GOLF: What fungicide do you rely on to target Pythium root diseases on putting greens?

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Update (05/26/2016)

Pool is Open for Pythium Root Rot

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Wet in the West

  1. Thus far, May temperatures have been mild. - Source: Pat Guinan
  2. Frequent storms have pounded Kansas, KC and SW Missouri over the past few days. - Source: NWS


May temperatures have fluctuated, but remained mild throughout the region.  Most areas of the state are 3-5 degrees below normal for the month thus far.  These cool temperatures have caused considerable confusion for warm season grasses, which haven’t sprung back into action quite fully this year.  This temperature pattern looks to change next week (see below) as summer temperatures are expected to ring in the first few days of June.  For warm-season grasses the heat will be welcome, particularly zoysia looking to grow through intense large patch pressure.  For cool-season grasses, the heat could spell the first arrival of heat stress and subsequent summer disease pressure.

May rainfall in Missouri has been between the have-way-too-much and the have-nots.  May is typically the wettest month for the state and those in the KC and South MO would agree with that historical observation.  Local areas around Springfield, Joplin and Kansas City are 4-5 inches above normal precipitation over the last 30 days.  Columbia and much of central Missouri is an inch or two below normal for the month, along with St. Louis, which was dry for the first part of May, but has caught up considerably in the last few days.  Significant rainfall is forecasted across the state in the next 5 days, with most again centered around the Kansas City area.  This weather pattern is the perfect setup for our first bout of summer disease activity on cool-season grasses.

Next Week Outlook

  1. Here come the summer-time temperatures. - Source: NOAA CPS
  2. Even more precipitation expected next week. - Source: NOAA CPS


Quick Hits

Red Thread Popping
Red thread has been prevalent this spring on under fertilized cool season lawns & roughs.

  • Red Thread Popping on Cool Seasons:  Over the last two weeks, we have seen an incredible amount of red thread on tall fescue and perennial ryegrass areas at the turf farm and on a few lawns.  This colorful disease is caused by The disease is caused by Laetisaria fuciformis, oftentimes along with Limonomyces roseipellis, the pathogen that causes pink patch. Circular, bleached or tan, 4-8 inch diameter patches are noticeable from a distance with pink mycelium and red “threads” (actually sclerotia observed on closer inspection. These pathogens only infect leaves and do not infect roots or crowns, so turf recovery from this disease is quicker than for many other diseases.  Like dollar spot, red thread is a low nitrogen disease, meaning occurrence is usually tied to inadequate nitrogen levels.  However, at this late date it may be best to table fertilization efforts until fall, when predisposition of the turf to more destructive high nitrogen summer diseases like brown patch and Pythium is not an issue.  If fertilizer is applied, apply a small amount (0.25 lb N/1000 sq ft or less), and use a slow release nitrogen source.  Fungicide use is usually not necessary for this disease, except in very severe cases.  For more information, also see Dr. Rick Latin’s recent post

Brown Patch Lurking
No widespread symptoms yet, but leaf lesions can be found in our indicator area at the turf farm.

  • Brown Patch on Tall Fescue Warning: Dr. Fresenburg gave a report earlier in the week that brown patch was active on areas of his lawn.  We haven’t noticed widespread epidemics yet on our prone tall fescue areas at the turf farm, but we did some scouting this morning and were able to find some characteristic lesions lurking below.  Although N fertilization should have stopped by late April, this very much signifies the time to stop throwing nitrogen on to tall fescue.  The current and impending rains along with the warm temperatures expected next week should cause this disease to bust next week.  As stated in a previous posts, current research indicates over-the-counter fungicides commonly targeting the DIY homeowner are ineffective.  Products containing a QoI (or strobilurin, i.e. azoxystrobin), have provided the best control.  If a homeowner has a history of this disease on the lawn and desires a fungicide application, this would be the time to make it.  An additional application or two may be required on a 28 day interval.  When the brown patch damage is done in late July or August, the money spent on a fungicide may be better used towards reseeding.

    MU Softball Regionals

    1. MU Grounds Crew dragging softball infield. Look close and you’ll note an especially supportive crew member.
    2. Just prior to the first pitch of potentially the last game at University Field.

