Localized Flooding! Unusually Cool, Leaf Spot, Broadleaf Weeds Surge, and Tee Research

CDGATurfgrassProgram
5 min readJul 14, 2023

It’s been a rough week weather-wise (severe thunderstorms), but otherwise we have good news. Dry conditions have largely disappeared and rapid turfgrass recovery has been experienced. Regular rain events are now the norm in summer 2023 — though it’s meant flooding for some. And then some tornado sirens on Wednesday, July 12 — never good and severe damage of 60–70 trees was reported by one Chicago course. Overall, this growing season has advanced in fits and spurts. Three distinct phases so far, but who’s counting? 1) Overly Cool: During spring, a dry April surprised us with overly cool temperatures which effectively halted normal growth of creeping bentgrass. 2) Very Dry: Summer began with conditions of severe drought for a majority of Illinois. 3) Big Rains: In early July, the first deluge of heavy rain was experienced in northern Illinois with flash floods since.

Image 1. Conditions of near perfect growing conditions for cool season turfgrass are now in place in Northern Illinois and Chicago. Hinsdale Golf Club, Clarendon Hills, IL. Settle, Jul 11, 2023

Near constant rain has meant signs of fungi (mushrooms) are everywhere. In the landscape, just like that, browns have quickly faded/disappeared. Daylilies, Hemerocallis, are now seeing peak bloom. In similar fashion, turfgrass is growing fast and looking lush. Given the drought we’ve just experienced, such rapid recovery has been jaw-dropping. Best of all, most of us get to enjoy it with minimal effort. Take Home Message: From lawns to golf courses things have greatly improved. It’s what the summer season can (but doesn’t always) bring the outdoors. So go out and enjoy the game of golf during near optimal conditions via a cool July. Be amazed at nature’s resiliency (given rain) and appreciate the efforts of those who maintain.

Weather

Figure 1. A 14-day precipitation map tells the story of a sudden change of conditions. Current rainfall totals are several times normal (up to 400% greater) in northern Illinois. Courtesy NOAA
Figure 2. 2022 vs 2023 = Very Different Conditions. Map of the Midwest with comparison of July, 2022 (one year ago) versus July, 2023. In Illinois, conditions of Moderate Drought (D1 = beige) to Severe Drought (D2=orange) predominate the entire state. For more see U.S. Drought Monitor
Figure 3. Plentiful rainfall with unusually cool temperatures in July have allowed for rapid cool season turfgrass growth and recovery, Bob Berry Sunshine Course, Lemont, IL.

Report of Leaf Spot of Creeping Bentgrass

Leaf spots are normally associated with cool conditions of the spring and fall seasons. However, midsummer 2023 has been a bit abnormal temperature-wise. We are currently experiencing night temperatures which are unusually cool for mid July. Ranging from 50s to 60s with high humidity and frequent rains. Multiple fungicides are labeled for leaf spot and offer good control. Be aware that leaf spot pathogens have been associated with fungicide resistance. A good example of why it's necessary to rotate different modes of action with regard to fungicide programs.

Image 1. A OO7 creeping bentgrass green with initial spotty damage that progressed to small bronze to red patches. Damage associated with cool, wet conditions during early July. Settle, Jul 10, 2023
Image 2. A OO7 creeping bentgrass sample with both healthy and unhealthy (discolored) leaf blades. Settle, Jul 10, 2023
Image 3. Confirming a leaf spot fungal pathogen is associated with symptoms. Possibly Bipolaris or Exserohilum. Settle, Jul 10, 2023

Featured Weed: White Clover, Trifolium repens

Did you notice? One broadleaf weed is now shining (flowering) above the rest. It is white clover. As a legume, clover can fix its own nitrogen and this unique advantage makes it competitive across a broad range of environments, soil types and turfgrass species.

We are seeing more white clover this summer. It probably has to do with the drought just experienced (May and June). The dormant turfgrass areas were not as competitive versus white clover. White clover continued to grow relatively unfazed. Just about as bullet proof a plant as it gets.

