LAWN: Have you put a second split preemergent herbicide application down yet?

No - but will
Yes - and make three split apps
No - only make one app
Don't apply preemergents

Update (5/14/2019)

The Spring Pythium Ninja

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July 30: Field Day Registration Now Open!

Come join us for the 2019 Mizzou Turfgrass & Landscape Field Day to be held on Tuesday, July 30th at South Farms in Columbia, MO. We will serve up an education filled day along with the comradery of your fellow turfgrass industry professionals over morning doughnuts and a delicious BBQ lunch. GCSAA CEUs and other horticulture accreditation points will be offered. Learn the latest, improve your turfgrass management game, and share some laughs. What better way to spend your day?

Attendees, sponsors and exhibitors can all register by visiting:

A little different portal and login, but 2017 was so two years ago. We also still have the previous website to list sponsors and quickly update more detailed information -


Not the May of 2018

  1. May temps are much slower out of the gate than last year. - Missouri Climate Center
  2. 6-10 day outlook: Warmup expected later this week into next. - NOAA

After a cold February and March, April 2019 was a little over a degree above average in Missouri. Although a considerable warmup is predicted, May has flipped to a few degrees below average in most of the region. This cooler, wet May has slowed warm-season turfgrass greenup greatly (see below), but has caused a boon of growth and coverage in tall fescue and/or Kentucky bluegrass lawns and sports fields. Temperatures are expected to rise significantly over the next few weeks with a warm up into the middle to upper 80s approaching the weekend. Perhaps even a smidge of sunlight will stick around for more than a fleeting moment. This warmth will feel like a cool breeze compared to the sustained heat of May 2018, which as a reminder was the warmest ever on record.

Although it certainly didn't feel like it, April ended 0.59" below the statewide average, but don't tell that to those around the Bootheel and northern AR where 4-6" were common. Intense rainfall hit a fever pitch in late April and May, where some areas near Kansas City and western MO have received 6-8", whereas other areas are nearer to 3.5-5". May is normally the wettest month in the region, with over 5.13" being normal for the month. With very low evapotranspiration and persistent cloud cover, soils are saturated, making it difficult for our farming friends to get crops in the ground. On turfgrass stands, soilborne pathogens can and will prosper in these late spring, saturated conditions. A dry down later this week is expected, but a rebound of precipitation chances is forecasted over the next six-ten days.

Rain, Rain Set to Go Away?

  1. Much above normal precipitation from I-70 south over the last 30 days. - Missouri Climate Center
  2. 6 - 10 day outlook: Expect the rainy pattern to continue next week after a slight dry down. - NOAA

Quick Hits

  • Lawns: All is quiet on the lawn front, except weed issues and some feared compaction from heavy mowers on saturated soils. On Kentucky bluegrass, this could be a very severe summer patch season because of this compaction and prime environmental conditions. Nutsedge is loving the wet weather and is now emerging, which is bad for everyone. Where weed control resources are concerned, there's no better one out now than the Purdue-led Turfgrass Weed Control for Professionals which is now in its brand spanking new 2019 edition.

Winterkill Questions Should Be Answered Soon

  1. This low area of two year old 'Meyer' zoysia after our wet winter and spring.
  2. Also having concerns about this 'Patriot' bermudagrass research area.

  • The Still Too Early Winterkill Report: Winter may have been beaten back in the Game of Thrones (oops, spoiler alert!!), but warm-season turfgrasses are having a difficult time doing the same this spring in MO. Sustained rains, lack of sunlight, and cool temperatures unfortunately haven't made for great warm-season turfgrass growth and recovery. We are starting to see recovery in areas previously thought gone, but we might expect some attrition in heavily saturated and shaded zoysiagrass bermudagrass. If needing to estimate replacement, wait until 80+ degree highs and 60+ degree lows occur over the next 7-10 days before for zoysiagrass, and perhaps a little longer into late May for bermudagrass. Maybe a few buildings instead of the whole city will have to go?

  • Dollar Spot Observations & Predictions on Bentgrass: Dollar spot exploded on our bentgrass research plots on April 29, and sprung into full action for most of the region in the first full week of May. The Smith-Kerns dollar spot prediction model (click here for the Threshold Charts and select your closest city) "went off" on May 2 & 3 with 24% and 34% probability in Columbia, MO. Compared to associated reports on golf courses this seems to be very accurate to actual disease occurrence in much of the region. On our research green, with a huge inoculation load and low nitrogen the model got to 15% on April 25 and 25, suggesting cultural practices and pathogen abundance play a role.

