October Arrives! Chilly Low Temps, Dollar Spot Research Ends, Broadleaf Weeds, and Fairway Data

As October begins, the air temps tell us it is now fall without a doubt. Cool temperatures are consistently upon us with nighttime lows dipping into the 40s. In September we were relatively dry and would experience a day or two each week which felt like summer. It was a fantastic month if your course was investing time and resources on improvements or as a golf course superintendent might say, “We are busy working on projects.”. Those projects are key to bringing golf courses forward in a technological way that is not trivial. Several golf courses in Chicago and the Midwest date their origin to the turn of the century — so much was very different then.

Image 1. A red maple with fall color drops its leaves unbeknownst to golfers who play nearby on a green, Village Greens of Woodridge, Woodridge, IL. Settle, Sep 27, 2022

For example, projects allow the latest revolution, like sand bunker construction, to happen. Projects shine a bright light on our newest varieties of turfgrass. Especially those improved for use on tees, fairways and greens. And boy have they advanced in just a decade. For example, creeping bentgrass has the best disease resistance to date versus dollar spot. Nearly all projects result in better playing conditions for the game of golf and, best of all, a majority will allow for reduced inputs in the near future. During October, the pace turfgrass establishment will naturally slow. Until then may the projects, and good weather, continue uninterrupted.

Weather

North Shore CC, Glenview. North Chicago Suburbs: After higher temperatures last week, Chicago finally saw more typical fall weather. Air temperatures ranged from 40 to 70.3°F over the last seven days. Maximum temperatures ranged from 60.5 to 70.3°F. Minimum temperatures ranged from 40 to 52.3°F. Relative humidity during the week was mostly lower than 80%. Rainfall was experienced on the weekend of Sep 24–25 and cumulative rainfall was 0.32 inches over the last seven days.

Bob Berry Sunshine Course, Lemont. Air temperatures in the south Chicago suburbs had a greater range of 35 to 73.6°F over the last seven days. Maximum air temperatures ranged from 61.7 to 73.6°F. Minimum air temperatures ranged from 35 to 52.3°F. The relative humidity ranged from 71 to 84% over the evaluated period. Cumulative rainfall was 0.01 inches over the last seven days. Conditions were dry.

Figure 1. Air temperature, humidity and rainfall during September, 2022.

Dollar Spot Research Ends

Nighttime lows are now suppressing the development of the fungal disease dollar spot, Clarireedia jacksonii. For a period lasting approximately 6 weeks, from late summer into fall, high dollar spot disease pressure was experienced. This is typical for the cool, humid environment of Chicago. Large accumulations of leaf wetness in the form of dew and plant-produced guttation naturally occur at this time. Dollar spot represents the most significant disease of golf courses in regions were creeping bentgrass is extensively used. Creeping bentgrass is highly susceptible.

Image 1. And with that, a solid tine aerification event, a dollar spot study ends in number 8 fairway, North Shore Country Club, Glenview, IL. Settle, Sep 26, 2022

Materials and Methods

A study with 17 fungicide treatments began May 23 and ended Sep 26, 2022. The experimental design used small plots (4 ft by 6 ft) arranged in a randomized complete block design with 4 replicates. A CO2-powered back pack sprayer with flat fan nozzles made applications. Data collection was weekly.

Visual Quality Data

If you look at visual quality you can appreciate how much dollar spot occurred at the end of the season. To help simplify the summary it is often helpful to look at application intervals as this greatly impacts fungicide efficacy. Shorter application intervals favoring better control of dollar spot. Fungicides were applied at labeled rates.

Every 14 days

All treatments applied at a 14 day interval provided acceptable visual quality during peak dollar spot pressure (Figure 1). The rating scale is 1–9, with 9 best and 6 representing the minimum required for acceptable quality. Note: a 6.0 visual quality rating equated to dollar spot disease of 10% or less.

Figure 1. Fungicide treatments applied every 14 days in a L-93 creeping bentgrass fairway, North Shore Country Club, Glenview, IL.

Every 21 days

About half the treatments applied at a 21 day interval provided acceptable visual quality during peak dollar spot pressure. Only those that maintained acceptable quality are shown (Figure 2). The rating scale is 1–9, with 9 best and 6 representing the minimum required for acceptable quality. Note: a 6.0 visual quality rating equated to dollar spot disease of 10% or less.

Figure 2. Select fungicide treatments applied every 21 days in a L-93 creeping bentgrass fairway, North Shore Country Club, Glenview, IL.

Every 28 days

None of the treatments applied at a 28 day interval provided acceptable visual quality during peak dollar spot pressure(Figure 3). The rating scale is 1–9, with 9 best and 6 representing the minimum required for acceptable quality. Note: a 6.0 visual quality rating equated to dollar spot disease of 10% or less.

Figure 3. Fungicide treatments applied every 28 days in a L-93 creeping bentgrass fairway, North Shore Country Club, Glenview, IL.

Fall Weeds

It is in the fall that we learn an important lesson about the “right plant in the wrong place”. That would be weeds that we consider undesirable. In the realm of golf courses our primary need is to have all areas in play as weed-free as possible. It has practical implications for the game of golf. Weeds on tees, fairways and/or greens can interrupt uniform conditions of playing surfaces. Ball roll on green in particular would be a problem. But we can also say the same is true for fairways and tees. Roughs, well not so much.

