Cloudy! Bentgrass Woes, Cicadas, 1st Dollar Spot, Honey Bees, and Shear Strength Research

CDGATurfgrassProgram
10 min readMay 17, 2024

Patience!?! May is a month that can be problematic for golf course superintendents as far as greens go. But you probably wouldn’t know it unless you ask them. The last hurdle we have to cross during this spring shoulder season is May. Creeping bentgrass greens are finicky about temperatures and like to wait — cloudy conditions in May can be frustrating. The further north, the longer the wait. Unlike Poa or annual bluegrass, a cool temperature specialist that’s first out of the gate in April, bentgrass doesn’t see optimal growth until late May/early June in the upper Midwest. Or as a golf course superintendent said this week, “Creeping bentgrass will start growing when the periodical cicadas emerge.” I learned two things. 1) A new phenological indicator is born! 2) Creeping bentgrass greens require patience in May.

Image 1. Too much cloud cover slows spring growth of Penn A1 plus Penn A4 in a couple ways: 1) Threshold light levels necessary for photosynthesis are reduced and 2) “Low thick clouds reflect solar radiation and cool the surface of the earth”, courtesy NASA. Settle, May 9, 2024

In the landscape this week, there are more and more perennials to see. Bearded iris, I. germanica, is now blooming in a wide range of colors. In other news, there’s been a lot of anticipation, talk (and excitement) about emergence of periodical cicadas, Magicicada sp., in Illinois. It only happens every 13 or 17 years. A week ago they were reported in the southeastern United States — places like Tennessee. And this week Illinois soils warmed into the mid 60s and as expected… Magicicada arrived in southern and central portions of the state. As the week wore on, first sightings of periodical cicadas were also reported in Chicago’s suburbs. For more on periodical cicadas see April’s Chicago District Golfer ‘Turf Column’ The Cicadas Are Coming! Don’t Panic. A quote this week seemed especially relevant, “Male cicadas can reach decibels similar to a lawn mower or passing jet…”. For the next 4–6 weeks enjoy the game of golf. It will enjoyable AND it will be loud?

Weather

Figure 1. Soil temperatures have now stabilized at 65 degrees. A key temperature for soil fungicide applications for summer patch — a common root rot disease of bluegrass. Bob Berry Sunshine Course, Lemont, IL
Figure 2. Frequent rains have influences a few things needed for growing 1) cooler temperatures and 2) low light levels due to cloud cover, Bob Berry Sunshine Course, Lemont, IL
Figure 3. April Cloud Cover Data: “Looking at Earth from outer space, clouds are easy to spot. Clouds are draped all around Earth like bright white decorations. Clouds are important to scientists because they reflect the Sun’s light back to space and give shade to the surface. They also bring rain, which is important because all plants and animals need freshwater to live. These maps made from NASA satellite observations show how much of Earth’s surface is covered by clouds for a given day, or over a span of days.” Courtesy NASA

Scouting for Disease — 1st Dollar Spot of 2024

Our first report of dollar spot development occurred this week in Chicago. Fungicide sprays will now begin to address this our most chronic disease of both creeping bentgrass and Poa annua.

Image 1. Initial signs of dollar spot is the appearance of white, fluffy mycelium. On golf greens Poa annua is highly susceptible as is creeping bentgrass. Newer creeping bentgrass varieties now have good to excellent levels of resistance to dollar spot Disease. Courtesy Chicago GCS, May 17, 2024

A concerted effort by leading turfgrass breeders to improve dollar spot resistance has worked. Newer varieties of creeping bentgrass have good to excellent levels of resistance. Back in the day, circa 2000, ‘L-93’ represented one of the only creeping bentgrass varieties which had been bred and then selected for genetic resistance to dollar spot. The CDGA Turfgrass Program is currently investigating the newest varieties in a replicated nursery green trial in Lemont. Stay tuned.

