Backward Spring Goes! Cold, April Showers, Yellow Patch and Tenacity Research

CDGATurfgrassProgram
7 min readApr 5, 2024

April showers bring May flowers? Maybe so, but in a week we actually saw periods of snowfall too. Because why not? The upper Midwest was once again adjusting to temperatures in the 30s for lows and backwards spring goes. After an early warm up in March, spring 2024 seems to be experiencing a hard reset — it’s like that little, hard-to-find, recessed red button was pressed by Mother Nature. Don’t worry, spring will be back next week with predictions of daytime highs in the 60s for northern Illinois.

Image 1. An example of a healthy Poa/bentgrass green with mixed collar of Kentucky bluegrass/creeping bentgrass/annual bluegrass collar as of the first week of April in Chicago. Note: A majority of this green is light green in color and means levels of Poa annua are greater than creeping bentgrass. Apr 1, 2024, Settle

Given it was a week filled with more cool, wet days than not it wasn’t surprising that first diagnostic visits occurred. The issue? A lesser known Rhizoctonia disease was causing patch symptoms on young creeping bentgrass golf greens. Meanwhile, spring 2024 continues to deliver interesting news! Here’s a few: 1) The Masters is next week and spring is in the air at Augusta National Golf Course in Augusta, Georgia. 2) Periodical cicadas in Illinois are compared to rock stars, and 3) A total solar eclipse is about to happen on April 8th, which means the moon’s shadow will darken that day. Spring 2024 already feels, looks, and sounds different. So hang on.

Weather

Figure 1. April Chills: In a week average soil temperatures at a 2" depth lost ground. It meant spring took a pause in April’s 1st week. Bob Berry Sunshine Course, Lemont, IL.
Figure 2. 48 hour rainfall totals show Chicago did not receive an excessive amount of precipitation (rain + snow). A majority of the suburbs saw less than 0.5 inches (blue colors). Courtesy USGS, Apr 4, 2024
Figure 3. Snow?!? Actually, snow in April is not uncommon for Chicago. It is normal to see an average of 1.3 inches, but recent years have seen more. Both 2003 and 2007 saw 3 inches, 2018 saw 3.2 inches, 2020 saw 4.7 inches and 2019 saw 7.9 inches. The year 1938 is the grand champion at 13.6 inches. Data is from 1885–2022. Chicago snow total data courtesy NOAA

Scouting for Diseases on Greens — Yellow Patch, Rhizoctonia cerealis

One of the first diseases that can negatively impact greens is caused by a soilborne fungus that can thin turfgrass in patches. It is known as yellow patch or Rhizoctonia cerealis. It is also known as low-temperature brown patch. It is active during cool, wet periods of the early spring.

Image 1. Yellow patch, Rhizoctonia cerealis, negatively impacting a brand new 007 creeping bentgrass green (>1 year old). Note: In bentgrass, yellow patch disease actually appears as a reddish-bronze colored patches. The common name yellow patch is descriptive of what happens to Poa annua greens. Settle, Apr 1, 2024
Image 2. Using a cup cutter to obtain a diagnostics sample, the superintendent takes a sample on the edge of a patch with both healthy and diseased turfgrass present. Settle, Apr 1, 2024
Image 3. Incubation of the sample can be necessary to aid diagnosis. Settle, Apr 2, 2024
Image 4. Large mycelium with right angle branching is indicative of Rhizoctonia fungi. Settle, Apr 1, 2024

Conditions

Air temperatures of 50–65 F with long periods of leaf wetness.

New Bent Greens Susceptible

In Chicago, yellow patch can be problematic on newly seeded creeping bentgrass greens. This fact was true in both cases observed this week. Also, and probably important, the bentgrass greens were new USGA-spec root zones seeded in 2023. A lack of beneficial/competing microorganisms in a new root zone may explain why brand new greens are more susceptible.

Control

This is not a disease that causes a lot of damage. Thankfully, the blight is limited to older leaf blades and the youngest, growing point remains green and intact. Also,the plant crown survives. And so one option is to do nothing and affected allow plants to naturally grow out and recover as conditions warm. Rhizoctonia cerealis is not active at warm temperatures.

  • Nitrogen. Adequate N fertility in the fall is recommended, this is to help spring growth (slow/lagging growth will inhibit turfgrass recovery).
  • Fungicides. A limited amount of research has been conducted on yellow patch. In part, that’s because it is a minor disease that appears in the early spring. Many groups of fungicides offer control (QoI, SDHI, DMI).