Fall, in particular, plays a special role in broadleaf weed control. It is in fall that plants become easier to control. That may sound like a blanket statement and, well, it is. Here’s why. Prior to winter dormancy, all plants relocate beneficial carbohydrates and other stuff below ground to their storage organs — roots, stolons, rhizomes, tubers, bulbs, etc. This means greater efficacy by herbicides to selectively remove weeds from turfgrass can and does take place in the fall. It means fewer applications are necessary. It means one instead of two applications (what we typically see in the spring for difficult-to-control weeds). October is a key month to take advantage of a single application for weed control. Always follow the manufactures label when using pesticides.

Image 1. A combination of legumes (black medic and white clover) find their way into the front of a Crystal Bluelinks creeping bentgrass fairway at Bob Berry Sunshine Course in Lemont, IL. Settle, Sep 27, 2022
Image 2. A close up of white clover in bloom persisting at 0.5 inch mowing height in a Crystal Bluelinks creepin bentgrass fairway, Bob Berry Sunshine Course, Lemont, IL. Settle, Sep 27, 2022

Fairway Fall Research Update by Shehbaz Singh, MS

Last week I took data to investigate fairways at Bob Berry Sunshine Course in Lemont. All fairways are seeded with newer creeping bentgrass cultivars. An apron to a large practice putting green serves as a check; older cultivar of Penn A1 plus Penn A4.

Objective. Evaluate quality of creeping bentgrass cultivars used as fairways in the fall and record any issues present. For example, low levels of weed contamination, localized dry spot and scalping were previously documented.

Materials and Methods. Evaluation of fairways was done as before in summer. Briefly, data included visual quality, Normalized Difference Vegetation Index or NDVI using the handheld GreenSeeker (Trimble Inc.) and visual estimation (%) of any problematic issues (weeds and localized dry spot). In order to do a systematic investigation, data was collected in three parallel lines (3 data points per line for a total of 9 data points) within each fairway section of front, middle, and back. From a spatial perspective, the front fairway section is near the approach of each green.

Quality Results. Trends of quality differences were observed within each fairway among front, middle, and back sections.

  • Creeping Bentgrass 1 Fairway Crystal Bluelinks saw good visual quality and NDVI ratings.
  • Creeping Bentgrass 2 Fairway OO7 saw excellent overall visual quality and NDVI ratings.
  • Creeping Bentgrass 3 Fairway Pure Select saw excellent overall ratings except in the front section.
  • Creeping Bentgrass Apron Penn A1 plus Penn A4 saw visual good overall ratings except in the front section.

Quality Conclusions. Overall, fairway quality was the best in the front sections (near approach of each green) for Crystal Bluelinks and OO7. This was not true for Pure Select and the Penn A1/Penn A4 blend due to problematic issues of weed infestation (Pure Select) and scalping (Penn A1/Penn A4).

Figure 1. Quality data for creeping bentgrass areas (front, middle, back) at Bob Berry Sunshine Course, Lemont, IL

Weeds. Trends of differences were observed within each fairway among front, middle, and back sections.

  • Creeping Bentgrass 1 Fairway Crystal Bluelinks had the most infestation of weeds. Primary weeds were black medic and white clover. The high weed infestation could be due to a high soil moisture content which is seen in 1 fairway. Also, Crystal Bluelinks appeared less dense relative to OO7 and Pure Select.
  • Creeping Bentgrass 2 Fairway OO7 saw low levels of weed infestation and was only present in the back section of fairway. The primary weed observed was smooth crabgrass.
  • Creeping Bentgrass 3 Fairway Pure Select saw low levels of weed infestation, interestingly most occurred in the front fairway section. Black medic was the primary weed. Also, scalp injury was higher in Pure Select versus Crystal Bluelinks and OO7.
  • Creeping Bentgrass Apron Penn A1 plus Penn A4 saw minor weed infestation while the scalp injury was quite higher. Black medic was the primary weed. Scalp injury was localized in the front and back sections where mower turns occur. Scalp injury could also be due to cultivar.
Figure 2. Scouting and mapping of weed infestations in fairway sections can be used to improve future applications of herbicides.

Localized Dry Spot. Trends of differences were observed within each fairway among front, middle, and back sections.

  • Creeping Bentgrass 1 Fairway Crystal Bluelinks saw trace levels of localized dry spot. The lowest among all fairways.
  • Creeping Bentgrass 2 Fairway OO7 saw moderate levels of localized dry spot. The most among all fairways.
  • Creeping Bentgrass 3 Fairway Pure Select saw low levels of localized dry spot.
  • Creeping Bentgrass Apron Penn A1 plus Penn A4 saw moderate levels of localized dry spot in the front, middle, and back sections. It was estimated at 4.2%, 1.2%, and 8.5% respectively.
Figure 3. Scouting and mapping of localized dry spots in fairway sections can be used to improve the future scheduling of irrigation.

Final Photo

It’s the ‘end of the line’ for a grassy weed (smooth crabgrass or Digitaria ischaemum) in a fine fescue lawn. Low temperatures in the 40s has put the hurt on this warm-season (C4) annual grass. Settle, Sep 30, 2022

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CDGATurfgrassProgram

Dedicated researchers and turf pathologists working for golf course superintendents in the Chicago area.