Plans are ramping up for the 2019 Mizzou Turfgrass & Landscape Field Day to be held on Tuesday, July 30th at South Farms in Columbia, MO. The full schedule is complete, and with the new alternate year schedule includes a ton of great informational presentations. We have got preapproval for a large amount of CEUs from the GCSAA and ISA. Much better to obtain these credits outside in the fresh air rather than in a stuffy classroom!
The full field day schedule (and it is full!) can be found at http://www.mufieldday.com/schedule.html along with all the information regarding the event.
Attendees, sponsors and exhibitors can all register by visiting https://extension2.missouri.edu/events/2019-mizzou-turfgrass-and-landscape-field-day.
Mild June looks to finally give way to summer
Almost through June, past the summer solstice and the days are getting shorter. Normally the region gets at least a hearty slice or two of summer's heat prior to the solstice, but not this year. Below is some data from Columbia, MO on the high and low temps up to June 26th of each year since 2012. Particularly on bentgrass putting greens and to some extent on tall fescue/Kentucky bluegrass, a day with significant summer stress and higher potential of summer disease symptom development might be estimated with high temperatures at or above 90 F and/or low temperatures at or above 70 F. Looking back seven years, only 2014 mirrors the type of spring and nearly first month of summer we've experienced this year in Missouri. Additionally, in summers following the 20 wettest Mays in Missouri, 4 were above average, 9 were near average (± 1 degree), and 7 were below average. Wow, optimism from a turfgrass pathologist?! Not quite. The heat that's here today is forecasted to stay. A change towards summer-like, above normal temperatures is forecasted to end June and start July. Combined with saturated soils and resultant high humidity, an increase in disease severity should be expected.
Very Cool Start to Summer
Columbia, MO - # of days w/max temps ≥ 90 and mins ≥ 70. – MO Ag Weather Database
As noted in the previous report, rainfall in May set a precedent (see Dr. Pat Guinan's report to read the historic context of May 2019 storms). June has followed suit thus far with much of the state 1 - 3" of above normal. While the rest of this week is forecasted to remain dry, an unsettled pattern is forecasted in the first week of July. Rainfall in summers following the 20 wettest Mays in Missouri has historically resulted in 7 above average, 11 near average (± 1 inch), and 2 below average normal rainfall.
Spotty rain in June
Wet Weather Issues on Putting Greens
Pythium Root Rot and Lance Nematodes
Brown Patch Striking Swiftly
An unfortunate play on the UPS slogan and perhaps the worst title in all of these reports attempts to highlight the quick and profound emergence of brown patch in the area. Several reports from homeowners and lawn care operators reflect the fickle nature of beautiful green tall fescue that can quickly slide into the grips of this disease. We also have aesthetically pleasing (only to a pathologist) brown patch smoke rings on creeping bentgrass greens starting to flare in our research trials.
Brown patch is caused by Rhizoctonia solani, which is the junk heap of pathogen taxonomy. A number of different pathogens share this name and cause different diseases on different hosts. Think of a baseball game where all the players wear the same uniform. This being said, brown patch on cool season turfgrasses such as tall fescue, Kentucky bluegrass and creeping bentgrass is caused by this extremely ubiquitous pathogen. If a conducive environment is present (i.e. heat, high humidity, shade, leaf wetness) disease symptoms are likely to occur.
The focus of this article is lawn care and tall fescue, but those in sports turf or use Kentucky bluegrass do not forget that some cultivars, (in my experience 'HGT'), can also have issues with brown patch. With this weather pattern, I would expect to see brown patch on these areas as well.
As written in previous reports, (see this July 2015 report), consumer grade fungicides which contain the active ingredients thiophanate-methyl, propiconazole, myclobutanil, etc. do not provide adequate control of this disease on tall fescue even when applied according to label directions. Flutolanil and fungicides in the strobilurin class (specifically azoxystrobin) historically provide the best control of brown patch in tall fescue, but both (while not restricted use) are not marketed or widely available for the homeowner. (Update: A new product "Scotts DiseaseEX" does contain azoxystrobin, and can be found in commercial stores. More on this development in future reports.) Therefore, in most instances, a professional, certified applicator is recommended to acquire and apply these fungicides.
The question about organic control often comes up. The smarteleck answer a chemist might give is that fungicides are all organic since they contain a carbon molecule, but the response is not recommended. The correct answer is that at this time a viable, effective alternative to controlling brown patch (and many other diseases for that matter) is not available.
This leaves our cultural practices for management if fungicides aren't employed. Humidity and free water on the leaf blade are the enemy and should be curtailed if at all possible. Below is a small list.
1. Prune trees (not aggressively and later in the fall) to remove shade.
2. Those with in-ground irrigation systems a) shouldn't be using them now and b) when they do use them should schedule for early morning. Removal of dew and guttation fluid with irrigation at dawn is much better than initiating the leaf wetness period at dusk.
3. Mow tall fescue to the correct height. At least 3 inches and preferably 4. A higher canopy can cause more humidity, but in the long run the reduction of stress on the plant will win the day.
4. Again why not overseed damaged areas in the fall with more tall fescue? Lawn quality is all about the density of the grass. The weeds do it, why not us?
5. Last but not least, nitrogen management. In a year like this, nitrogen may have run out of the system even if it was applied in April. Some current research suggests a spoonfeeding approach on lawns (0.25 - 0.5 lb N/month) may not increase brown patch. Most DIY homeowners, however, may lay a full pound on which is still not recommended.
Lawn Care Workshop at Field Day: Last but not least, we have initiated a field experiment regarding nitrogen impacts on brown patch and gray leaf spot severity (see the fourth photo in the panel above). We are finishing up inoculation procedures this week and hope to demonstrate brown patch and hopefully gray leaf spot infection. This along with sprayer calibration and discussion of our newly installed 132 cultivar NTEP tall fescue trial will be the focal point of a 1-2 hour workshop aimed specifically at lawn care after lunch at our upcoming field day on July 30. We hope you will take this opportunity to visit and learn with us about tall fescue management and disease control.
Follow on Twitter! @muturfpath
Like on Facebook! Mizzou Turfgrass
Extension Turfgrass Pathologist
University of Missouri