    • Last week, I was afforded the opportunity to play in the dirt and assist Dr. Fresenburg and the MU grounds crew in preparing the field for the collegiate softball regionals.  Jerry Cummings does a wonderful job with the softball field and by all accounts is an integral part of the team.  Happily, the softball team dominated the field, (pun intended), amassing a 26-0 margin in 3 games and winning all games by the run rule.  Sadly, while we look forward to the construction of the new stadium, this was perhaps the last game at University Field a place where blood, sweat, and a lot of laughter was amassed.  Kudos to Jerry, his staff, and workers for providing such a great playing surface for so many years. Go Tigers this weekend and beat Michigan! 

    Prevent Pythium Root Rot from Diving Into Your Pool

    Pythium Root Rot Conditions Prevalent

    1. Despite what the sign says, the Pythium root rot street is just beginning.
    2. Pythium oospores (indicated by yellow arrows) from bentgrass root submitted in mid May from KC.
    3. Lance nematodes were in high numbers (~ 3k/100 cc soil) in Pythium infected roots submitted from SE MO.

    Last week saw the unfortunate arrival of a consistent enemy to bentgrass putting greens in Missouri.  Pythium root rot was diagnosed at two golf courses, one in Kansas City and the other in SW Missouri.  Both areas have been walloped with persistent rainfall, providing the pool (aka saturated putting green soil) which is the only thing this disease seems to require for infection.  Interestingly, in both of these cases, however significant root-knot (216 nemas/100 cc soil) and lance (~3,000 nemas/100 cc soil) nematode populations were detected in the samples.  Several prior research experiments have observed an increase in disease severity from a disease complex involving the combined forces of nematode infection and fungal or oomycete disease.  This makes complete sense, as the piercing of the root cortex by a nematode stylet presumably would be a prime infection court for a root disease. In the future, assessing nematode activity in the spring on greens consistently affected by Pythium root rot may be wise to detect and control this potentially predisposing factor.       

    Pythium spp. are not fungi, but instead are oomycetes and more closely related to diatoms and algae.  They persist in resistant structures called oospores, and spread through motile, flagellate spores called zoospores.  They cause a number of different, and distinct turfgrass diseases; most commonly on leaves = Pythium blight, while on roots = Pythium root dysfunction or Pythium root rot.  Pythium blight is common on Kentucky bluegrass, perennial ryegrass, and to a lesser extent on tall fescue lawns and creeping bentgrass fairways and tees.  On established bentgrass putting greens, Pythium blight is rarely seen.  Conversely, Pythium root rot is the most often diagnosed disease problem on bentgrass putting greens in the MU Turfgrass Disease Clinic. Pythium root dysfunction, as caused by Pythium volutum, is a disease most often observed on younger (<5-7 years) bentgrass putting greens that are well drained.  Roots are tan and lack root hairs, a symptom we have not observed here in Missouri.  In this region, superintendents most often mistakenly characterize their Pythium root issue as root dysfunction when in fact they have Pythium root rot.

    Last year, 35 courses had significant Pythium root rot as evidenced by severe necrosis, oospore presence and in some cases significant and observable zoospore activity (see this video).  Last week, I sent out a short survey to the superintendents who had a Pythium root rot diagnosis from the lab and inquired about watering and spring management practices.  Twenty-seven superintendents responded (thank you!), and upon first glance at the data there aren’t many common practices among the respondents.  One thing does stand out though - the amount of potentially root limiting products that are applied on greens in the spring.  Preemergent herbicides, DMI fungicides (ahem), and plant growth regulators are all applied in the crucial spring root growth period prior to the summer marathon.  While studies looking at these products alone show no appreciable decline in turfgrass quality or root density, perhaps adding a little water to all of them turns the cute Mogwai into a gremlin.  Research is needed, but the subject is considerable food for thought… except after midnight.     

    Field Day, Tuesday July 19th– Save the Date.

    Plans are underway for the 2016 Mizzou Turfgrass & Ornamental Field Day.  The event will be held July 19th at our research facility at South Farms.  Below are a few presentation topics to wet your whistle.  Registration for vendors and attendees will be available shortly.

    • Nitrogen source and application timing on large patch severity
    • Darnit, there’s dollar spot!  Rapid curative control options.
    • Spring dead spot management: Fraze, Fungicide, and Manganese?


    Lee Miller
    Follow on Twitter!  @muturfpath
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    Extension Turfgrass Pathologist
    University of Missouri