ALL: When do you apply fungicides for large patch control on zoysiagrass?

Single Fall
Single Spring
2 Fall
1 Fall and 1 Spring
2 Fall and 1 Spring

Update (09/22/2016)

One Swing Should Wait til' Spring

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Soggy September

  1. Temperatures have been sporadic this month. - Source: Pat Guinan
  2. Over the last 7 days, intense rainfall has occurred in the region. - Source: Pat Guinan


Both by meteorological and astronomical standards, fall is in force today with the arrival of the fall equinox.  It sure doesn't feel like it though, as temperatures have averaged 6-8 degrees above normal in in much of the region over the last 7 days, due to a stagnant jet stream over Canada. As obviously noticed, photoperiods will continue to get shorter until the winter solstice on December 22nd, when the approximately 9.5 hour daylength will start to expand once again.  With the current heat wave, the shorter daylength (currently just under 11 hours) has a profound effect on reducing stress on cool season turfgrasses and putting warm season species such as bermudagrass and zoysiagrass down for their winter's nap.  Some concerns have been raised over potential cool season seedling damage from the high heat and potential disease activity.  At this point, we haven't noticed any problems, and last week's cool temperatures and rains should still be aiding quick establishment.

If seed and fertilizer were applied previous to it, last week's rains were ample enough to get seed off to a good start… that is if the seed didn't float away as may have been the case in Columbia.  Precipitation totals are above normal, but variable across the state (0.6, 1.18, 2.62, and 4.75 inches above normal in Springfield, KC, STL, and Columbia respectively).  At the MU turf research farm, we have been itching to seed a few new areas, including a perennial ryegrass NTEP trial and Kentucky bluegrass plot, but the weather just hasn't allowed us to get in the field.  A 3-day rain event on Sept. 8-10 dropped 4.46 inches of rain, which was quickly followed by an additional 2 inches from events on Sept. 14 and Sept. 16.  A soggy September is following the precedent set by July and August.

6-10 Day Forecast: Little more heat and rain expected to close the month

  1. Warm temperatures expected to stick around at least into the weekend. - Source: NOAA CPS
  2. Rainfall chances rise as we get into next week. - Source: NOAA CPS

Quick Hits

Rust Outbreaks Still Observed

  1. Stand symptoms may include dark brown spots along with orange rust pustules.
  2. Individual pustules contain 1000s of spores, which spread quickly from plant to plant.

  • Rust: A sample from a Kentucky bluegrass lawn in the Springfield area was submitted late last week with a considerable amount of stem rust.  This disease is normally most severe on younger turfgrass stands, and those that are impacted by drought.  In late May, a significant rust outbreak was also observed in a Kentucky bluegrass sports field in Columbia.  Rust is also considered a “low nitrogen” disease, so at this point fertilizing with 1 lb N/1000 sq ft will help either Kentucky bluegrass or tall fescue recover, potentially without the use of fungicides. If fungicides are deemed necessary, the QoIs (i.e. Heritage, Insignia) or the DMIs (i.e. Bayleton, Banner) are suggested.

  • Pest Management for Home Lawns Booklet

      This pocket-sized booklet covers the most common weed, disease, and insect problems in home lawns. Information includes identification and management tips, with emphasis on both cultural practices and pesticide recommendations for control.

  • Pest Management for Home Lawns Booklet:  Want a bit of MU expertise in your pocket when managing either your lawn or your client’s?  Want to train your staff on identification and biology of common lawn species and their pests?  Need a quick reference guide for fungicide, herbicide, or insecticide activity? A collaboration between Dr. Brad Fresenburg (weeds), Dr. Bruce Barrett (insects), and myself (diseases) has produced a definitive, yet brief guide for lawn pest management. This useful resource is a pocket, or glove-box, sized manual with a durable laminated cover that can be with you on the go and take the knocks of the common work day.  We hope you can make good use of this new resource. Click here for more information.

  • Aerification/Seeding/Fertilization: As mentioned in the previous update, the window is open for fall renovation, but we are getting into the tail end of it. Although steamy, the rest of this week and weekend, prior to next week’s cool down and potential rain event, would be a very good time to put down some sweat on cool season turfgrass areas. Pay attention, however, that you aren’t doing more damage than good by creating compaction in muddy areas with equipment and traffic. As far as fertilization goes, now is the time to feed cool season turfgrasses. Dr. Brad Fresenburg has developed a fantastic web based application that will help determine the amount of fertilizer required for a certain area, including a link to a GPS referenced area estimator. Designed for homeowners, but can be a very handy tool to check your own applications. Check it out at

One Swing Should Wait til’ Spring

Large Patch Flares in Fall

  1. Large patch has flared up considerably in mid Missouri after recent rains.
  2. Orange flagging symptom of individual zoysia plant along a large patch margin.

As the pendulum swings to fall, large patch symptoms on zoysiagrass have flared up again.  Last week's cool temperatures along with the heavy rainfall in Columbia (as noted above) has resulted in numerous large patch outbreaks at the MU research farm and two lawn samples sent into the Clinic.  Symptoms can appear diffuse as small infection centers at this time of year, or as the more regular patch symptom.  Although not as prominent as in the spring, the characteristic symptom this fall is an orange flagging of infected leaves on symptomatic plants.  When the pathogen is really chugging, this flagging will result in a burnt orange, or firing symptom on the margins of infected areas.

In a month or so, depending on the weather, zoysiagrass will go dormant and symptoms will be indistinguishable.  Now, however, is time to come up with a game plan of how to deal with both fall and spring symptoms.  Scout zoysia areas and determine where outbreaks are occurring.  Determine your fungicide strategy.  If three fungicide applications are in your plans, the current suggestion is an application now (or even earlier) followed by another later this fall 21-28 d later in October, and another in early spring.  Suggested 2 inch soil temperature threshold targets are a fall to near 70 F in September (lowest has been 74 F in Columbia hit last week) and a spring to 50-55 F in early to mid-April.  Based on our research, a two application strategy should include a fall and spring application around these two thresholds. 

If limited to a single application based on budget and/or client willingness, perhaps the best method is to simply scout out the affected areas now and identify the problem.  Then follow up next spring in early – mid April (even while the zoysia is dormant) with an early preventive application.  Spring large patch outbreaks, particularly during wet Mays, tend to cause the most devastating damage in this region of the upper transition zone.  Preventing the disease from gaining a foothold early in the spring can get the zoysia through the prime infection period until the heat of summer kicks in and the zoysia can fend off the pathogen on its own. We've demonstrated fall applications (click here to read a previous report) are more erratic for spring control, and may require a rescue treatment.  If only allowed a single use of the hammer, it would be wise to wait until spring to swing. 


Lee Miller
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Extension Turfgrass Pathologist
University of Missouri