June Heat! Soil Temps Above 70, Knotweed, Bentgrass Variety Trial
Warmer and dry conditions dominated most of the week following last week’s rainfall. Finally, creeping bentgrass has shown accelerated growth. Meanwhile, fine fescues in out-of-play areas are now producing abundant seedheads, giving courses both a distinct and desired appearance. Despite the warmer weather, warm-season grasses especially bermudagrass at Sunshine Course in Lemont, are showing limited green-up. This was likely due to winter kill and is consistent with findings from a recent U.S. survey by turf scientists at Purdue University. Large areas of bermudagrass and zoysiagrass were slow to green up, and some did not recover at all.
Soil temperatures across the Chicago area have now risen above 70°F, creating favorable conditions for several turfgrass diseases. This week, suspected take-all patch symptoms were reported in creeping bentgrass fairways in metropolitan Chicago. It’s that time of year and superintendents will remain vigilant in their scouting, as warm conditions can accelerate the symptom development of take-all patch disease in creeping bentgrass. Weekly scouting on Chicago’s north side has revealed third-instar and fifth-instar annual bluegrass weevil (ABW) larvae in collars of greens. This developmental stage marks the transition from internal stem feeding to external crown feeding, making it a critical point for turf damage. Larval activity in collars and approaches can lead to thinning, yellowing, and patchy turf collapse, often mistaken for drought stress or a disease called anthracnose. As our scouting for turf health ramps up, so too does the game of golf as it’s getting to be that time of year. Enjoy!
Weather
Scouting for Broadleaf Weeds — Prostrate Knotweed (Polygonum aviculare)
Prostrate knotweed is a low-growing, summer annual broadleaf weed commonly found along compacted paths, cart tracks, and high-traffic areas on golf courses.
Identification
Several characteristics can be used to help identify prostrate knotweed.
- Sprawling, wiry stems that form dense mats.
- Small, lance-shaped leaves are arranged alternately along the stem.
- Produces small white-pinkish flowers in leaf axils (late spring to summer)
- Develops a strong, deep taproot that allows it to tolerate drought and resist physical removal.
- Thrives well in compacted, dry soils and areas with poor turf density.
Chemical Control
Post-emergent chemical control, including herbicides products containing dicamba, 2,4-D, or triclopyr, is quite effective in controlling Prostrate knotweed. Pre-emergent herbicides like dithiopyr or isoxaben are effective in controlling prostrate knotweed with late fall application.
Cultural Control
Cultural practices for long-term suppression of prostrate knotweed:
- Alleviate soil compaction through core aeration.
- Minimize traffic in problem areas using barriers or alternate routing.
More Information
For more detailed information on black medic, please refer to the Prostrate knotweed factsheet by Dr. Aaron Patton, Purdue University.
NCERA-221 Annual Meeting 2025 — Turfgrass Science
This week, after completing our turfgrass research work with the CDGA program on Monday, we traveled to Columbus, Ohio, to attend the 2025 NCERA-221 (North Central Extension and Research Activity) annual meeting hosted at Ohio State University. The meeting brought together turfgrass researchers, extension specialists, and industry partners to advance multistate collaboration focused on improving turfgrass management across the North Central region. It featured research presentations, project planning discussions, and the development of new initiatives aimed at reducing inputs, enhancing sustainability, and expanding outreach. Key topics included a bermudagrass and zoysiagrass winterkill survey, a dollar spot research update, organic weed control, low-input and pollinator-friendly lawn strategies, clover lawns, and regional turfgrass cultivar selection guides. State-level program updates were also shared, with an emphasis on improved communication and sustained collaboration moving forward.
Creeping Bentgrass Varieties for Dollar Spot Resistance & Reduced Inputs
A creeping bentgrass variety trial has been established at Bob Berry Sunshine Course in Lemont. The site is a USGA specification rootzone that was previously used for two creeping bentgrass variety trials. 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
- Each plot (4 ft x 8 ft) was hand-seeded on Aug 28, 2023, at a rate of 1 lb per 1000 sq ft* *Landmark Seed Company Match Play and Spectrum bentgrasses were seeded on April 30, 2024
- Slow-release fertilizer was mixed with seed (Forever Green Natural, 4–3–0)
- Grow in of bentgrass saw minimal inputs; 0.15 lbs N per 1000 sq ft as liquid urea in 2023 (Oct 4, Oct 10, and Oct 19).
- Slow-release fertilizer (Forever Green Natural, 4–3–0) 0.5 lbs N per 1000 sq ft per month was applied in 2024 (Apr 16, May 21, Jun 20, Jul 18, Aug 29, and Oct 9)
- Slow-release fertilizer (Forever Green Natural, 4–3–0) 0.5 lbs N per 1000 sq ft per month was applied in 2025 (Apr 8, May 6, and Jun 4)
Data Collection– Every two weeks
- Visual Quality (1–9 scale, with 6 = minimum acceptable and 9 = best)
- Normalized Difference Vegetation Index (NDVI) using GreenSeeker/Trimble HCS-100
- Dollar Spot (% and number of spots per plot)
- Winter Desiccation of Dormant Turf (% per plot)
- Spring Green-up (1–9 scale, with 6 = minimum acceptable and 9 = best)
- Green Color (% per plot)
Spring Green-Up —Jun 2025
Creeping bentgrass has finally started growing. However, only a few varieties have shown acceptable visual green-up ratings. A majority still lack density and green color.
Acceptable Spring Green-up: Visual rating > 6
- Matchplay, Piper, and PST-0R20
‘Middle of the Pack’ Spring Green-Up: Visual Quality > or = 5 and < 6
- 777, Macdonald, Barracuda, Centennial, Oakley, Spectrum, Pure Eclipse, Puregreen, Mackenzie, 007XL, Piranha, PST-RODS.
Slowest Green-up: Visual rating < 5
- 007, PST-0DSF, PST-0MRN, Pure Distinction, and Flagstick.
Percent Green Color
Variety with Percent Green Color > 70 (best)
- Matchplay, PST-0R20, Piper, and 777
Variety with Percent Green color < 60 (worst)
- Flagstick and 007
Education & Communication by CDGA’s Green Committee
Final Photo
“Viburnum dentatum, southern arrowwood or arrowwood viburnum or roughish arrowwood, is a small shrub, native to the eastern United States and Canada from Maine south to northern Florida and eastern Texas. Native Americans used the young stems to make arrow shafts.” For more see Wikipedia
