MU Field Day Research Booklet
Download at http://turf.missouri.edu/research/2019_Field_Day_Booklet.pdf
Thank you to all of those that came out and celebrated the diverse green industry research we had to offer at field day! From trees to weeds, to billbugs, diseases and bees, we covered quite a bit of ground. We appreciate all of the vendors, sponsors, and cooperators that helped us make the event possible, and all of the attendees that made it a success!
A special thanks also to all of our presenters, including those that put in double time to lead afternoon workshops. The tours given by Dave Trinklein, Josh McPherson CFM, and our program were very well attended. Hope to see some of those in our afternoon lawn care program again at our upcoming lawn care workshop series (more details and schedule coming soon).
August 1st Half Temps a Little Above Average
Except for a couple of lapses, (like today and yesterday), summer heat and humidity have been the rule over the last few weeks. So far in August, temperatures are approximately average to a little below average over much of the region. Expect temperatures to remain summer-like over the next week, so no break for summer stress and cool season turf disease activity quite yet.
Rainfall has been sporadic to start the month, with intense rainfall occurring just across the Missouri borders in eastern Kansas and western Illinois. Some areas in Missouri are actually drying out a bit, with tall fescue lawns going dormant in some locales. An intense system is slated to hit near Kansas City and NW MO tonight and tomorrow, resulting in high rainfall amounts and chances for localized flooding and high winds (see below). Rainfall chances for the eastern portion of the state rise next week in the longer range 6-10 day forecast.
Forecasted Rains on the Way
Summer Issues on Bent
Brown Patch - Disease of the Year
Last year anthracnose on bentgrass putting greens took the prize for disease of the year, and brown patch on tall fescue is vying for the crown in 2019. Buoyed by saturating rains in April and May and resultant high humidity, brown patch has ravaged lawns in the area. Now that we've made it to August and the glories of September are in our sights, what should the strategy be going forward?
Complaints of brown patch occurrence are still coming in from lawn care companies, homeowners, and other professional turfgrass managers that manage tall fescue in golf roughs, cemetaries, etc. In our research plots, some cool nights have reduced the severity of the disease considerably, and tall fescue has recovered from July outbreaks fairly well. If current symptoms are fairly new and not exceptionally severe, allocating resources now towards September aerification and overseeding may be a wiser investment. This does come at a risk of more bermudagrass encroachment into brown patch affected lawns, so if you have that risk you may choose to continue brown patch control measures to stave off bermuda competition.
Brown Patch vs. Gray Leaf Spot
Another confounding issue over the last several years has been the sporadic arrival of gray leaf spot on the Missouri scene, particularly in St. Louis, Columbia, and Springfield. August and early September is the time to scout and be aware of the potential for gray leaf spot, and not misdiagnose it as brown patch. Invest in a 10x hand lens, and closely examine areas around the margins of tall fescue decline. Brown patch should occur mainly in patches in the stand, and newly infected leaves should have a lesion with a brown margin and light tan interior. Conversely, gray leaf spot may occur spotty in the landscape, or in extremely intense cases as a widespread blight. Newly infected leaves will have distinct spots for lesions that have a grayish interior (no kidding) and a very dark, nearly black margin. Spots can coalesce to run across the leaf blade, but will be more curved than brown patch lesions.
The kicker with gray leaf spot is that control relies on thiophanate methyl and not azoxystrobin as with brown patch. The longest and most effective control is a tank-mix of thiophanate methyl and azoxystrobin. The second kicker is that gray leaf spot likes to dine on seedlings, so tall fescue that is planted a little too early in late August or in a warm September (which unfortunately happens) is especially susceptible. A third problem is the gray leaf spot pathogen sporulates heavily and therefore can move quickly. Monitor for the disease aggressively, and don't overwater and spread spores needlessly.
At this point, gray leaf spot in Missouri is not a perennial occurrence and therefore preventive thiophanate methyl applications in all, but very high amenity tall fescue areas with a history of the disease, are not warranted. As stated above though, monitoring and early detection is crucial, so if in doubt sending a sample into a diagnostic lab isn't a bad move.
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Extension Turfgrass Pathologist
University of Missouri