Summertime! Deep Roots, Brown Patch, Flatsedge?, Divot Study Ends

CDGATurfgrassProgram
7 min readAug 4, 2023

Summertime! One word describes a glorious week just experienced. The game of golf saw a solid week of summer — warmth both day (90s) and night (70s). Importantly, it followed all the weather seen by the landscape — turf, ornamentals, trees — up to now. A few bumps in the road, as usual, but overall some (me) are beginning to say this one (growing season 2023) has been a good one. Primarily because extended periods of extreme heat were not experienced in our region. It now gives August an opportunity to bring optimal playing conditions across the board. And it has already. One only has to take a step on surfaces from tees, to fairways, to greens. Then smile.

Image 1. Early one morning at the 121st Western Amateur, July 31-August 5, 2023. North Shore Country Club, Glenview, IL. Settle, Jul 31, 2023

And roughs! Kentucky bluegrass roughs are also looking terrific. So, let’s get to the “root” of all these early August observations. Yep, we have been able to retain a majority of our cool season turfgrass roots (stored energy) so far. Something we do not always experience. For sure it did not happen during a string of summers not too long ago. In 2010 it flooded in late July. In 2011 it flooded in late July. And in 2012 it was all about extreme summer heat (we counted something like 40 days of 90+ highs). Back to summer 2023. For superintendents and staff preparing for daily fee, a club championship, or a major event like the 121st Western Amateur, this August is now about as good as it gets — turfgrass conditions that is. So get out, enjoy and experience an environment that will make you smile.

Weather

Figure 1. Current air and soil temperatures as we begin August. Bob Berry Sunshine Course, Lemont, IL
Figure 2. July weather recap. “Chicago Midway Airport received 11.28” of rainfall in July 2023, the wettest July since 1928 at Midway. Courtesy National Weather Service, Chicago, IL

Measuring Roots

The end of July is a good time to stop and measure roots because it usually has followed some of the harshest conditions of summer = the month of July. What we found in a nursery green study at North Shore Country Club is interesting. It is telling us that creeping bentgrass has retained a majority of the roots it amassed during the spring season.

Missing Root Decline in Summer 2023

It means the usual physiological decline caused by supraoptimal soil temperatures has been missing in 2023. Also largely missing have been various fungal root rots — Pythium root rot can be a common issue of creeping bentgrass greens.

Image 1. Shehbaz Singh measures maximum root length of four cores from an untreated check plot in a L-93 plus SR1119 creeping bentgrass green. The core is then cut to a 2 inch length and this is then used for nematode extraction (this site has a history of root knot, lance and ring nematodes). Low numbers of root-feeding nematodes were found. Settle, Jul 31, 2023
Figure 1. Fungicides for Additional Plant Health Effects. Fungicides were applied on a 14 day interval, then immediately watered in to the depth of roots. By the end of July three applications had been made and maximum root length was measured from an L-93 plus SR1119 creeping bentgrass nursery green. Root data represents an average of 4 1/2" diameter cores taken from each 4 ft x 6 ft plot. Study design is a randomized complete block with 4 replications. Means with the same letter are not significantly different. North Shore Country Club, Glenview, IL, Jul 31, 2023

Brown Patch, Rhizoctonia solani

Over a two week period conditions for brown patch have been met from time to time. What does that look like? Well, all the action is at night.

Conditions Required

  1. Warm nights (lows very close to 70 degrees).
  2. A long period of leaf wetness (minimum duration of at least 10 hours).

Rhizoctonia is a ubiquitous fungus in our soils. Their activity can be helpful in the degradation of organic matter that otherwise can build up. But some are also plant pathogens. For example, most cool season turfgrasses are highly susceptible to damage by R. solani during hot, humid summer periods. Unfortunately many turfgrasses used extensively for golf’s playing surfaces are highly susceptible. This is where one species, Kentucky bluegrass, has an advantage when it comes to a fungal disease known as brown patch.

Resistant to Brown Patch

  • Kentucky bluegrass, Poa pratensis L.

Moderately Resistant to Brown Patch

  • Creeping Bentgrass, Agrostis stolonifera L.

Highly Susceptible to Brown Patch

  • Perennial Ryegrass, Lolium perenne L.
  • Tall Fescue, Festuca arundiaceae Shreb.
  • Annual Bluegrass, Poa annua L.

Recent Research

Previous recommendations were centered around nitrogen fertility. Too much N was always thought to exacerbate brown patch. Recent research at Purdue by Cale Bigelow and Jada Powlen has shown that nitrogen maybe wasn’t such a bad guy after all. They looked at alternatives to fungicides and found that use of surfactants (to reduce leaf wetness duration) could also provide a level of brown patch suppression.

When evaluating the various interactions of cultivar, N rate, and surfactant compared to a granular fungicide, the greatest impact was achieved when planting a resistant cultivar, reducing disease severity by 68%.

Best of all, the research was able to show that there was one sure-fire way to reduce brown patch. Plant a NEWER VARIETY of tall fescue. Why? Well, they were specifically selected for resistance to brown patch. If you are keeping score: Tall Fescue Breeders 1 vs Brown Patch 0 = it’s a win!

