Nice Weather! Cooler, Brown Patch, Dollar Spot, 1st Rust, and Tee Research

CDGATurfgrassProgram
7 min readAug 11, 2023

As we near mid-August we continue to enjoy a period without severe thunderstorms. In northern Illinois, early August has provided near perfect outdoor conditions. We are past summer’s peak heat and for the first time it has begun to feel like fall. It also means longer periods of heavy dew at night and an increase in signs of turfgrass wear (accumulates in the usual high traffic areas). This all brings a subtle shift of awareness for turfgrass managers. Part of that shift, in the fall, is that our scouting for diseases increases both aboveground (e.g., dollar spot driven by extended periods of leaf wetness) and belowground (e.g., summer patch of bluegrasses driven, in part, by the accumulation of traffic and thus soil compaction).

Image 1. Conditions are beginning to look more and more like fall. A creeping bentgrass/annual bluegrass fairway sees greater disease pressure (dollar spot) given longer periods of leaf wetness (heavy dew) in August. Settle, Aug 11, 2023

And in the landscape, the month of August is performing like a ballet. Following a shaky start (drought) we then shifted to a record wet (July). In the end growing season 2023 turned out okay. Right now, Northern Illinois continues a Swan Lake of green that has been going on for about a month (lush grass and the plethora of annuals and perennials in peak bloom). Conditions in central Illinois have also taken a turn for the better — August thunderstorms with large amounts of rain targeted midstate like a bull’s eye. And the timing couldn’t have been better. Late summer is also a time when course conditions typically reach their prime. The presence of deep roots combine with drier weather patterns — typical of fall in the upper Midwest. It provides superintendents greater control as irrigation systems are dialed-in to provide optimum levels of soil moisture. Let’s see what the rest of August brings, but the 10 day forecast is about as good as it gets.

Weather

Figure 1. Current air and soil temperatures. Highs have moderated in August. Bob Berry Sunshine Course, Lemont, IL
Figure 2. Recent precipitation in early August helped to replenish rainfall deficits in central and southern Illinois.
Figure 3. Current drought conditions in the United States. For Illinois drought conditions have improved versus early summer. D0 = Abnormally Dry; D1 = Moderate Drought; D2 = Severe Drought; D3 = Extreme Drought

Brown Patch, Rhizoctonia solani

Current research (creeping bentgrass tee at North Shore Country Club in Glenview) and scouting (RTF tall fescue tee at Bob Berry Sunshine Course) indicates that peak brown patch activity just occurred during the first two weeks in August. Environmental conditions were conducive: Nights in the upper 60s and a leaf wetness duration of 10 hours or more.

Figure 1. Research: Brown patch disease progression in 4 ft x 6 ft untreated plots (mean of 4 replicates) on a creeping bentgrass practice tee, North Shore Country Club, Glenview, IL.
Image 1. Research: A creeping bentgrass practice tee with a history of brown patch development. Individual rectangular treatment plots, 4 ft by 6 ft, are indicated by a red dot on each corner. This study (RCBD, 9 treatments, replicated 4 times) investigates the curative control of fungicides with and without an adjuvant called Sync (Precision Labs). North Shore Country Club, Glenview, IL. Settle Aug 9, 2023
Image 2. Research: Close up of brown patch (Rhizoctonia solani) in an untreated plot on a creeping bentgrass practice tee, North Shore Country Club, Glenview, IL. Settle Aug 9, 2023
Image 3. Scouting: In a week, rapid brown patch development is observed on the back portion of a RTF tall fescue tee, Bob Berry Sunshine Course, Lemont, IL. Settle Aug 8, 2023
Image 4. Scouting: Brown patch blight of approximately 80% (rapid disease progression in 7 days) is observed on the front portion of a RTF tall fescue tee, Bob Berry Sunshine Course, Lemont, IL. Settle Aug 8, 2023

Dollar Spot, Clarireedia jacksonii

Dollar spot also has finally taken off like a rocket. Conditions that are conducive for brown patch in summer also promote dollar spot. Primarily we are talking about leaf wetness of 10 hours or more.

Unlike brown patch, dollar spot activity will continue as long as nighttime temperatures remain above 50 degrees. In other words, dollar spot will likely continue to be a significant problem for the next three months of August, September and October.

