly, but is inefficient and can spark significant disease outbreaks.  Two – three deep 1/4–1/3” irrigation events a week will be necessary to keep growing turf healthy during this extreme period.

  • Localized Dry Spot:  As noted in the previous update, golf course greens with water repellant soils have been a struggle if not impossible to manage in this extreme period.  Golf greens afflicted with this problem should apply wetting agents or penetrants on a routine basis to combat the problem.   

  • Japanese beetle catches: Japanese beetles have arrived in Missouri well before their normal July 4th time frame.  Catches have been reported in St. Louis, Springfield, and Columbia over the past week and the numbers are steadily growing.  These first catches are the clue that grub control will be needed in the next few weeks.  I have been asked if more than one grub control application will be necessary this year, and at this point I don’t think so.  However, it may need to be made earlier to catch grub outbreaks that should occur 3-4 works earlier than normal (which would be in mid July instead of mid August).  As the Japanese beetle numbers climb, watch your roses, lindens, and other landscape plants. 

Rusts - Galvanize Your Turf

Stem rust occurring on Kentucky bluegrass in Missouri.

This drier than normal weather pattern doesn’t favor turf disease, and the diagnostic lab has been busy receiving drought stressed plants rather than instances of true disease outbreaks.  Rusts are one disease pathosystem though, that rather likes the dry.  I normally observe this disease in early fall, but rusts are occurring en masse in late spring/early summer this year.  A number of different rust pathogen species can occur on turf, and all turf types are susceptible to at least one of these rust pathogens. 

The most common rust diseases in this region are stem rust caused by Puccinia graminis and leaf rust caused by Puccinia coronata.  These pathogens differ in that P. graminis prefers higher infection temperatures than P. coronata.  Current outbreaks have been identified as stem rust caused by Puccinia graminis.  This pathogen is also a major pathogen of wheat, and has an interesting life cycle that includes two spore stages on barberry (alternate host) and two spore stages on wheat or in this case turfgrass (primary host).  The orange spores in which the rust disease gets its descriptive name are called urediniospores, and erupt from leaf tissue in concentrated areas termed pustules.  Thousands of urediniospores can erupt from a single pustule, and hundreds of pustules can occur on a single leaf blade, causing considerable damage to the plant.

Stem rust is such a devastating wheat disease that a barberry eradication program was initiated to aid in disrupting the disease cycle and controlling the disease.  Interestingly, I had a barberry in my lawn.  It’s a rental home so I couldn’t remove it, but the lawn care company took it out just last month.   

Back to the turf world, Kentucky bluegrass is most severely affected turfgrass by stem rust.  Earlier last week, I noticed a rust species infecting zoysiagrass too, but since zoysia is a warm season turfgrass no damage was occurring.  Tall fescue is normally affected by a leaf rust in the fall, doing minor damage in lawns but can be a prevalent problem in pastures.  I’ve just received a call indicating rust may be occurring now in tall fescue as well, but there is no confirmation.        

The key to rust prevention is that the disease occurs much more prevalently and severely on stressed plants.  As noted above, drought stress is prevalent and a predisposing factor to rust occurrence.  Proper irrigation, mowing height, fertilization, and shade reduction will help prevent and lessen this disease.  The disease does need leaf wetness to infect so rinsing dew and guttation fluid off leaf blades with early morning irrigation will aid in reducing this disease.   A light fertilization (0.1 – 0.2 lb N/1000 sq ft) may aid in rust recovery, but this can come with an extreme cost of increasing other summer diseases and is not recommended at this time for cool season turf.  Host resistance can also play a role in preventing this disease – (current NTEP ratings for Kentucky bluegrass cultivars can be found here).   Lastly, fungicides are normally not recommended for rust outbreaks in turf unless especially severe.  Fungicides in the sterol biosynthesis inhibitor class (aka DMIs) are considered most effective against rust diseases.          

New Student Joins the Mizzou Turf Pathology Team

New graduate student in program working on Pythium project

The Missouri Turf Pathology Program welcomed its fourth member yesterday in graduate student John (JB) Workman.  JB joins us from the University of Georgia, where he obtained his Masters degree under the direction of Dr. Clint Waltz with a thesis entitled “A holistic approach to decreasing dollar spot severity and overwintering inoculum of Sclerotinia homoeocarpa.”   JB is a native of Hartwell, GA, and has many years of experience in the golf industry and some genetic lineage, with his father being a superintendent and his mother being the executive director of the Georgia GCSAA chapter. 

JB will be conducting dissertation research to characterize and develop management practices for the most prevalent Pythium root diseases affecting bentgrass greens in the Midwest (or Mid-South, or whatever Missouri is these days).   Considerable confusion exists in this region as to which Pythium root disease superintendents should be focusing their management efforts on:  Pythium root dysfunction or Pythium root rot.  The two distinctly different diseases are caused by different Pythium spp. and occur at different times of the year, making identification crucial for effective control.

This project was funded through the Environmental Institute for Golf/GCSAA Chapter Cooperative Program with the Heart of America, Ozark Turfgrass Association, and Wisconsin Chapters all pledging funds to support this research project.  We are pleased to have JB on board to facilitate this important project and shed light on this important problem.       

Save The Date: July 10th
University of Missouri Turf & Ornamental Field Day

-  Want to see Dr. Starbuck discuss trees for the last time before his retirement? 
-  Want to meet JB in person and hear more about the Pythium project? 
-  Want to find out about the latest and greatest methods for turf and ornamental management?
-  Want to meet local vendors interested in providing management solutions?
-  Or, do you just want to eat a great lunch among your colleagues and research scientists?

Well then, come on over to the research farm on July 10th for all kinds of interesting lessons and information on how to effectively manage turf and ornamentals in Missouri.  Our outstanding lineup of presentations and displays is set, and our research teams look forward to meeting and discussing your plant management practices.  Look forward to seeing you there!!

Click here to see the full schedule.

Click here to register.


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