Image 1. Brown patch symptoms on a RTF tall fescue tee at Bob Berry Sunshine Course, Lemont, IL. Settle, Aug 3, 2023
Image 2. Brown patch is a common disease at midsummer. Damage is usually limited to thin patches that are circular and will slowly continue to expand over time if conditions (warm, humid nights) are conducive. Bob Berry Sunshine Course, Lemont, IL. Settle, Aug 3, 2023

References

An Integrated Cultural Management Approach for Brown Patch Disease Suppression in Tall Fescue Lawns by Jada Sue Powlen, PhD

2022 Brown Patch Ratings of Tall Fescue Cultivars at West Lafayette, IN

2018 National Tall Fescue Test (2022 Data Progress Report NTEP №23–7)

Flatsedge, Cyperus sp.

It isn’t very often that you will find a weed that is able to out compete healthy creeping bentgrass. But that is exactly what I saw this week at a golf course.

The superintendent wrote an email to describe the problem. “I did call you this afternoon concerning weed identification and possible remedies for this situation. Attached is a photo showing the weed/grass. No matter what it ends up being, it loves wet areas around irrigation heads and areas of high water tables (springs). If you need a sample or would like to see it in person, I could either bring you a sample or you could come out to see it in its environment.

The weed turned out to not be a grass (Poaceae family). Instead it was actually quite different (Cyperaceae family). I quickly was able to determine it was a sedge, but which one? Actual identification as a flatsedge was done by sending photos to a sedge expert, Dr. Matt Elmore, Rutgers University. It was a flatsedge. Thank you Dr. Elmore!

This was good news for the golf course superintendent because it makes selective control that much easier. A couple families of herbicides exist which can safely remove sedges from grasses. So in this case, a flatsedge will be removed without harming a Penncross creeping bentgrass fairway.

Identification — “Sedges have edges.”

There is one simple way to ID sedges. You just need to investigate a stem with a thumb and finger. Sedges have triangular-shaped, solid stems.

Image 1. A grassy-looking weed infesting a creeping bentgrass fairway at a Chicago golf course. Settle, Aug 3, 2023
Image 2. A sample is taken for identification. It is found to be a sedge. Settle, Aug 3, 2023
Image 3. The flowering seedhead is a very important aspect when trying to identify a weed. In this case a sedge in the Cyperacea family. Settle, Aug 3, 2023

References

The Significance of Cyperaceae as Weeds — USDA ARS. by Charles T. Bryson and Richard Carter

Identifying and Understanding False-Green Kyllinga in Cool-Season Turf. Rutgers, Matthew Elmore and James A. Murphy

Sedge Control for Turfgrass Professionals Purdue, Aaron Patton

Final Investigation of Divot Study — August 4, 2023 by Shehbaz Singh, MS

Data collection for the fall divot trial was halted on Dec 7, 2022. Turfgrass was dormant. However, certain divot treatments were still unacceptable. In early March data collection once again began for the two tees (a Piranah creeping bentgrass and a HGT Kentucky bluegrass tee) used for divot repair research on Bob Berry Sunshine Course, Lemont, IL.

Creeping Bentgrass Trial: Fall 2023 Divot Results

Divots were made on Sep 7, 2022 for the fall treatments. Divot mixes without seed were not acceptable because divots did not recover to at least 50% during a 14-week (~3 month) time period. In contrast, divot mixes with seed were able to provide acceptable recovery of divots during the same 14-week period (on or before Dec 7, 2022).

Image 1. Shehbaz Singh takes Normalized Difference Vegetation Index readings on a tee. It electronically measures turf canopy reflectance of red and near infrared wavelengths. NDVI is a measurement that can be used determine turfgrass quality, Bob Berry Sunshine Course, Lemont, IL. Settle, Aug 3, 2023

8 Months of Recovery

On May 4, after almost 8 months following fall divots, divot mix treatments with seed were showing 80% or more divot recovery.

10 Months of Recovery

On July 6, 2023, all divot mixes without seed showed at least 50% recovery.

11 Months of Recovery

On Aug 3, 2023, all divot mixes without seed the Piranha creeping bentgrass tee had finally reached 80% or more of recovery.

Figure 1. Monitoring Fall 2022 Divot Recovery: Comparison of divot recovery in a Piranha creeping bentgrass tee using a sand divot mix with and without seed. Bob Berry Sunshine Course, Lemont, IL
Figure 2. Monitoring Fall 2022 Divot Recovery: Comparison of divot recovery in a Piranha creeping bentgrass tee using a compost divot mix with and without seed. Bob Berry Sunshine Course, Lemont, IL
Figure 3. Monitoring Fall 2022 Divot Recovery: Comparison of divot recovery in a Piranha creeping bentgrass tee using a 8–1–1 (sand-compost-soil) divot mix with and without seed. Bob Berry Sunshine Course, Lemont, IL
Figure 4. Weeks to 50% recovery for divots made in the spring, summer, and fall during 2022 on a Piranha creeping bentgrass tee. In the fall, divot mixes without seed took from 41 to 43 weeks to recover (turfgrass recovery took until summer, 2023). It clearly shows that divot mixes in the fall must use seed.

Final Photo

Two front yards in Chicago. One is a Kentucky bluegrass lawn (left) and another (center) is a wonder of flowers and foliage. Settle, Jul 31, 2023

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CDGATurfgrassProgram

Written by Derek Settle, PhD & Shehbaz Singh, MS. Mission: Provide science-based turfgrass research and diagnostics to 400+ member golf courses/superintendents.