Image 2. A creeping bentgrass variety trial establishing at Bob Berry Sunshine Course in Lemont, IL. This study will focus on understanding the dollar spot resistance of new varieties as well as experimentals not yet available. Settle, May 11, 2024

Fungicide Recommendations for Dollar Spot (use university data)

Click link & see pages 15–17. Chemical Control of Turfgrass Diseases 2020

Scouting for Weeds? Teasel (Dipsacus sp.)

It is still time for herbicide spot treatments to address broadleaf weeds. Again, at this time plants are still in the juvenile state and much easier to control.

Another broadleaf you should be scouting for is something called teasel — not to be confused with thistle. First introduced to me about 2006 by Dr. Randy Kane on Sunshine Course in Lemont. And I saw it every year thereafter! A common weed in Illinois; especially along roadsides.

Image 1. Teasle is a bienniel plant. Here are the different stages growing along a fenceline. Older dry seedheads are from the previous year and look somewhat like thistle seedheads. The rosettes (foreground) will go to seed this growing season, Bob Berry Sunshine Course, Lemont, IL. Settle, May 9, 2024
Figure 2. A teasle rosette is large and easy to identify. Sunshine Course, Lemont, IL. Settle, May 9 2024

Teasle or Dipsacus species are native to Europe. And so it is considered an invasive species in the United States. The USDA has a website called the National Invasive Species Information Center. It provides a brief series of bullet points linked to scientific references for further reading. See below

National Invasive Species Information Center — Common Teasle

  • Scientific Name: Dipsacus fullonum L. (ITIS)
  • Common Name: Common teasel, wild teasel, Fuller’s teasel, venuscup teasel
  • Synonym: Dipsacus sylvestris Huds. (ITIS)
  • Native To: Europe (Gucker 2009)
  • Date of U.S. Introduction: First cultivated in the U.S. during the 1800s (Gucker 2009)
  • Means of Introduction: Was cultivated for use in textile processing, or may have been introduced accidentally with other varieties of teasel (Gucker 2009; Bentivegna and Smeda 2008)
  • Impact: Crowds out native species (Gucker 2009)

Teasel Fact Sheet from the University of Illinois

Beware of the Invasive Teasel Plant by Douglas Gucker. “During its rosette stage, which can last longer than a year, it develops a large taproot and large basal leaves. During the flowering stage, it sends up a stalk with several seed heads that may reach over seven feet tall. Each plant will produce about 2000 large seeds. It grows well in sunny areas and likes moist to dry soil conditions.”

Honey Bees Introduced to Sunshine Course

We are beginning a demonstration study on Bob Berry Sunshine Course in Lemont, IL which looks at going beyond fine fescues in out of play rough areas.

Illinois Native Flowers

The primary objective is to establish native Illinois flowers in out-of-play areas. We are fortunate to have the advice and direction of Dave Ward. Dave is the former golf course superintendent of Coyote Run Golf Course in Homewood, IL. See his April, 2020 article titled A New Use For Old Bunker Sand.

Pollinators

A secondary objective is to collect information on pollinators. To that end, we’ve recently introduced honey bees to Bob Berry Sunshine Course. We thank the technical assistance and material support of Honey Lake Bee Company which is owned and operated by Brian and Karen Thomson and is located in North Barrington, IL. The bees we are using are called Italian honey bee. Specifically they are Apis mellifera ligustica which is a subspecies of the western honey bee (Apis mellifera).

Grant

The FairWays Foundation is funding this demonstration project. “Environmental stewardship is not an initiative. It is a long-term investment into our future and the future of our industry. The FairWays Foundation directly funds local and global projects that advance the conservation of our natural resources. These projects help to preserve the environment we live and work in whilst encouraging education and stewardship not only within our own industry but also within wider communities.”

