Cool Weather Coming! Dollar Spot Surges, Golfers Delight (Dry) and Bentgrass Variety Research
The first week of “meteorological fall” began September 1st, but it didn’t exactly go that way. Instead, it was hot and it reminded us of summer with daytime highs in the upper 80s with a peak near 90 on Thursday in Chicago. Things were on pause. Recovery from summer stress would have to wait for Agrostis, Poa and Festuca. But not for long. The forecasted high for Saturday, September 7 is a chilly 67 degrees. With cool temperatures back in place, cool season turf only needs one more thing. Would it please rain?
If you grow turfgrass, a narrow window of time in the early fall provides optimum conditions for throwing seed. “Adequate soil moisture, warm soil, and limited weed pressure allow for excellent seedling growth. Between August 15 and September 15 is optimum seeding time in the northern half of Indiana and Illinois.” says a Purdue and University of Illinois fact sheet. On the golf course conditions are as good as it gets, but of course that depends on your perspective. For example, researchers of creeping bentgrass prone to dollar spot can now enjoy a final surge in disease pressure — in the name of science. Golf course superintendents are now pivoting their attention and labor to broadleaf weed control, mowing of naturalized fineleaf fescue areas, and fall projects like detailing sand bunkers. And golfers are smiling given playing surfaces have remained dry for about a month now. If asked when were the best playing conditions in 2024? The correct answer is right now.
Weather
Scouting for Disease — Dollar Spot (Clarireedia jacksonii) will predominate from here on out.
Dollar spot is the most chronic disease that golf course superintendents deal with. And more fungicides are used to control this single disease of turfgrass.
Most cool season turfgrass is susceptible to varying degrees. Unfortunately creeping bentgrass can be highly susceptible. That can mean large acres of that require fungicide applications because creeping bentgrass is used extensively from tee to green in the upper Midwest. However, newer dollar spot resistant varieties of creeping bentgrass are increasing available.
Creeping Bentgrass Varieties for Dollar Spot Resistance & Reduced Inputs by Shehbaz Singh, MS
A creeping bentgrass variety trial has been established at Bob Berry Sunshine Course in Lemont. Initially seeded on Aug 31, 2023 the turfgrass is now one year old and fully established.
Site & Creeping Bentgrass Varieties
The site is a USGA specification rootzone which was previously used for two creeping bentgrass putting green variety trials. The first was a 2004–09 National Turfgrass Evaluation Program (NTEP) and the second was a 2009–2012 North Central Region study (NCERA 192) — a collaboration of turfgrass university scientists that represent the Midwest. The current trial has a total of 20 creeping bentgrass varieties in a randomized complete block design with four replications.
Objectives
- Evaluate establishment rate
- Evaluate dollar spot susceptibility
- Evaluate other desirable characteristics such as spring green up
Materials & Methods
- Plots (4 ft x 8 ft) were hand-seeded on Aug 28, 2023, at a rate of 1 lb per 1000 sq ft*. Slow-release fertilizer mixed with seed (Forever Green natural, 4–3–0). *‘Match Play’ and ‘Spectrum’ by Landmark Seed were seeded on April 30, 2024.
- Grow in received minimal inputs — Nitrogen by liquid urea (0.15 lbs N per 1000 sq ft) applied in the fall of 2023 (Oct 4, Oct 10, and Oct 19). Fungicides were not needed/not applied during establishment.
- Forever Green Natural 4–3–0 slow release fertilizer was applied monthly at 0.5 lbs N per 1000 sq ft in 2024 (Apr 16, May 21, and Jun 20, July 18, and Aug 29).
- During 2024, fungicides to address dollar spot would occur as needed using a post-infection strategy. Curative fungicide applications would not occur until a variety reached an average damage threshold of 10%.
Visual Data Collection (every 14 days)
- Dollar Spot (% and number per plot)
- Turf Quality (1–9 scale, with 6 = minimum acceptable and 9 = best)
- Turf Cover (% per plot)
- Spring Greenup (1–9 scale, with 6 = minimum acceptable and 9 = best)
- Winter/Dormant Turf Discoloration (% per plot)
- *Normalized Difference Vegetation Index or NDVI using GreenSeeker / Trimble HCS-100* (canopy reflectance of far red and near-infrared light wavelengths). *Electronic measurement for reference
Dollar Spot Update — Sep, 2024
Dollar spot disease development is now at peak levels in the creeping bentgrass variety trial. Currently (Sep 4) dollar spot infection centers surpassed the threshold of 10% per plot, but only in a few of the creeping bentgrass entries. A curative fungicide application will occur to those varieties alone. There was no statistical difference among entries for dollar spot disease. Nevertheless, trends were observed.
Dollar Spot levels greater than 10% (5 total)
- Pure Distinction, Piranha, PST-RODS, Pure Eclipse, and Puregreen
Dollar Spot levels 5 -10% (8 total)
- 777, Barracuda, 007, 007XL, Piper, PST-0DSF, PST-0MRN, and PST-0R20
Dollar Spot levels less than 5% (4 total)
- Centennial
- Oakley
- Macdonald
- Mackenzie
To Date No Fungicides Applied
All varieties are about 1 year in age except the newly added varieties of Spectrum and Match Play. No fungicide application has ever been made. As previously mentioned, this creeping bentgrass variety trial is investigating dollar spot resistance and the environmental benefits therein. Therefore, only minimal fungicide applications will be made.
1st Fungicide Application Scheduled for Sep 10, 2024
On average, five creeping bentgrass varieties were found to have dollar spot levels greater than our acceptable threshold of 10%. Our first curative application of Daconil Action (chlorothalonil) is now scheduled for those entries in all four replicates.
Dollar Spot Percent (per plot)
Dollar Spot Count (per plot)
Visual Quality and NDVI
No statistical differences were observed between creeping bentgrass varieties for visual quality. In most cases, varieties with visual quality greater than 6.0 were those with lower levels of damage by dollar spot. In general similar trends were also observed by NDVI.
Visual Quality 6.0 or Greater (9 total)
- Centennial, 777, Barracuda, Macdonald, Oakley, Piper, PST-0DSF, PST-0MRN, and PST-0R20
Brown Patch
During August and September, brown patch was also observed in the creeping bentgrass variety trial. When rated on Sep 4, certain varieties had levels greater than 10% brown patch.
Brown Patch 10% or greater (7 total)
- Mackenzie, Flagstick, 007, Piranha, PST-0DSF, PST-0R20, and Pure Eclipse
Final Image
“Osteospermum are popular in cultivation, where they are frequently used in summer bedding schemes in parks and gardens. Numerous hybrids and cultivars have been grown with a wide range of tropical colors. Modern cultivars flower continuously… The genus Osteospermum was named by Carl Linnaeus in 1753. The scientific name is derived from the Greek osteon (bone) and Latin spermum (seed).” For more see Osteospermum — Wikipedia
