Golf: When do you have your first Pythium root rot application scheduled?

Early April
Mid April
Early May
Mid May
High forecasted temperature
High forecasted precipitation
No Preventive Applications

Update (4/5/2019)

The Spring Hall Monitor

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Cool March Yielding to Cool April?

  1. March temperatures hopped around, but ended up below normal. - Source: Missouri Climate Center
  2. Through mid April temperatures are expected to remain slightly below normal. - Source: NOAA

March 2019 ended cooler than normal for much of the region with temperatures 2-4 degrees below average. This continues the February trend, which also finished nearly 2 degrees below average in Missouri. A quick spring warmup in the first half of April doesn't seem to be in the cards, as forecasts indicate a continued below normal temperature pattern for the next few weeks.

While cooler than normal temperatures have resulted in a nice gradual start to spring, heavy precipitation, particularly along the Missouri river corridor, have thundered in saturated soils and a series of unfortunate flooding events throughout the region. Miserably for many, this consistent rainfall pattern isn't forecasted to let up through the early part of April. Mowing has begun on cool-season grasses in much of the region. Be mindful of soil conditions prior to mowing, as wet, heavy soils compacted now will limit root growth and development during the trials of the summer season. Soilborne diseases like summer patch are also much more severe on compacted sites.

Wet March Weather Forecasted to Continue in April

  1. March precipitation was above normal in the Missouri River corridor. - High Plains Regional Climate Center
  2. Forecast doesn't indicate a dry down through mid April. - NOAA

Quick Hits

Yellow Patch Sighting
Infection by R. cerealis noted on a creeping bentgrass putting green.

  • Yellow patch, or cool-season brown patch, caused by Rhizoctonia cerealis has been noted on creeping bentgrass putting greens over the last two weeks. Damage from this disease is usually minor, and bentgrass normally grows out of the symptoms when warmer spring temperatures arrive. This disease can be confused with Microdochium patch, which can continue to cause damage and turf loss, so be certain of the diagnosis.

The Spring Hall Monitor

Slow and Steady Spring Wakeup

  1. Forysthia blooming in the region.
  2. Crabgrass pre-emerge applications should be occurring now. -

No one is running in the hall this spring, but everyone seems to be getting to class on time. While temperatures have been below normal for the last two months, they are slowly rising as daylengths are getting longer. Cool-season grasses are greening up, and several indicators are signaling it's go time for weed preemergent application. These include:

  • Forsythia bushes around town, and in front of my office, are blooming.
  • Growing degree day models (which can be found at are at prescribed thresholds for application.
  • Soil temperatures are slowly rising and have eclipsed the 50-degree F mark at the two-inch depth.

Soil temperature graphs at four locations in the state are shown below with the 55 – 60 F threshold for preventive fungicide applications for fairy ring on putting greens highlighted. While still plenty of time left in April, contrast the comparatively smooth incline of soil temperatures this year to previous years of 2018 and 2017. Thus far, we are not experiencing the wild swings of the previous two years… a certainly welcome change. Root development of cool season grasses from a temperature standpoint would be good this spring, however, the constant saturation of soils may limit oxygen availability and restrict overall root depth.

Slow & Steady Rise

  1. Springfield: Current 5-d average = 49 F
  2. Columbia: Current 5-d average = 48 F
  3. St. Louis: Current 5-d average = 48 F
  4. Kansas City: Current 5-d average = 45 F

Below are a few notes on specific diseases that will require attention and monitoring over the next few weeks.

  • Large patch on zoysia fairways and lawns – This wet weather pattern is shaping a severe season for this disease, and this weekend's warmup will likely get large patch pressure cooking. With the amount of rain the region has experienced, I expect fall fungicide applications may not be entirely sufficient for control and spring applications may be necessary. Three things to consider for maximizing large patch control this season…

    1. Particularly in previously untreated areas prone to large patch outbreaks, apply early, probably in the next week or two. Our research shows early applications made at a 50 F soil temperature threshold (which we'll get back to this weekend quickly) work better than later in the spring.

    2. Increase your water carrier volume if currently spraying at 0.5 – 1 gallon/1000 sq ft. If managing a large acreage of zoysiagrass (i.e. golf fairways), identify your hotspots rather than spraying everything. This reduced acreage should allow application at a higher 2-4 gallons of water/1000 sq ft. This will drive fungicide deposition lower in the canopy, which is crucial since the large patch pathogen infects at the stem base or leaf sheath and not the upper foliage. Research demonstrating this was conducted by Dr. Jesse Benelli when at University of Tennessee under the advisement of Dr. Brandon Horvath. See the research here.

    3. Despite what the old wives tell you, nitrogen does not increase large patch severity, and when applied in spring might actually reduce it. Over the course of several field experiments individually at MU and with our colleagues at Kansas State (Dr. Megan Kennelly, Dr. Jack Fry, et al.) we have found absolutely no correlation between increased large patch severity and nitrogen application during the infection period. In our most recent work, we demonstrated a small 0.5 lb N/1000 sq ft spring application when 5-day 2" soil temperature averages reached 65 F sparked zoysiagrass growth and lessened large patch symptoms. See this just published research here.

  • Fairy ring on golf greens – As discussed ad nauseum in previous reports, target the 55-60 F threshold for the first preventive application and a subsequent application 28 days later. Increased forecasted air temperatures over the weekend, particularly nighttime temperatures in the 50s, will likely push soil temperatures into this application threshold for much of Missouri next week. For more information, select any previous April report from the disease report index.

  • Pythium root rot on golf greens – Check your drainage and organic matter now! If water isn't moving out, root development will be compromised. This wet weather pattern may drive Pythium root rot infection regardless, particularly if precipitation continues into the warmer stretches over the next few weeks. On greens with a history, watered-in preventive applications may need to start in mid- to late April as opposed to waiting until May.


Lee Miller
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Extension Turfgrass Pathologist
University of Missouri