Summertime! Traffic?!?, More Take-All Patch, Heat Stress, and Broadleaf Weed Research

Like a lyric from the Porgy and Bess song from George Gershwin’s opera it finally happened. Summertime. Summer officially arrived June 20, and that’s great for warm season turfgrasses like zoysia and bermuda. And not so great for cool season stuff like annual bluegrass (Poa annua) which is always a component of tees, fairways and greens. It means maintenance becomes more immediate especially when it comes to water management in sand-based putting greens or else midday wilt stress will damage. The decision of when (and where) to water has been notched up — soil moisture is electronically monitored prior to hand-watering. Otherwise we risk a root demise in bentgrass greens called Pythium root rot. Here goes nothin’.

Image 1. Turf type tall fescue is unfazed during a period of early peak summer heat in Chicago. Well adapted for use on a steep bunker faces which can surround sand bunkers. Midlothian Country Club, Midlothian, IL. Settle, Jun 20, 2024

In the landscape, you should have noticed native Illinois flowers about now. It turns out they are adapted to both heat and drought tolerance. Makes sense. We’ve also begun to see many Chicago lawns looking toasty. They can’t help it. When establishing a lawn, selecting a turfgrass species with superior attributes is paramount. Any vulnerability will be most pronounced in the summer months. I was reminded of this by a university colleague at a recent meeting in Madison, Wisconsin (NCERA-221). Fescues perform much better when it comes to drought tolerance. It‘s their genetics and the physiological strategies therein (deep roots). Now what about golf course superintendents and staff? They have to deal with a mixed bag of turfgrass every summer. A monostand of heat- and drought-tolerant turf isn’t what they get. And that is where the skill set of adjusting (quickly) to changing environmental conditions (e.g., July heat in June) is not an elective, it’s a requirement. Meanwhile golfers can now enjoy some of the best playing conditions from tee to green as we finish June. Why? It’s dry!

Weather

Figure 1. June becomes July! Hot days remain in the upcoming forecast. Bob Berry Sunshine Course, Lemont, IL

Figure 2. Chicago sees a string of 90+ high temperatures in June and more are in the forecast. Graphic courtesy WGN

Scouting for Environmental Stress— Traffic versus Wilting Turf (don’t do it)

Well it doesn’t take long to see what happens when turf is trafficked when stressed. I saw it this week on a ‘007’ creeping bentgrass fairway in Lemont, Illinois.

Image 1. Creeping bentgrass at low mowing heights is especially sensitive to injury by traffic during midday wilt stress. Bob Berry Sunshine Course, Lemont, IL. Settle, Jun 20, 2024

Watch It! Golf cart traffic and drought have a significant effect on turfgrass; here’s how you can help

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Golf Cart Use in Summer

• Increased cart traffic can take a toll on turf, especially during periods of drought.
• It is estimated that the area of turf impacted by a golf cart carrying one or two golfers is 48 times the greater than the area affected by foot traffic.
• It is easy to count the revenue generated by golf cart rentals, but it is not so easy to account for the damage and additional maintenance required to compensate for unrestricted cart use.

Tips for Golf Cart Use During Stressful Conditions

1. Please practice the daily policy at your course. Cart traffic policies vary from course-to-course, hole-to-hole and even day-to-day. Slowly growing turfgrass is more vulnerable to heavy cart traffic.
2. Avoid driving over dry or heat stressed turf. Cart traffic during hot, dry weather should be carefully monitored, as it can cause severe damage. The resultant tire marks often take weeks to heal during the summer.
3. Do your best to steer clear of high-traffic areas. Sometimes it’s better to take the road less traveled. Most cart damage appears in areas where traffic is concentrated, like the ends of cart paths.

Scouting for Disease — Take-All Patch (Gaeumannomyces avenae)

Our number one fungal disease in June is officially a root rot known as take-all patch. It impacts creeping bentgrass fairways.

Notes on Take-All Patch (TAP)

• It is unusual to see this much take-all-patch and is likely related to conditions conducive for its development this spring — wetter than normal and we experienced an extended period of cool temperatures during May and into early June.
• The good news is that warmer summer soil temperatures will naturally suppress the disease.
• Most curative fungicide applications will not result in quick recovery because the damage (root rot) is already done.
• Symptoms within portions of creeping bentgrass fairways are most associated with heavy clay soils where compaction is a chronic issue.

Image 1. Take-all Patch in a creeping bentgrass fairway. It causes damage that frustrates golf course superintendents. Settle, Jun 20, 2024

Image 2. The actual patches caused by take-all patch in creeping bentgrass are not always textbook. Some will have an almost spotty look. At times this is because Poa annua has colonized the interior of the patch and it’s roots appear immune/less susceptible. Settle, Jun 20, 2024

Image 3. Native soils with a large portion of clay is most often associated with take-all patch in fairways. Settle, Jun 20, 2024

Heat Stress 101

Temperature above the optimal range can occur for prolonged periods during summer. We sometimes just say supraoptimal temperatures. “Heat stress has been considered the primary environmental factor, causing decline of cool-season grasses in the summer, although many other factors can be involved.” Fry and Huang, Applied Turfgrass Science and Physiology, 2005

Heat Stress Facts

• Air and soil temperatures often reach supraoptimal levels in summer
• Supraoptimal temperatures limit shoot and root growth
• Heat stress for cool season turfgrasses = above 86 F
• Heat stress for warm season turfgrasses = above 113 F
• Heat stress symptoms are often confused with pathological problems in cool-season turfgrass = yellowing and thinning with root dieback