    Compared to our graphs, some of the other widely available Smith-Kerns model outputs may yield different results. Weather data will be variable from one station to the other depending on microclimate, but the differences in this case were striking. In talking with several colleagues, some of the online services may use a modified version of the Smith-Kerns model that don't incorporate the rolling 5-day averages in the original, hence the numbers are inherently larger but the overall movement of the model is the same. Bottom line, pick a service and stick with it to potentially save an application, two or three. Incorporate a small, out of the way indicator area to judge the model outputs vs. your actual disease severity.

Phytotoxicity & Waterlogging

  1. Misapplication of herbicide or overregulation with PGRs have been slow to recover.
  2. Although the bronzing appears ugly, most new growing tips aren't affected.

  • Phytotoxicity & Water Logging: A few bentgrass samples have been submitted with abiotic stress caused by a combination of phytotoxicity from plant growth regulator (PGR) and/or herbicide application, heavily saturated soils and skies with persistent cloud cover. A combination of PGRs with some micronutrient fertilizers that also carry a dose of gibberellin or similar might double dose slow growing bentgrass into becoming a no growing bentgrass. Landscape plants, presumably without the additional stress of a chemical application, have also been observed with general chlorosis due to prolonged wet feet.

    Diagnosis of this issue is difficult based on symptoms alone unless a clear line of application is noticed as in the above picture. With a hand lens or compound microscope, the growing tips of plants are fine but older leaves may appear burned or bronzed. In most cases, the bentgrass will grow out of symptoms with a little nitrogen and sunshine love, but depending on the product (particularly if a herbicide) root growth inhibition may be a concern.

Large Patch Firing

  1. Large patch will fire up in any low, wet area, including an accumulation of divots.
  2. More typical large patch symptom with firing margins.

  • Large Patch Raging: Wet, cool conditions have caused unchecked large patch disease to show its teeth. Several reports and observations of characteristic firing margins have been rolling in from Arkansas on up through Missouri as zoysia very slowly greens up. An interesting case was observed on a driving range where the lower divoted areas accumulated water and sparked an outbreak. Fungicides such as Heritage, flutolanil (i.e. Pedigree), and tebuconazole may be necessary to stop the damage from occurring further in a curative situation but won't magically bring damaged zoysia back. In damaged areas, nitrogen should be applied at a light 0.25 or 0.5 lb N/1000 sq ft rate along with fungicide to encourage recovery.

Golf Greens: The Spring Pythium Ninja

Pythium Root Diseases on Greens in Late April/Early May? Yes.

  1. Pythium root dysfunction observed as chlorotic, mottled areas on putting greens.
  2. Numerous oospores, some bisporous, indicate root dysfunction in affected areas.

Pythium root diseases along with the first symptoms this spring have been diagnosed on creeping bentgrass greens in the region. Pythium oospores have been observed in roots, which isn't devastating in itself, unless observed in association with declining roots, encysting zoospores, and symptoms. This combination was exactly the case on samples submitted from western Illinois, St. Louis and Springfield the last two weeks. Three of the four submissions had bisporous oospores and the roots lacked root hairs, indicating Pythium volutum, the cause of Pythium root dysfunction (not the typically observed Pythium root rot) was at least joining in the party. All greens were sand-based and well drained, and two of the greens were young, while the other was in its late teens (17 years old).

A preventive strategy based on a rotation of watered in applications of Segway (high labeled rate), QoI fungicide such as Insignia (high rate), and a non-watered in Signature + Subdue Maxx or Banol is recommended for Pythium root dysfunction control. If curative apply every 14 - 21 days based on symptom appearance, applying Insignia as the QoI fungicide. Relieving stress by raising mowing heights and increasing nitrogen levels is also crucial to symptom recovery. While Pythium root dysfunction can also impact well drained soils, mind drainage and make sure water is moving through the profile now before summer hits... because heat + stagnant water hurts. For more information on Pythium root dysfunction, see

Soilborne diseases, particularly Pythium type, move silently and without notice in the soil and along root surfaces. Like a ninja, they slowly take out creeping bentgrass roots, while unsuspecting stares slide admiringly across a green putting surface. This characteristic makes these diseases extremely difficult to diagnose without the aid of a skilled diagnostician, and lean more heavily on preventive control when a history has been established. If you suspect or observe odd bentgrass response or patchiness on your greens in the relatively mild spring weather now, send them to a diagnostic lab to get checked. Get ahead of the summer swelter and protect your root investment before the weather recession hits.


Lee Miller
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Extension Turfgrass Pathologist
University of Missouri