GOLF: Do you increase nitrogen fertility on greens when lower temperatures occur during summer months?

No - Stick with normal spoon feeding
Yes - Add a little (<0.05 lb N)
Yes - Add medium amount (~ 0.05 - 0.1 lb N/week)
Yes - Add a lot (~ 0.1 lb N/week or more)

Update (8/21/2020)


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Cool Start to August

  1. August has given a much given break to cool-season turfgrass. – MU Climate Center
  2. Appears cool August temperatures may be over next week. – NOAA

The blues may be gone for a while, which ironically can make turfgrass managers in summer sad. A cool start to August produced temperatures 2-3 degrees below normal for the month in much of the region. Lows in the low 60s or even high 50s gave cool-season turfgrasses a much needed break and provided some natural fungicide for diseases like brown patch and Pythium. Some superintendents even used the break as an opportunity to aerify putting greens, and some fertilizer and even seed was put down on some lawns. This break unfortunately seems over, as a return to summertime temperatures are expected next week. Fall forecasts indicate a warmer than normal pattern for much of the U.S., hopefully not as hot as last year which had September highs consistently in the 90s. (click here to view last year's report). On the bright side, we are in the back half of August and day length is getting shorter, (over an hour shorter than mid-June) so stress periods will be shorter.

The cool air mass colliding with hot summer air produced considerable instability and heavy rainfall events for the middle and northern portions of the state. A terrible derecho event devastated Iowa with 100+ mph winds, wrecking over 10 million acres of crops and leaving many homeless and without power. In St. Louis, 5-7 inch downpours produced heavy flooding and severe localized damage to turfgrass facilities. Both urban centers of KC and STL are 3-5" above normal precipitation over the last 30 days, producing an "owl eye" appearance to the precipitation map ( Southwest Missouri has had significantly less rainfall, at 1-2" below normal. Into next week, little to no rainfall is expected in the region which will be a blessing for those involved in rebuilding efforts.

Heavy Rains for STL

  1. Five+ inches of rain already in August for many areas along I-70. – NOAA
  2. Dry down expected through next week. – NOAA

Quick Hits

    Keep an Eye Out for Gray Leaf Spot on Tall Fescue

    1. Gray leaf spot damage will appear random, and not aggregated in large patches.
    2. Dark black margins and grayish interiors differentiate GLS symptoms.

  • Gray Leaf Spot on Tall Fescue Warning – As indicated in the last report, we are starting to see a few symptoms on our research farm of this disease, but have no reports yet of widespread outbreaks. Keep an eye out for smaller, more random areas of tall fescue decline that have lesions with darker, black margins than brown patch symptoms.

  • Summer Patch keeps rolling in

    1. Bentgrass on the left.
    2. Kentucky bluegrass on the right.

  • Summer Patch on Kentucky bluegrass & creeping bentgrass – Several samples with severe summer patch on both Kentucky bluegrass sports fields and creeping bentgrass putting greens have come into the lab over the last 10 days. Heavy rains may have washed away prevention, and at this time of the season any small straw can break the back of a stressed-out root system. As mentioned last week, a watered-in application of one of the "cool" DMIs tankmixed with a QoI in the form of Briskway and Navicon should help shut the disease down and start recovery. Frustratingly, however, these fungicides are not labeled for high amenity sports turf surfaces and only on golf courses. Sports fields are left with Headway, Pillar or other choices with older DMI chemistries that in the heat of summer can adversely regulate growth (on field which may also be on PGRs). I can't see the distinction between a sand-based sports field with Kentucky bluegrass mowed to 0.5" or less that needs to be shown to fans on the tele vs. a 100-acre golf course facility. The technology should be available for these professional sports facilities separately from other recreational, park or school facilities that children would play on.

  • Anthracnose hits bentgrass in cool down.

    1. Blotchy type symptoms that can impact particular segregate bentgrass clones.
    2. Darkened basal anthracnose rot symptom on bentgrass.

  • Anthracnose – Basal rot anthracnose on bentgrass putting greens has also started showing up in the lab over the last week. Remember that this disease is associated with low nitrogen and a stressed-out plant. Putting greens are at their lowest point in August, and the cooler temperatures don't magically erase the ills of June and July. As the bentgrass strives to get back on its feet with increased growth potential from cooler temperatures, the root system is still limited in function and can't take up nutrients like nitrogen as well as it needs to. Add in a huge flush of nutrients from big rain events and the soil profile cupboard may also be bare. Enter anthracnose, strolling nonchalantly down the leaf sheath and into the crown of a stressed, nitrogen-starved plant. If struggling with basal rot anthracnose on bent, consider flowing with temperature swings in your spoon-feeding program and putting a small, extra bite of chicken on the plate when conditions are conducive for growth.