Figure 1. Root images recorded with a minirhizotron camera at a 1.2 inch soil depth from Jun to Oct. The take home message is that a natural root loss occurs during the mid-summer months (Jul and Aug) when soil temperatures are supraoptimal. Roots return when soil temperatures cool (Sep and Aug). The turfgrass was Crenshaw creeping bentgrass in Manhattan, KS. Courtesy Fry and Huang, 2005

Relative Heat Resistance

Table 1. Relative heat resistance of cool-season grasses to indirect heat stress. Modified from Fry and Huang, 2005

Cultural Practices for Heat Stress/Summer Decline of Greens — Encourage Root Growth #1

• Aerify throughout the summer with needle tines or spikers
• Syringe with water to lower the canopy temperature
• Improve air movement by removing trees or using fans around greens
• Spoon feed with water-soluble nutrients
• Raise mowing heights to increase photosynthetic activity
• Chose rolling instead of mowing greens
• Reduce mowing frequency when turfgrass isn’t growing (lessens equipment wear)
• Stop mowing putting green clean up laps when turfgrass isn’t growing

Post-emergence control of white clover in a golf course rough. by Shehbaz Singh, MS

A herbicide trial to control white clover in an existing Kentucky bluegrass rough is being conducted at Bob Berry Sunshine Course, Lemont, IL.

Study Sponsor

Nufarm

Image 1. A herbicide study to control white clover in a Kentucky bluegrass rough. Near Fairway 1 at the Bob Berry Sunshine Course, Lemont IL. Singh, Jun 21, 2024

Materials and Methods

The study is a demonstration trial for the upcoming Nufarm turfgrass field day in July at the Bob Berry Sunshine Course, Lemont, IL. The study is being conducted as a non-randomized complete block design with 5 herbicide treatments and 3 replications. Each treatment was split and applied either once or twice. All replicated plots for a particular treatment are grouped in one block for demonstration purposes. The first application for herbicide treatments was made on May 11, 2024, and the second application was made on June 13, 2024.

Objectives

• Evaluate white clover control using herbicides
• Compare one application versus two applications
• Monitor any herbicide phytotoxicity to turf
• Evaluate visual weed injury

Table 1. Treatments for a Nufarm white clover study. The first application was made on May 11 and a second application was applied on June 13, 2024. Bob Berry Sunshine Course, Lemont, IL

Measurements

• Visual Quality (1–9 scale, with 6 = minimum acceptable and 9 = best)
• Normalized Difference Vegetation Index (NDVI) using GreenSeeker/Trimble HCS-100
• Visual White Clover Infestation (%)
• Visual Phytotoxicity (%)

White clover control with one application

With one application, weeder 64 and Triad Select was unable to control white clover much compared to untreated. White clover control was seen for Primetime from 60% to 20% and Triplet from 70% to 30% for 2–3 weeks after application on May 11. However, white clover saw recovery and increase at 4 weeks from initial application for both PrimeTime and Triplet broadleaf herbicides.

White clover control with two applications

With two applications spaced 1 month apart, control of white clover was observed for all herbicide treatments. PrimeTime reduced white clover infestation from 76.6% to 21.6% and Triplet from 69.37% to 22.3%. Both saw good control following the first application as well as the second application.

Weedar 64 and Triad select showed greatest reduction in white clover infestation only after the second application. Weedar 64 showed white clover reduction from 85% to 38.33% after the second application date. Triad Select showed white clover reduction from 64.5% to 38.33% after the second application date.

Figure 1. A) Percent white clover given one application (May 11, 2024), and B) percent white clover given two applications (May 11 and June 13, 2024), Bob Berry Sunshine Course, Lemont, IL.

Normalized Difference Vegetation Index

Reduction in NDVI values occurred for both one-application and two-application herbicide treatment strategies. The reduction in NDVI values was mostly due to dying white clover plants which attained a yellowish to brown color.

However, a phytotoxic effect on turfgrass did occur for a treatment. For example, NDVI was reduced by PrimeTime for 2 weeks after the first application on May 11. NDVI also was reduced after the second application on June 13.

Figure 2. A) NDVI given one application (May 11, 2024), and B) NDVI given two applications (May 11 and June 13, 2024), Bob Berry Sunshine Course, Lemont, IL.

Visual Color

A reduction in visual green color was observed for all herbicide treatments. However, a higher reduction was observed when two applications were made. Visual color for PrimeTime plots was reduced in both one application and two application strategies. Reduction in visual green color was mostly due to dying white clover but was also due to a temporary phytotoxicity effect on turfgrass.

Figure 3. A) Visual color given one application (May 11, 2024), and B) visual color given two applications (May 11 and June 13, 2024), Bob Berry Sunshine Course, Lemont, IL.

Final Image

Common milkweed is just about ready to flower on the edge of a large naturalized flower area at the O.J. Nore Research Station in Verona, WI. Settle, Jun 18, 2024

“Asclepias is a genus of herbaceous, perennial, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. Most species are toxic to humans and many other species, primarily due to the presence of cardenolides. However, as with many such plants, some species feed upon them (e.g. their leaves) or from them (e.g. their nectar). The most notable of them is the monarch butterfly, which uses and requires certain milkweeds as host plants for their larvae.” For more see Asclepias here.