July Rain! Beryl, Peak Disease Pressure, Take-All Patch, and Nutsedge Research
In a week it was wet. Our predominately clay soils, that were already wet, then became saturated. An early, strong hurricane (Beryl) slammed into the Gulf Coast (Texas) this week. “Its remnants tracked northeast and reached western Indiana by the evening on Tuesday, July 9th. Rainfall amounts of 2 to 5 inches occurred across portions of central and eastern Illinois…” And that’s problematic when its July. Actually, that’s disastrous in July. However, any ‘grower fear’ was offset by what one can only describe as “unusually cool conditions for midsummer”. You can quote me on that. In a week, it felt less like summer and more like spring. When a summer season goes backwards? Those unusual conditions have meant a substantial amount of recovery from the usual turf thinning has occurred in the landscape in July.
Just open your eyes and you’ll see a tremendous amount of turfgrass growth has returned. Some are again “baling hay” in the roughs. And it doesn’t stop there. Lush Kentucky bluegrass lawns once again blanket Chicago’s suburbs. However, peak summer heat is in the forecast (90s), but some good news — we know it will be short lived. Nevertheless, our number one issue in 2024 is all about roots. The lack thereof. Golf course superintendents continue to scout for wilting patches of bentgrass. Highly maintained and trafficked areas are most vulnerable given both take-all root rot and Pythium root rot remain problematic in saturated soils. Timely preventative fungicide applications to target roots is a requirement. But periodic moderations of midsummer heat has become the redeemer in 2024 and when it’s hot, brevity is always a good thing if you are cool season turfgrass. Throughout the recent boomerang of temperatures, you should’ve noted two things. Our green space is resilient and those that enjoy the outdoors with a no-matter-what attitude are cool.
Weather
Scouting for Disease — Take-All Patch (Gaeumannomyces avenae)
Take-all patch continues to be on our list of aggravating issues for 2024. One reason is that recovery from most root rots is slow. Healthy roots must regrow and that takes time. A second possibility is that this summer has not consistently heated up — warm soil temperatures naturally suppress Gaeumannomyces the causal agent of take-all patch.
Solutions
Curative chemical control is not usually effective for take-all patch. Instead cultural practices that promote root growth are the way to go. However, now is the time to be thinking about preventative fall applications for take-all patch. See newest 2024 recommendations in PPA-1: Chemical Control of Turfgrass Diseases 2024 (uky.edu).
Scouting for Disease — Brown Patch (Rhizoctonia solani)
After dollar spot, brown patch caused by the fungus Rhizoctonia solani represents our most common disease we typically see in summer. July and August are the two months with greatest disease pressure in cool season turfgrasses. As is the case for dollar spot, the combination of summer heat (warm nights with +68 F degrees optimum) and high humidity (leaf wetness duration of 10 hours or greater) are ideal conditions for brown patch epidemics.
Resistance to Brown Patch in Cool Season Turf
- Severe Blight Occurs. Perennial ryegrass and tall fescue are highly susceptible to brown patch.
- Good Resistance. Creeping bentgrass has comparatively good resistance overall when it comes to brown patch.
- Best Resistance. Kentucky bluegrass is typically not impacted by brown patch.
Post Yellow Nutsedge Control with Arkon — Shehbaz Singh, MS
A PBI-Gordon funded herbicide trial to control yellow nutsedge in fine fescue roughs is being conducted at North Shore Country Club in Glenview, IL. Of weeds, nutsedge as group can be difficult to control because it does not respond to the common broadleaf herbicides that we use for weed control in turfgrass.
Therefore, yellow nutsedge represents an escape in out of play areas. Other herbicides are necessary to control sedges in turfgrass environments. Eventually become increasingly problematic without treatment. This study investigated a newer active ingredient and product named Arkon.
Material and Methods
The study is being conducted in a fine fescue area near putting green 14 at North Shore Country Club. The study has 4 treatments in a randomized complete block design with 4 replications. The first application for herbicides was made on June 11 and a second application will be made on July 15, 2024.
Objectives
- Evaluate post-emergent yellow nutsedge control of herbicides
- Evaluate turfgrass quality
- Monitor any phytotoxicity to turf
Measurements
- Yellow nutsedge control (%)
- Visual Quality (1–9 scale, with 6 = minimum acceptable and 9 = best)
- Normalized Difference Vegetation Index (NDVI) using GreenSeeker/Trimble HCS-100
- Phytotoxicity (%)
Yellow Nutsedge Control
Initial infestation of yellow nutsedge was about 55% for Dismiss, 40% for Arkon, 31.2% for Sedge Hammer, and 36.2% for untreated. After the first application on June 11, yellow nutsedge as reduced to 26.2% for Arkon, 16.2% for Sedge Hammer, and 1.25 % for Dismiss.
On July 9, yellow nutsedge had been reduced to near zero for both Dismiss and Sedge Hammer while it was 27.5% for Arkon. Arkon is different in that it is reducing yellow nutsedge more gradually. This is desirable because it allows time for the regrowth of fine fescue and a less noticeable transition occurs.
In contrast, untreated plots continue to remain with yellow nutsedge and levels have increased since study start to near 50%. Yellow nutsedge is tall (+12 inches) and its bright yellow color is objectionable.
Visual Quality and NDVI
Reduction in visual quality and NDVI data was observed one week after the initial application of herbicides. A reduction in visual quality was due to dying yellow nutsedge which attained a yellow to straw color. The effect was greatest for Dismiss and Sedge Hammer and the least for Arkon treated plots.
Short Video
Each week Dan Dinelli creates a lot of videos using Instagram at North Shore Country Club (northshorecc_grounds). The yellow nutsedge research was captured this week. Thanks Dan!
Final Image
“Asclepias incarnata, the swamp milkweed, rose milkweed, rose milkflower, swamp silkweed, or white Indian hemp, is a herbaceous perennial plant species native to North America. It grows in damp through wet soils and also is cultivated as a garden plant for its flowers, which attract butterflies and other pollinators with nectar. Like most other milkweeds, it has latex containing toxic chemicals, a characteristic that repels insects and other herbivorous animals.” For more see Asclepias incarnata — Wikipedia.