Research-based Fungicides for Yellow Patch Control

Chemical Control of Turfgrass Diseases 2020, 26. Yellow Patch (page 31)

Scouting for Broadleaf Weeds on Greens? — Yes, some can establish on daily-mowed greens

A scouting superintendent on Chicago’s south suburbs identified mouse-ear chickweed competing with creeping bentgrass on a green. It’s another sign that things are warming since winter. Certain perennial broadleaf weeds have now begun to resume their growth.

Mouse-ear Chickweed, Cerastium vulgatum

Dr. Aaron Patton, Purdue University, has excellent fact sheets on weeds.

Identification

“Similar to common chickweed, its prostrate growth habit and capabilities to withstand low mowing practices make mouse-ear chickweed a prominent weed in turfgrass and other mowed areas throughout the United States.”

Image 1. Identification: Mouse-ear chickweed in a creeping bentgrass green. Chicago GCS, Apr 4, 2024

Tenacity Herbicide for Selective Removal of Creeping Bentgrass from Kentucky Bluegrass by Shehbaz Singh, MS

In 2023, a herbicide study sponsored by Syngenta was conducted on tees A, B and C at Bob Berry Sunshine Course in Lemont, IL. Results from tee A will be discussed below.

Image 1. Tee A was regrassed to ‘HD Sports 2.0’ Kentucky bluegrass, but had previously been creeping bentgrass and quickly recontaminated the surface. This tee served as one of three study sites which explored using Tenacity to selectively remove creeping bentgrass contamination in tees at Bob Berry Sunshine Course, Lemont, IL. Settle, Mar 26, 2024
Image 2. Two or three applications of Tenacity successfully allowed us to selectively control creeping bentgrass and this allowed regrowth of ‘HD Sports 2.0’ Kentucky bluegrass. Untreated 5 ft x 10 fyplots can be clearly seen (lighter green color), Bob Berry Sunshine Course, Lemont, IL. Settle, Mar 26, 2024
Image 3. Photos of 5 ft x 10 experimental plots of untreated, Tenacity 5 fl oz/A applied twice, and Tenacity 5 fl oz/A applied three times. Darker green color indicates regrowth by ‘HD Sports 2.0’ Kentucky bluegrass. Bob Berry Sunshine course, Lemont, IL. Singh, Apr 2, 2024

Tee A Background

Tee A was originally grassed to ‘Penncross’ creeping bentgrass (2004–2020). In 2020 the Wadsworth Golf Construction Company provided a extensive renovation of Bob Berry Sunshine Course. Creeping bentgrass on Tee A was killed using glyphosate. The dead bentgrass surface was cut by a sod cutter and then removed. Tee A was reseeded with ‘HD Sports 2.0’ Kentucky bluegrass. However, a 2022 evaluation of all tee surfaces at the course revealed up to 80% contamination of creeping bentgrass on Tee A. Within 3 years of renovation, creeping bentgrass found its way back and had aggressively contaminated the bluegrass tee surface.

Objectives:

  • Evaluate selecive creeping bentgrass removal
  • Evaluate Kentucky bluegrass regrowth
  • Evaluate turf quality both visually (1–9 scale) and electronically by Normalized Difference Vegetation Index (NDVI)
  • Evaluate 2 versus 3 applications
  • Evaluate any phytotoxicity

Material & Methods

The study was conducted using a randomized complete block design.

  • A total of 3 treatments
  • A total of 4 replications
  • Individual plot size = 5 ft x 10 ft

Treatment Description

Treatments were sprayed using CO2 backpack sprayer operated at 40 psi; three nozzles with XR TEEJET 800VS. Applied in water equivalent to 2 gal per 100 sq ft. A total of 2 or 3 applications were made. Tenacity was mixed with a non-ionic surfactant (NIS) at the rate of 0.25 % by volume.

To promote regrowth of Kentucky bluegrass, liquid urea was applied six times at a rate of 0.5 lbs N/1000 sq ft bi-weekly following the second application date on Sep 12, 19, 26, and Oct 3, 10, 17 in 2023.

