All: Have you applied a preventive fungicide for large patch or spring dead spot yet this fall?

Only apply in spring
Don't apply preventives for either disease

Update (10/11/2017)

Prepare for Spring Ghouls

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Red October Expected to Continue

  1. Early October temperatures are well above normal. - Source: Pat Guinan
  2. After today’s brief cool down, warmth expected to return. - Source: NOAA

Fall began as an Indian summer with a warmer than normal September, and has followed suit throughout early October. Temperatures throughout the state are 8-11 degrees above normal thus through October 9, and withstanding today’s current cool down look to get warm again into this weekend. The current longer term 8-14 day NOAA forecast indicates continued warmer than normal temperatures, which would make October 2017 eerily similar to the last - the 10th warmest October on record and the hottest since 1971.

Increased rainfall events in October are a welcome change from September’s drought pattern. September ended with deficits ranging from 3-5 inches across much of Missouri, so the current rainy pattern of early October (1-2 inches over much of the area) are helping. As noted below, the rains should help out with cool season turfgrass seeding, which was difficult with the lack of rainfall. As with the warmth, the trend of increased rainfall also looks to continue in the 8-14 day NOAA forecast.    

October Rain Replacing Sept Deficit

  1. Early October rains haven’t made up for deficit since Sept. - Midwest Regional Climate Center
  2. Forecast for next week indicates more wet weather. - Source: NOAA CPS


Quick Hits

Rainfall Welcome

  1. Supplemental irrigation needed to get cool season turfgrass to sprout. - 9/29
  2. On the flip side, excessive rainfall wasn’t impeding sod harvest at all.

  • Recent October rain events over the last 10 days have certainly helped both establishment and growth of cool-season turfgrasses. A few more weeks and forecasted warmth are available for seeding and fertilization, but the time is now to take advantage of it. The above picture from SelecTurf sod farm in Jefferson City demonstrated the clear need for supplemental irrigation in getting tall fescue seedlings to establish through September. Sod harvesting, however, was in full swing and not inhibited at all by wet weather. Thank you to Jim Keeven for showing me around his impressive sod farm operation.
  • If the seeding is done, don’t forget about weed control. If herbicide use is planned, the best time for control of troublesome perennial or annual broadleaves is the fall. Some winter annuals are farther along than normal now, so this would be an appropriate time to take them out.

Disease Pressure on Bentgrass Persists

  1. A 3 for 1 - fairy ring + dollar spot + red leaf spot.
  2. Spores of Drechslera erythrospila on a bentgrass sheath.

  • Even through this cool spell, there is no time to sleep on disease control on bentgrass putting greens. We’ve observed a marked increase in dollar spot, fairy ring, copper spot and especially red leaf spot on our research greens in the last few weeks and it will take a few more sprayer trips to put greens to bed yet this season. With the recent wet weather, we’ve also noted an uptick in algae occurrence, a subject I’ll be discussing in more detail during the winter conference season. Now that the weather has cooled and days are shorter, the DMI fungicide class can be rotated in with a bit more confidence and lesser risk of phytotoxicity.  

Spider Webs Can Cause Unnecessary Fright

  1. Early morning fog this week caused a spectacular display of spider webs on turf.
  2. No, this isn’t a Pythium ghoul. Just a steady mat of busy spiders.

  • The heavy dew this past Monday reminded us that it is October and Halloween is just around the corner.  A heavy glaze of spider webs across the MU turf farm was strikingly beautiful in the heavy fog, but to the untrained eye and quick reaction may appear like mycelium associated with Pythium blight or other maladies. Temperatures are too low for these warm weather foliar diseases, and remember that diseases don’t occur in uniform patterns but are aggregated in patches or areas of the turfgrass stand. As you can see above, our spiders provide a uniform coating of webs across the canopy to yield a spook, but no damage.

I do appreciate the nice right angle though.

Time to Prevent Warm Season Turfgrass Diseases

Prevention of Large Patch & Spring Dead Spot

  1. Five-day average soil temperatures have finally dipped below 70 F consistently.
  2. Large patch is apparent even through the spider web haze on untreated areas.

Soil temperatures are down at or just below the threshold range of 70 F for prevention of large patch on zoysiagrass and spring dead spot on bermudagrass.  In addition to Columbia, (shown above) five-day averages are currently at 65, 70, 71 degrees F in Kansas City, Springfield, and St. Louis respectively.  This cold front pushing through will cause all of these to dive below 70 today, the signal for prevention of these warm-season diseases next spring. So, if not this week than next week applications should be planned on sites with history of these diseases.

For spring dead spot, a two-application approach is advised with the first being made now and the second made 21-28 days later.  Recall, last fall above average temperatures extended well into November, and this current and forecasted weather pattern is eerily similar to 2016. Some bermudagrass managers applied fungicide applications in early September and October 2016 and experienced damage from spring dead spot April & May 2017. Even if an application is already down, don’t make the same mistake again by relying on a final fall application in early October. Instead make a late October, or even early November application according to the weather conditions and the stage of bermudagrass dormancy. Bermudagrass plots at the MU turf farm are still very green and actively growing.  As for fungicide choice, the newer SDHI chemistries, including penthiopyrad (Velista) and isofetamid (Kabuto), have worked well in our trials for control of spring dead spot caused by O. herpotricha on sports turf height bermudagrass.

Large patch control is a bit more complicated, considering active outbreaks have been occurring in some areas since late August – see previous update. Earlier curative applications aside, soil temperatures are now in a good range to attempt prevention of early disease outbreaks next spring if employing a two or three application control strategy.  As mentioned previously, however, a fall application or two is often unsuccessful in carrying the load through the following spring (it is a completely new year after all…). Therefore, an application now combined with an early spring application is often necessary on high amenity zoysiagrass areas. If only one fungicide application on a site with large patch history is planned, then let it go for now and come back next spring to prevent the disease for a longer period during a more crucial stage of the season.


Lee Miller
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Extension Turfgrass Pathologist
University of Missouri