SURVEY QUESTION

ALL: Are you observing zoysiagrass that has winterkilled?

Yes - Significantly more than in previous springs
Yes - Damage is normal and slight
No - But I am seeing significant large patch outbreaks
No - Zoysia is fine

Update (4/23/2019)

Panic or Patience?

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Weather

An April Spark

  1. April temperatures sparking plant growth. - Missouri Climate Center
  2. April thankfully much warmer than last year. - Midwest Regional Climate Center

April 2019 luckily has not been the April of 2018, which recall was the coldest in recorded weather history around the region. Wildly fluctuating temperatures are trending 2-3 degrees above the April average, sparking wondrous redbud flowering, large morel finds, crabgrass germination and zoysiagrass greenup. Temperatures are expected to stay above average throughout the end of the month.

Precipitation has relaxed a bit in the last week in the western part of Missouri, while the east including St. Louis and the Bootheel recieved another 1-2 inch rainfall event. Over the previous 30 days (http://climate.missouri.edu/mcw/) this trend has been persistent, with St. Louis 2-3" above normal and Kansas City at or just below average for precipitation. Rainfall chances continue to be above average through the end of the month in MO and KS, with perhaps a dry down in store for AR.

Continued Warmth & Rain Through The Week

  1. Much of the region and country expected to stay warm through April. - NOAA
  2. Rainy pattern expected through this week, with more variability towards April's end. - NOAA

Quick Hits

Spring Freeze Chance Presumably Over
MU IPM Frost/Freeze Guide & current forecast indicates chance for a killing frost is probably over.


  • Frost Chances Quickly Diminishing: Although nothing is certain in MO weather, according to the MU Frost/Freeze Guide and the forecast, the chances for a significant spring frost event at this point are slim. The guide shows that for most of MO the median date when 32F or below occurs is past, and 28F or below is several weeks past. So plant those annual flowers if you got them.

Pythium in April? Yes.

  1. Pythium blight evident on a poorly draining green near STL.
  2. After incubation, copious amounts of Pythium mycelium observed on leaves.

  • Pythium blight isn't seen often on putting greens, but when it is observed it can be spectacular (for a pathologist). A sample was sent from a poorly drained Poa/bentgrass green near St. Louis. The disease was primarily on the bentgrass, leaving the Poa annua unscathed. When a disease is responsible in a mixed stand of grass species, it normally will infect one species and not the other. In most cases, however, the Poa takes it on the chin (i.e. anthracnose or summer patch) and not the bent. Observing Pythium spp. infect the foliage this time of year is rare, but remember we had the wettest winter since 1984-85 and this spring hasn't let up in St. Louis with consistent rain. Observing this this disease on an established bentgrass putting green is also rare.

    In this rare instance, a knockdown of Segway, Banol, or similar is suggested. For all superintendents, however, it should sound a warning bell that prevention of the more nefarious Pythium root rot should occur sooner rather than later in these wet conditions, particularly on high organic matter or poorly draining greens. Light, inconsequential Pythium infection sites have been observed on white, healthy root systems this spring, and might only be a matter of time before these turn into a problem and rob plants of vital root function.

  • Soil temperatures are slowly rising and the Smith-Kerns model is teetering towards a dollar spot warning threshold every now and then in the region. We have created a page to easily monitor both in Missouri, with a single click on the Threshold Charts section of the website. Select your closest city to view a soil temperature chart that catalogs daily and 5-day average 2" soil temperatures with 55-60F threshold denoted for fairy ring prevention and the results from the Smith-Kerns model for dollar spot probability with the commonly used 20% probability threshold. We will make refinements over time, but this is a good way to keep track of the MO environment and perhaps save an application or two over the course of the season.

Waiting for Zoysia Greenup: Panic or Patience?

Conspicuous Zoysia Issues

  1. The first symptoms of large patch evident late last week.
  2. Concerns of zoysia winter kill abound in the region.

Several reports in the last week have expressed extreme concern over the lack of zoysia greenup, and the potential for large amounts of winterkill on some golf courses and home lawns. As mentioned previously, the 2019 winter was the wettest since 1984-85, and the 5th wettest on record. Low lying areas, those in shade and on northern facing slopes are the most impacted presumably due to prolonged ice buildup and anoxic conditions. Some of these areas have "the smell of death" associated with sulfur and methane production of anaerobic bacteria. Perhaps not as important (!), we have also observed our first hint of large patch infection at the research farm on untreated plots.

Although some minor attrition of 'Meyer' zoysiagrass has occurred in low lying areas since 2010, for the most part the variety has endured many a hard Missouri winter. The polar vortex of 2013-14 severely impacted much of our warm-season NTEP trial (https://turfpath.missouri.edu/reports/2014/update05_08_14.cfm), but 'Meyer' was one of the few varieties that persisted.

There is still time for zoysiagrass greenup and recovery, and most of the reports are from mid-Missouri and St. Louis where wet soils still predominate. These wet soils are colder soils, (compare St. Louis and Kansas City in the Threshold Charts) since soils with water-filled pore space hold temperature much more tightly than air. In some instances, perhaps a little time and dry down will let zoysia recuperate.

Since this is uncharted territory for us, we are conducting a quick field experiment to investigate methods of recovery, or at least assess if the stand is dead.

Current suggestions include:

  • An application of darker topdressing sand, or a pigment, to warm areas more quickly and allow for a better gauge of winterkill severity.
  • Rake, drag, or conduct a very, very shallow verticut to break up the tight layer of interweaved brown stolons and allow for further soil warming.
  • If winterkill is feared at your facility or lawn, pot and place a sample indoors by a window to warmup and hopefully greenup. Give it 7-10 days to perk up prior to making the call for replacement.

SAVE THE DATE!
July 30, 2019 – MU Turfgrass & Landscape Field Day

Plans are underway for the 2019 Mizzou Turfgrass & Landscape Field Day. The event will be held July 30 at our research facility at South Farms. Registration for vendors and attendees will be available shortly.



Lee

Lee Miller
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Extension Turfgrass Pathologist
University of Missouri