Data

  • Visual Quality (1–9 scale, with 6 = minimum acceptable and 9 = best)
  • Normalized Difference Vegetation Index (NDVI) using GreenSeeker/Trimble HCS-100
  • Creeping Bentgrass (% per plot)
  • Kentucky Bluegrass (% per plot)
  • Brown Turfgrass (% per plot)
  • Phytotoxicity (% per plot)

Creeping Bentgrass Contamination

At study start, the average contamination by creeping bentgrass in experimental plots was 78.8%. Three months later, bentgrass had been significantly reduced by Tenacity. For example, two applications 14 days apart had resulted in 8.8% creeping bentgrass and three applications 14 days apart had resulted in 11.3% creeping bentgrass.

After 6 months, creeping bentgrass in tee A was reduced to 5% and 1.75% for 2 and 3 apps respectively. The untreated plots remained unchanged with creeping bentgrass contamination levels still at 78.8%.

Figure 1. Creeping bentgrass (%) given 2 or 3 Tenacity applications on a ‘HD Sport 2.0’ Kentucky bluegrass tee. Applications in 2023 were Aug 22 and Sep 6, 2022 (2 apps.) plus Sep 19 (3 apps.). Two applications (blue box) were as good as three applications. Fisher’s LSD (P<0.05). Bob Berry Sunshine Course, Lemont, IL

Kentucky Bluegrass Re-growth

At study start, the average amount of Kentucky bluegrass in experimental plots was 21.3%. Three months later, bluegrass had significantly increased by Tenacity’s removal of creeping bentgrass. For example, two applications 14 days apart had resulted in 91.3% Kentucky bluegrass and three applications 14 days apart had resulted in 90.0% Kentucky bluegrass.

After 6 months, Kentucky bluegrass in tee A had increased to 88.8% and 88.5% for 2 and 3 apps respectively. The untreated plots remained with low levels of Kentucky bluegrass (21.3%).

Figure 2. Kentucky bluegrass re-growth (%) given 2 or 3 Tenacity applications on a ‘HD Sport 2.0’ Kentucky bluegrass tee. Applications in 2023 were Aug 22 and Sep 6, 2022 (2 apps.) plus Sep 19 (3 apps.). Two applications (blue box) were as good as three applications. Fisher’s LSD (P<0.05). Bob Berry Sunshine Course, Lemont, IL

Visual Turf Quality

Average turf quality of 5.5 was recorded at study start for all treatment plots. Minimum acceptable turf quality (6.0) was observed for treated plots at both 3 months and 6 months after first Tenacity application. A significant increase in Kentucky bluegrass population and supplemental nitrogen fertilization helped treated plots attain acceptable visual turf quality.

Note: Visual quality of treated plots initially fell significantly due to the selective removal and browning of creeping bentgrass in patches (data not presented).

Figure 3. Visual quality (1–9) given 2 or 3 Tenacity applications on a ‘HD Sport 2.0’ Kentucky bluegrass tee. Applications in 2023 were Aug 22 and Sep 6, 2022 (2 apps.) plus Sep 19 (3 apps.). Two applications (blue box) were as good as three applications. Fisher’s LSD (P<0.05). Bob Berry Sunshine Course, Lemont, IL

Normalized Difference Vegetation Index (NDVI)

Average NDVI of 0.700 was recorded at study start for all treatment plots. An average NDVI of 0.827 was recorded at 3 months and 0.810 after 6 months after first treatment application. Both increased Kentucky bluegrass and nitrogen fertilization increased turfgrass canopy reflectance as captured by NDVI.

Figure 4. Normalized Difference Vegetation Index (NDVI) given 2 or 3 Tenacity applications on a ‘HD Sport 2.0’ Kentucky bluegrass tee. Applications in 2023 were Aug 22 and Sep 6, 2022 (2 apps.) plus Sep 19 (3 apps.). Two applications (blue box) were as good as three applications. Fisher’s LSD (P<0.05). Bob Berry Sunshine Course, Lemont, IL

Final Photo

#Daffodils emerging and blooming in early spring, Bob Berry Sunshine Course, Lemont, IL. Settle, Apr 4, 2024 “Narcissi were well known in ancient civilisation, both medicinally and botanically, but were formally described by Linnaeus in his Species Plantarum (1753). The genus is generally considered to have about ten sections with approximately 36 species. The number of species has varied, depending on how they are classified, due to similarity between species and hybridisation.” Wikipedia has more

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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.