Select Turfgrass Species Susceptible to Dollar Spot — Both cool season (C3) and warm season (C4)

  1. Can be highly susceptible. Creeping bentgrass (C3), annual bluegrass (C3), Kentucky bluegrass (C3), seashore paspalum (C4)
  2. Often shows good resistance. Tall fescue (C3), bermudagrass (C4), zoysiagrass (C4)
Figure 1. Research: Brown patch disease progression in 4 ft x 6 ft untreated plots (mean of 4 replicates) on a creeping bentgrass practice tee, North Shore Country Club, Glenview, IL.
Image 1. Research: A creeping bentgrass practice tee with a history of dollar spot development. Individual rectangular treatment plots, 4 ft by 6 ft, are indicated by a red dot on each corner. This study (RCBD, 9 treatments, replicated 4 times) investigates the curative control of fungicides with and without an adjuvant called Sync (Precision Labs). North Shore Country Club, Glenview, IL. Settle Aug 9, 2023
Image 2. Research: Close up of dollar spot (Clarireedia jacksonii) in an untreated plot on a creeping bentgrass practice tee, North Shore Country Club, Glenview, IL. Settle Aug 9, 2023
Image 3. Scouting: Dollar spot in a Kentucky bluegrass rough area (mound) at Bob Berry Sunshine Course, Lemont, IL. Settle, Aug 8, 2023.
Image 4. Scouting: A bleached white hourglass lesion can be used to help diagnose dollar spot at higher heights of cut (a Kentucky bluegrass rough), Bob Berry Sunshine Course, Lemont, IL. Settle, Aug 8, 2023

First Report of Stem Rust, Puccinia graminis

Another sign of fall you ask? Rust has begun on Kentucky bluegrass lawns as of this week. I spotted off-color thinning areas and took a closer look. And there it was, the yellow to orange uredinia. How rust gets its name.

Control

Best control starts at establishment. Use newer varieties of Kentucky bluegrass. If using sod, find out what single variety or varieties (the blend) you are purchasing. You want to make sure all varieties used have been selected for resistance to rust and other important diseases. Kentucky bluegrass has a few.

For more information see the National Turfgrass Evaluation Program website and look for a test site nearest your location. Please see below.

Image 1. Scouting: Rust negatively impacting Kentucky bluegrass, but not touching the smooth crabgrass in a lawn, Evanston, IL. Settle, Aug 11, 2023
Image 2. Scouting: Closeup of rust negatively impacting Kentucky bluegrass, but not touching smooth crabgrass in a lawn, Evanston, IL. Settle, Aug 11, 2023

Tee Research — August 11, 2023 by Shehbaz Singh, MS

As a part of monthly evaluation of greens, fairways, and tees at Bob Berry Sunshine Course, all tees were evaluated last week.

Background. All tees at the Bob Berry Sunshine Course in Lemont were seeded with different type of turfgrass species/varieties during 2020 renovation project by the Wadsworth Golf Construction Company based in Plainfield, IL. Before renovation, all tees were creeping bentgrass. The tees are currently in their third year of establishment after renovation. Surfaces consist of five turfgrass species that include; creeping bentgrass, colonial bentgrass, Kentucky bluegrass, perennial ryegrass and tall fescue.

Data Collection. As before, data was collected in three parallel lines on the tee surface. Readings then the averaged across each of the three lines. The following four parameters were evaluated.

1. Turfgrass Quality (1–9, 6 acceptable and 9 best)

2. Normalized Difference Vegetation Index, GreenSeeker by Trimble

3. Weed Contamination (%)

4. Turfgrass Density (%)

5. Localized Dry Spots (%)

6. Root length (in) Maxiumum root length was measured taking the average of four 0.5-inch diameter soil samples. On each tee, four evaluation or sampling points were selected in a systematic way (four corner points of 10-ft width square in center of tee). All future investigations are conducted in the close proximity to selected points on the tee.

7. Nematodes (number per 100 grams soil) Root-feeding nematodes are identified and enumerated after extracting from the soil by lite sucrose and centrifugation.

HD Sport 2 Kentucky Bluegrass Tee (soil-based root zone)

  1. Data: Quality 6.0, NDVI 0.63, Contamination (63.3% mainly creeping bentgrass), Density 80+%, LDS 13.3%, and Root Length 6 in.
  2. Notes: Acceptable visual quality, but lower than July. High bentgrass contamination, and more than 10% localized dry spot.