Image 1. Two honey bee nucs are transferred into bee hive frames, Bob Berry Sunshine Course, Lemont, IL. Settle, May 11, 2024
Image 2. Honey bees are labeled and barriers (wood stakes) with signs inform golfers of their presence, Bob Berry Sunshine Course, Lemont, IL. Settle, May 11, 2024
Image 3. The bees immediately begin to forage various flowers in bloom in May. For example, white clover has just started to bloom. In 2024, it will be allowed to grow in all Kentucky bluegrass roughs, Bob Berry Sunshine Course, Lemont, IL. Settle, May 11, 2024

Shear strength relationship to below-ground measurements of golf putting green. by Shehbaz Singh, MS

Shear strength is generally referred to as the rotational traction force required to break the turf. Shear strength testing is commonly done for the sports field to better understand player-surface interaction. In the game of golf, surface strength has been used to estimate the ball mark severity on greens. USGA agronomists have begun to measure surface strength to develop a better understanding of its role in putting green performance. However, shear strengths' relationship to other turf growth and playability characteristics largely remain unknown.

In 2023, a study was conducted on putting greens to understand the shear strength relationship with above-ground and below-ground measurements of golf greens at the Bob Berry Sunshine Course, Lemont, IL.

Objectives

  • Evaluate the relationship of turfgrass shear strength versus turfgrass health measures both above and belowground.
  • Evaluate shear strength as a predictor of turfgrass health prior to or during stress.

Greens Description

There are a total of four creeping bentgrass greens which includes one large practice green at the Bob Berry Sunshine Course in Lemont. During the 2020 renovation, ‘L-93’ plus ‘Penn G-2’ on greens 1, 2, and 3 was killed. Each was then reseeded with newer creeping bentgrass varieties of ‘Pure Distinction’, ‘007’ and ‘PC 2.0’. The practice green was completely rebuilt as a variable depth green with one half seeded with ‘Penn A-1’ plus ‘Penn A-4’ and the other half with ‘777’.

Table 1. Putting greens and description at Bob Berry Sunshine Course, Lemont, IL.
Image 1. Aerial view of putting greens at Bob Berry Sunshine Course, Lemont, IL.

Greens Evaluation Methodology

• Each green was divided into front, middle, and back sections.

• One point was marked in front, middle, and back sections of each green in a straight line.

• Four data samples were systematically collected around each point monthly from April to October during 2023.

Image 2. Evaluation Methodology: Aerial view of green 1 using SpecConnect software, Spectrum Technologies, Inc., Bob Berry Sunshine Course, Lemont, IL.

Data

Turfgrass Quality — 1–9 scale, with 6 acceptable and 9 best

Normalized Difference Vegetation Index (NDVI) — Greenskeeper/Trimble HCS-100

Soil Moisture (%) — 1.5-inch depth TDR 350, Spectrum Technologies Inc.

Shear Strength (Nm) — Shear-strength tester, Turf-Tec International

Surface Hardness — TruFirm meter, Spectrum Technologies Inc. IL

Ball Roll (ft) — Stimpmeter, USGA

Root Length (inch) — Maximum root length using a standard 0.5-inch diameter soil core

Organic Matter Accumulation (inch) — Maximum OM accumulation using 0.5-inch diameter soil sampler

  • Nematode Population Density (per 100 cc soil) — Plant parasitic nematodes were extracted using a modified sucrose flotation technique. Soil samples were same cores used for root length measurement

Below-ground Measurement Data

Shear Strength: Trends showed lower shear strength values for all creeping bentgrass greens during the spring months (Apr, May). This corresponds to the slow growth of creeping bentgrass during the spring season in the Chicago area. Higher shear strength values were observed for all greens during the summer months (Jun, Jul) when bentgrass is growing at its full potential. Shear strength values decreased during the early fall months (Aug, Sep).

On the variable depth creeping bentgrass green, trends showed newer ‘777’ with higher shear strength values on most rating dates, while older ‘Penn A-1’ plus ‘Penn A4’ had lower shear strength values.

Figure 1. Shear strength (Nm) of creeping bentgrass putting greens from Apr 2023 to Sep 2023, Bob Berry Sunshine Course, Lemont, IL.
Figure 2. Soil moisture of creeping bentgrass putting greens from Apr 2023 to Sep 2023, Bob Berry Sunshine Course, Lemont, IL.