  • The Yin and Yang of Soil Moisture

    1. Black layer is caused by the yin of too much soil moisture.
    2. Localized dry spot caused by the yang of water repellancy.

  • Black Layer vs. LDS – It's an odd day when in two successive samples I encounter two such wildly different maladies. Last Thursday, I opened a package with the yin (the dark side) of too much moisture and foul-smelling back layer, and followed it with a box containing the yang (the light side) of a hydrophobic soil profile with localized dry spot (LDS). Both of these will show up on a TDR, but I also suggest using the old school method of soil profile examination. With a cup cutter, soil profiler or soil core sampler, black layer should be readily apparent and smelled, but in some cases the cup cutter may need to be split open to expose the full gore. For LDS, use an eye dropper to place water droplets on the exposed flat soil core from a soil profiler or split open cup cutter plug. The droplets in the above photo stayed there for two hours. Black layer? Vent. Check drainage. Move away from sulfur and ammonium sulfate applications until fall. LDS? Vent. Consider a full rate wetting agent application with a full amount of post-application irrigation.

Spruce up Swards in SSSSeptember


  1. Spread Seed…
  2. In September with Sustenance

As we enter into the final portions of summer and into fall, many homeowners and turfgrass managers may be looking at lawns and other cool season turfgrass areas with a bit of angst and a "come on, really?" attitude. After a season of stress, August is the month cool season grass is at its worst - ratty and subject to diseases and weed infestation. This being said, fall is on the horizon and applying a bit of rejuvenation crème at the right time do wonders for our lawn's appearance.

In this vein, SSSS is an acronym that could suit September, standing for "Spread Seed in September with Sustenance". Since it's wise to check acronyms these days, my search finds the quadruple S only stands for "Secondary Security Screening Selection", which at most is inconvenient and not incendiary. If you double up to "Ssssssss", however, a 1973 horror film claims the title, and after watching the brief trailer I suggest anyone with ophidiophobia to skip this one.

The quality of lawns lies in the number of turfgrass plants creating a uniform dense turfgrass sward. Therefore, providing a stressed out or declined lawn with a solid September overseeding is a sound and perhaps most effective method of rebuilding quality. Many homeowners have this unrealistic expectation that an established lawn will persist into infinity, while at the same time trading out every other plant in their landscape, including trees on occasion. In the wildly swinging climate of the Missouri transition zone, the expectation is perhaps farthest from reality. Also remember that our most robustly used species, tall fescue, is a bunch type plant with no stolons and no rhizomes to creep into bare spaces. Last but not least, seed is organic!

Overseeding tall fescue at 4-5 lbs of pure live seed (PLS) per 1,000 sq ft is a solid route to recuperation. At this time of year, my suggestion for brown patch damaged areas or other thinned areas is to consider putting the effort into this arena rather than into pesticide applications. Along with this, a full pound of N per 1,000 sq ft is also suggested in September. Other nutrients and potential pH manipulation should be applied based on a soil test, and right now is a good time to assess those needs. A core aerification or power-raking (if not done in a last few years) is a great way to start the whole process, but these practices shouldn't be a prerequisite or impediment to overseeding efforts.

One fly in the ointment could be weed control. Crabgrass has been prevalent this late summer, and in some instances has even broken past spring preemergent applications. With frequent rainfall events, nutsedge with its proclivity for wet feet has also been troublesome this year. Selective herbicides such as quinclorac for crabgrass control or topramezone for bermudagrass suppression carry little to no restriction for application prior to seeding. Halosulfuron or sulfentrazone targeting nutsedge, however, requires four weeks between application and seeding. Read the labels carefully and if in doubt consider spot applications of a non-selective herbicide such as glyphosate 2-3 days prior to seeding.

Last but not least, remember to measure your area prior to seeding, fertilization or any application of product, and calibrate accordingly. As one of his last contributions in an illustrious career, Dr. Brad Fresenburg constructed a lawn fertilizer calculator web application - While geared towards the homeowner, lawn care operations or any turfgrass manager may find this useful for assessing the area of several properties with the google maps calculator and utilizing the easy to use interface to determine fertilizer needs. As an added trick, if you add the seed germination % in as one of the nutrients the amount of pure live seed needed for an area can also be easily calculated.

Lee Miller

Extension Turfgrass Pathologist
University of Missouri
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