Dry Weather! 1st Grub Damage, Summer Patch, Fairway Fairy Ring, and Warm Season Turfgrass Research
It’s always about the weather — especially true if you are an outdoor enthusiast. Count me in. That forecast did not disappoint, it was a nice one. Actually, August’s third week was beyond nice. It was fabulous! Cooler temperatures gave a taste of fall (70s highs/50s lows). And August’s other main feature? It’s been dry. That’s been welcome and in stark contrast to July — it rained on 26 of 31 days. As one might expect, the current dry down we’ve experienced has been significant. One noticeable change is that automatic irrigation systems in every neighborhood are up and running. Up to now, supplemental watering of established lawns wasn’t necessary.
In the landscape, a white clematis called ‘Sweet Autumn’ (a long standing favorite perennial vine) has begun to flower. August’s early shift to fall (and drier conditions) has begun to have impact on larger areas of golf courses. For example, maintaining consistent soil moisture levels in creeping bentgrass fairway areas just became really tough. As usual, a few factors are at play. Native predominately clay soils are interacting with a stoloniferous creeping bentgrass surface and worst affected areas are associated with concentrated traffic. About now, you will see a dramatic increase of irrigation use on golf course fairways and tees. Precise water management is in the job description if you are to successfully maintain playing surfaces which, more often than not, are large acres of non-homogeneous turfgrass (a mixture of species). For sure, precision irrigation is most important during periods of peak summer heat. As it turns out, 90s for highs with heat indices of 100–105 is our forecast. This level of heat has been largely absent in 2024. Get ready?!?
Weather
Scouting for Insects — Annual White Grubs
Our first report of white grubs, and associated damage, was reported on a golf course fairway in Chicago this week. It turns out the root damage caused by white grubs (various beetle larvae) isn’t the biggest problem.
A greater issue is when skunks and racoons search for a favorite food (grubs). Curative insecticide treatment is necessary to avoid severe damage courtesy of Pepe’ Le Pew.
Excellent Fact Sheet — Purdue University
Managing White Grubs in Turfgrass by Douglas S. Richmond
Scouting for Disease — Summer Patch (Magnaporthiopsis poae)
Summer patch (a root, crown and stem disease of bluegrasses) hasn’t been much of an issue in 2024. That appears to have changed. Drier conditions in association with soil compaction (high traffic areas) are beginning to see development of summer patch symptoms.
Roots likely infected during our record wet July. Wet soils both hurt us (root rots are active) and help us (will act to mask the symptoms of root loss).
Scouting for Disease — Fairy Ring (various Basidiomycete fungi)
Fairy ring is often associated with localized dry spot (LDS). Both can be more problematic in the root zone when conditions are dry. In August, it has become an increasing issue in fairway situations. Cultural practices and well as fungicides and wetting agent are useful when combating abnormal soil wetting and drying caused in part by a build up of fungal mycelium in a zone beneath the ring.
Evaluating improved cold-tolerant bermudagrass and zoysiagrass for golf tee use in Chicago. by Shehbaz Singh, MS
A warm season turfgrass study is being conducted at the Bob Berry Sunshine Course in Lemont, Illinois. It is testing improved varieties of bermudagrass and zoysiagrass (also known as C4 turfgrass) for use on golf courses in Chicago. This study is being conducted on a tee surface which represents sand-capped rootzone with native soil beneath. The existing colonial bentgrass plus creeping bentgrass tee surface was killed using a single application of glyphosate at its label rate on April 11, 2024. The existing dead thatch layer was retained to aid C4 turfgrass establishment. It will help to prevent weed seed germination, retain soil moisture, maintain a consistent mowing height, and allowed continued use as a playable tee surface.
Material and Methods
The study is being conducted in a randomized complete block design with treatments consisting of 8 warm season turfgrass entries (4 bermudagrass and 4 zoysiagrass). Treatments are replicated five times and individual plot size is 5 ft x 5 ft. Establishment used 4 inch diameter plugs of bermudagrass and zoysiagrass. In 2024, a total of two bermudagrass plugs of each bermuda variety were planted per plot on May 22. One week later, a total of four zoysiagrass plugs of each zoysia variety were planted per plot on May 29. After two weeks of establishment, regular mowing began at tee height with a Toro triplex reel mower (Cog Hill Golf & Country Club, Lemont, IL). Additional details are below.
- Slow-release granular fertilizer, Forever Green Natural 4–3–0, at 0.5 lbs N per 1000 sq ft applied on July 9, 2024. Applications are timed monthly during the summer season to ensure optimum growth.
- Herbicides were infrequently used to reduce competition by weeds. A single application of Switchblade at 4 pints/acre to address broadleaves occurred on July 3 (PBI Gordan, Kansas City, MO). A single application of Revolver at 0.4 fl oz/1000 sq ft to selectively remove annual bluegrass occurred on July 25 (Envu, Carey, NC).
- Weekly, a hand edger tool is used to prevent entries from intermixing and thus maintain plot boundaries.
Objectives
- Evaluate establishment/lateral spread
- Evaluate persistence/cold tolerance
- Evaluate spring green up
- Evaluate dormant color retention
Data
For data collection, the best individual plug was selected for measurements in each plot. NDVI is used to supplement all visual ratings of color (TCM 500 Color Meter, Spectrum Technologies, Inc.)
- Lateral spread (in.) — Maximum stolon length from plug center
- Turfgrass Persistence — Visual cover (% per plot)
- Fall Color Retention — Color rating (1–9, 9 = dark green)
- Spring Green Up — Color rating (1–9, 9 = dark green )
Lateral Spread
For most bermudagrass entries, lateral spread began a week after transplanting into plots on May 22. For zoysiagrass entries, lateral spread was first noticed the last week of July and only ‘Innovation’ zoysiagrass displayed lateral stolons.
Overall, bermudagrass showed greatest lateral spread when compared to zoysiagrass.
Visual Green Color
Bermudagrass: All bermudagrass entries had acceptable green color (6.0 or greater) on most rating dates in the summer. Among bermudagrass entries, ‘Tahoma31’ and ‘OSU1629’ had a darker green color with a visual rating higher than ‘7’ on most dates while ‘OKC3920’ and ‘OSU15x9’ had a relatively lighter green color.
Zoysiagrass: Most zoysiagrass entries did not have acceptable green color (6.0 or greater) during June. From July on, zoysiagrass’ green color was acceptable. ‘Meyer’ and ‘DALZ1701’ showed a relatively darker green color on most rating dates.
Normalized Difference Vegetation Index (NDVI)
NDVI is an electronic way to evaluate turfgrass health. It is useful because different users can gain the same exact data whereas visual quality ratings are subjective/dependent on a well-trained individual. NDVI uses canopy reflectance of far red and near-infrared wavelengths. In general, NDVI followed the same trends as visual color.
Final Image
“Clematis terniflora is a vine with opposite, pinnately compound leaves, on climbing stems. The flowers are white, borne in fall. The blooms are nicely fragrant and visited by bees. In late fall, the fertilized flowers become fruit (seed) clusters of 5–6 fruits connected at the heads and each having a long white tail. As these dry, the color of the fruits fade and the tail becomes feather-like. In the spring the fruits detach and are dispersed by wind.” For more see Clematis terniflora — Wikipedia