Root Length: Trends showed greater root length in the practice green creeping bentgrass which had a newly built variable depth rootzone. In contrast, the root length for the three older USGA spec greens were relatively shorter during all months rated in 2023. Maximum root length was greatest in the front section of most putting greens and this is where soil moisture was relatively higher.

Figure 3. Maximum root length of creeping bentgrass putting greens from Apr 2023 to Sep 2023, Bob Berry Sunshine Course, Lemont, IL.

Organic Matter Accumulation: The soil cores were measured for organic matter accumulation. Organic matter accumulation depth for greens ranged from 0.52 to 0.88 inch. Organic matter accumulation for bentgrass greens increased from the summer months to the fall months.

Figure 4. Organic Matter Accumulation of creeping bentgrass putting greens from Apr 2023 to Sep 2023, Bob Berry Sunshine Course, Lemont, IL.

Total Plant Parasitic Nematode Population: Root-knot (Meloidogyne), stubby root (Nanidorus), ring (Mesocriconema), and a smaller number of lance (Hoplolaimus) nematodes were present in all greens for at least one rating date during 2023. Overall, a higher nematode populations were observed for greens 1, 2, and 3 which were 20 year old USGA spec construction. As expected, nematode populations were generally absent in the new 3-year-old variable depth practice green. In the USGA spec greens, with regard to population densities, ring nematodes predominated and root-knot nematodes were intermediate and stubby root nematodes were least observed and lance nematodes were infrequently found.

Correlation Analysis Greens 1, 2, and 3 (20-year-old greens) Correlations ranked from highest to lowest

  • Organic Matter. Very strong positive correlation between shear strength and organic matter accumulation with ‘r’ value of 0.80.
  • Root Length. Strong positive correlation between shear strength and root length with ‘r’ value of 0.63.
  • Nematodes. A moderate negative correlation between shear strength and nematode population was observed with ‘r’ value of -0.57.
  • Soil Moisture. Correlation analysis revealed a weak positive correlation between shear strength and soil moisture with a correlation coefficient ‘r’ of 0.38.
Table 2. Correlation analysis of below-ground measurements with shear strength. Using the average data of each measurement over the 2023 season (Apr-Sep). The number value stands for the coefficient of correlation ‘r’ which ranges from -1 to 1. ‘r2’ stands for the coefficient of determination which ranges from 0 to 1.

Correlation Analysis Practice Putting Green (3-year -old) Correlations ranked from highest to lowest

  • Organic Matter. A very strong negative correlation between shear strength and organic matter accumulation with ‘r’ value of -0.84.
  • Soil Moisture. A strong positive correlation between shear strength and soil moisture with a correlation coefficient ‘r’ of 0.64.
  • Nematodes. A strong positive correlation between shear strength and total nematode populations was observed with ‘r’ value of 0.62.
  • Root Length. A weak negative correlation between shear strength and root length with ‘r’ value of -0.23.
Table 3. Correlation analysis of below-ground measurements with shear strength. Using the average data of each measurement over the 2023 season (Apr-Sep). The number value stands for the coefficient of correlation ‘r’ which ranges from -1 to 1. ‘r2’ stands for the coefficient of determination which ranges from 0 to 1.

Final Image

‘Little Gem’ Magnolia is a favorite small tree in the southeastern United States. Settle, May 15, 2024

“Magnolia is an ancient genus that appeared before bees evolved. They are theorized to have evolved to encourage pollination by beetles instead. Fossilized specimens of M. acuminata have been found dating to 20 million years ago, and fossils of plants identifiably belonging to the Magnoliaceae date to 95 million years ago.” For more see Magnolia on Wikipedia here.

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CDGATurfgrassProgram

Written by Derek Settle, PhD & Shehbaz Singh, MS. Mission: Provide science-based turfgrass research and diagnostics to 400+ member golf courses/superintendents.