HGT Kentucky Bluegrass Tee (soil-based root zone)

  1. Data: Quality 5.6, NDVI 0.64, Contamination (71% mainly creeping bentgrass), Density 90%, LDS 15%, and Root Length 7.4 in.
  2. Notes: Visual quality not acceptable, high contamination, and prone to localized dry spot.

RTF Tall Fescue Tee

  1. Data: Tee C (sand and soil-based root zone) Quality 5.6, NDVI 0.65, Contamination (48.3% mainly bentgrass), Density +90%, LDS 6%, and Root Length 7.5 in.
  2. Data: Tee H (soil-based root zone): Quality 6.0, NDVI 0.64, contamination (10 % mainly Poa annua), +95% turf density, and root length 7.2 in.
  3. Notes: Tall fescue had deeper roots and less localized dry spots. Tee H was negatively impacted by brown patch.

Penncross 2.0 Creeping Bentgrass Tee (sand and soil-based root zone)

  1. Data: Quality 4.6, NDVI 0.63, Contamination 5% (Poa annua), Density 75%, LDS 21.6%, and Root Length 7.6 in.
  2. Notes: Localized dry spot areas but contamination is minimal. Root length improved compared to July.

Musket Colonial Bentgrass Tee (sand and soil-based root zone)

  1. Data: Quality 4.0, NDVI 0.54, Contamination 26.6% (creeping bentgrass), Density 65%, LDS 21.6%, and Root Length 3.8 in.
  2. Notes: Had lowest turf density among all other tees due to its bunch type growth habit. High localized dry spot incidence.

Piranha Creeping Bentgrass Tee (sand and soil-based root zone)

  1. Data: Quality 5.0, NDVI 0.62, contamination 5% (Poa annua), Density 90%, LDS 15%, and Root Length 7 in.
  2. Notes: Not visually acceptable. More than 10% localized dry spot.

Flagstick Creeping Bentgrass Tee (sand and soil-based root zone)

  1. Data: Quality 4.6, NDVI 0.53, Contamination (5.2% Poa annua), Density 65 %, LDS 31.6%, and Root Length 6.5 in.
  2. Notes: Not visually acceptable and poor turf density. Had most localized dry spot compared to all other tees.

RPR Perennial Ryegrass Tee (soil-based root zone)

  1. Data: Quality 7.0, NDVI 0.73, Contamination 10.3%, Density 78.8%, LDS 0%, and Root Length 5.2.
  2. Notes: This tee showed great improvement in quality and NDVI because of N fertilizer. Fertilization was done 2 weeks ago for an ongoing Pythium blight disease study on this tee.
Figure 1. Visual quality of tees at Bob Berry Sunshine Course, Lemont, IL. Aug 9, 2023
Figure 2. NDVI of tees at Bob Berry Sunshine Course, Lemont, IL. Aug 9, 2023
Figure 3. Contamination of tees (primarily by creeping bentgrass and/or Poa annua) at Bob Berry Sunshine Course, Lemont, IL. Aug 9, 2023
Figure 4. Localized dry spot of tees (primarily by creeping bentgrass and/or Poa annua) at Bob Berry Sunshine Course, Lemont, IL. Aug 9, 2023
Figure 5. Maximum root length of tees at Bob Berry Sunshine Course, Lemont, IL. Aug 8, 2023
Figure 6. Sheer strength of tees at Bob Berry Sunshine Course, Lemont, IL. Aug 8, 2023
Figure 7. Root knot nematodes extracted from tees at Bob Berry Sunshine Course, Lemont, IL. Aug 9, 2023
Figure 8. Ring nematodes extracted from tees at Bob Berry Sunshine Course, Lemont, IL. Aug 9, 2023
Figure 9. Spiral nematodes extracted from tees at Bob Berry Sunshine Course, Lemont, IL. Aug 9, 2023

Final Photo

Luna hibiscus is part of a group called hardy hibiscus, Hibiscus moscheutos. These are warm-season deciduous perennials that are cold tolerant. Flowers impress because they are about the size of a dinner plate. For more unusual and interesting information on Hibiscus see Wikipedia. Settle, Aug 11, 2023.

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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.