Backward Spring Goes! Cold, April Showers, Yellow Patch and Tenacity Research
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.
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
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.
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.”
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.
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%.
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%).
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).
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.
Final Photo
