SURVEY QUESTION

ALL: How do you apply crabgrass pre-emerge in lawn/rough height turf?

All at once - fert
All at once + fert
Split app:both + fert
1 app + fert & 1 app - fert
Other

Update (03/29/2016)

A Spring Stone for Several Birds

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Weather

Warm Yields to Cool
A. March cooled off considerably, and won't touch the record warmth of 2012. - Source: Pat Guinan
B. Approximately an inch of precipitation has fallen over the last two weeks in most areas of Missouri. - Source: NOAA


After an early warm up, spring was effectively put on hold by two frost events in the last ten days.  Except for southern regions, temperatures dipped into the high 20s effectively restricting some summer annual weed development, including crabgrass.   As noted in the previous update, this warm early March to cool weather pattern has been consistent in Missouri. The figure above show this, as the years with the warmest first 10 days in March do not result in monthly high temperature records.  Temperatures are expected to rise in early April, which should spark another flurry of turfgrass growth (zoysia is starting to green up quickly in mid MO) and perhaps a more permanent breach of the soil temperature threshold for soilborne disease control on putting greens (see below).  

Although many regions of the state saw some precipitation over the past weekend (most in western MO and Kansas City), most areas are still an inch or more below normal for the month.  Short term forecasts indicate a threat for severe storms tomorrow, but the early April forecasts indicate a high probability for another dry spell. 

6-10 Day Outlook: Warm & Dry Start to April
A. Temperatures are expected to climb in early April. - Source: NOAA CPS
B. Drier skies are anticipated along with the warmer temperatures. - Source: NOAA CPS

 

Quick Hits

Forsythia Bloom Followed by Frost
A. Forsythia bloomed in early March in most of Missouri.
B. Two frost events have occurred in the last 10 days.

  • From Forysthia to Frost: By most measures, (including those on the Growing Degree Day Tracker (http://www.gddtracker.net), we are well into, if not over the target ranges for PGR applications for Poa seedhead suppression and pre-emergent herbicide applications for crabgrass suppression.  Forsythia daffodils, and other phenological indicators substantiated the threshold measures.  So what happens when a few spring frosts come along… have we been fooled by phenology?

    I’ve read a few takes on this, and haven’t found a definitive answer. Many state the crabgrass dies during a spring frost, and the threshold gets reset.  If this is the case, it would be good news for those that haven’t gotten out their crabgrass pre-emergent yet.  To be on the safe side, however, those that haven’t applied yet may want to consider dithiopyr, which has some early seedling reach back ability.  If true, those that have applied may be wondering if they’ve jumped the gun. Rewinding to 2012 again, Dr. Aaron Patton of Purdue University wrote an article I feel is most appropriate to this year’s events (click here to read).  He states that a killing spring frost is not a guarantee, and crabgrass seedlings may not be as affected by a quick freeze since they are nestled under the turf canopy close to the warm soil. Also since the pre-emergent punch is somewhat steadily released, I don’t believe applying within the threshold window earlier this month will result in significantly reduced efficacy.  Applying earlier would have been prudent and applying very soon necessary, particularly with the warmer weather for early April forecasted. Additionally, extended crabgrass control throughout the summer will require a split application strategy in a year like this one will be necessary.

    As a guide to spring frost patterns in Missouri, Dr. Pat Guinan prepared a guide last year detailing the Frost/Freeze Probabilities based on history.  With recent (1981-2010) and further archived data (1895 on) he’s produced maps and tables to point out median dates and extreme dates of low temperature events in both spring and fall.  Since many may also be wondering when to plant annual flowers, this resource may be additionally important and useful.  The guide can be found online here – Missouri Frost/Freeze Probabilities Guide.
  • Monarch Preservation: One of our local golf superintendents, Isaac Breuer at A.L. Gustin in Columbia, made the news with an article in Golf Course Management regarding his efforts in providing monarch butterfly habitat.  Due mainly to habitat loss, monarch populations have declined drastically over recent years, and along with pollinator and bee protection, has drawn considerable attention from government agencies and universities.  Milkweed, which has been reduced due to herbicide use, is necessary along the monarch migration path, and as practiced at A.L. Gustin, the substantial out of play areas at golf courses can provide a suitable habitat for native milkweeds and summarily, monarchs.  For more information on finding a source for milkweed plants, visit the Monarch Watch website at www.monarchwatch.org or the Milkweed Seed Finder at the Xerces Society website.           

Part III: Spring Application Timing: Getting the Most Birds

Early Dollar Spot Activity
Dollar spot along with some yellow patch hit bentgrass putting research greens at the MU research farm on March 22.


A la’ 2012
, dollar spot arrived early in mid Missouri, with an outbreak occurring at the MU turfgrass research farm and at a local course in Columbia, MO on March 21-22.  Our research farm has an understandably high inoculum load, (a turfgrass pathologist resides there after all), but the parallel observation at a golf course indicates the environment was particularly ripe.  Preventive applications for dollar spot, particularly in the spring, are recommended to get ahead of the damage, which can take some time to heal, allow for the use of lower rates, and reduce the initial inoculum load.

In the previous update, I detailed the thought process behind my response to a question on applying the watered-in DMI applications on greens a few weeks ago to target fairy ring and other soilborne diseases.  An early dollar spot outbreak was worrisome to me then and was unfortunately substantiated.  We published research earlier this year (click here to read) indicating dollar spot severity was reduced season long by the watered-in DMI application strategy, particularly with triadimefon applications.  More variable, however, was the impact on when the first noticeable dollar spot outbreak occurred in treated and non-treated plots.  In 2011, extremely conducive conditions occurred between the 28-day application interval of mid April to mid May, resulting in early breakthrough in treated plots.  At that time, most superintendents would have made a rescue treatment and continued along on a preventive schedule.  In this study, we did not apply anything other than the two preventive applications, and noted a sustained reduction in severity, but not an elimination of dollar spot symptoms, compared to the non-treated control.

In summary, the spring watered-in DMI application strategy will get two (or more) birds with one stone: controlling fairy ring, and reducing overall dollar spot pressure throughout the season, but not eliminating symptoms completely.  As shown below, soil temperatures have crashed well below the 55-60 F 2 inch 5 – day soil temperature threshold.  As our outbreaks indicate, dollar spot may need to be controlled prior to the initiation of applications targeted at soilborne diseases, but an additional punch to dollar spot will be delivered when those applications are made.            

Current Soil Temperatures: Both daily and 5-d average 2" soil temperatures have dipped well below the 55 F threshold in the past 10 days.

 

Lee

Lee Miller
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Extension Turfgrass Pathologist
University of Missouri