Research has looked at mixed stands of clover and turf. A recent example found is by Bigelow et al., International Turfgrass Society Research Journal, 2020. Cool-season lawn performance as influenced by ‘Microclover’ inclusion and supplemental nitrogen

Image 1. A Kentucky bluegrass rough recovers from conditions of severe drought. White clover remains relatively unfazed and is currently out-growing the turfgrass. Bob Berry Sunshine Course, Lemont, IL. Settle Jul 13, 2023
Image 2. Closeup of white clover, Trifolium repens. Bob Berry Sunshine Course, Lemont, IL. Settle Jul 13, 2023

Tee Research — July 12, 2023 by Shehbaz Singh, MS

All tees were evaluated this week — part of a monthly scientific evaluation of greens, fairways, and tees at Bob Berry Sunshine Course in Lemont, IL.

Investigations evaluate playability, agronomic characteristics and quality. 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.* *Tees were renovated in 2020 by Wadsworth Golf Construction Company.

Evaluation Procedure

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

1. Visual Quality (1–9 scale with 9 best and 6 = minimum acceptable)

2. Normalized Difference Vegetation Index (NDVI) was measured using GreenSeeker by Trimble.

3. Weeds (%) were visually estimated around each point in about area of a 5 ft radius circle.

4. Localized Dry Spot (%) was visually estimated around each point in about area of 5 feet radius circle.

Additionally, four sampling points were selected (four corner points of a 10 ft square in the center of each tee). Any future investigations on (parameters 5–8) each tee will be conducted in the close proximity of selected points on the tee.

5. Root length (in) was measured taking the average of four 0.5 inch diameter soil samples (maximum root length).

6. Thatch (in) was measured taking the average of four 0.5 inch diameter soil samples.

7. Shear Strength was measured using Shear Strength Tester by Turf-Tech International Inc.

8. Root Length (in) was measured as the average of four 0.5 inch diameter soil samples (maximum root length).

9. Root-Feeding Nematodes (number per 100 g soil) were extracted by lite sucrose centrifugation (upper 2 inches of four soil cores).

Figure 1. Visual quality trends are not directly associated with creeping bentgrass cultivar. Rather, greatest influence was the soil type. Only Penncross is located on a soil-based tee, whereas the other newer varieties are all located on sand-capped tees. Tees with sand suffered more localized dry spot from a lack of rainfall experience during May and June. Bob Berry Sunshine Course, Lemont, IL
Figure 2. As was seen in visual quality data, NDVI trends are not directly associated with creeping bentgrass cultivar. Rather, greatest influence was the soil type. Only Penncross is located on a soil-based tee, whereas the other newer varieties are all located on sand-capped tees. Tees with sand suffered more localized dry spot from a lack of rainfall experience during May and June. Bob Berry Sunshine Course, Lemont, IL
Figure 3. Visual quality of tees ranged from 4 to 7 on July 12, 2023. Most tees showed acceptable visual quality except a majority of creeeping bentgrass tees whichsuffered from overly dry growing conditions in May and June. Bob Berry Sunshine Course, Lemont, IL
Figure 4. NDVI of tees ranged from 0.56 to 0.73 on July 12, 2023. RTF tall fescue recorded the highest NDVI reading in July month whereas RPR perennial ryegrass tee had the lowest reading. The electronic reflectance values nicely matched the trends of visual quality ratings. Bob Berry Sunshine Course, Lemont, IL
Figure 5. Contamination of tees by other turfgrass species on July 12, 2023. Kentucky Bluegrass tees had most contamination ranging from 61.7 to 66.7% and was caused by creeping bentgrass. RTF tall fescue Tee C had 53.3% creeping bentgrass contamination while RTF tall fescue Tee H had 16.7% creeping bentgrass contamination. Creeping bentgrass tees saw least contamination mainly from Poa annua (1.7-20%). Musket colonial bentgrass also had creeping bentgrass contamination of 30%. RPR perennial ryegrass had 36.7% Poa annua contamination. Bob Berry Sunshine Course, Lemont, IL
Figure 6. Localized dry spot (%) on tees. Rainfall during July has greatly reduced LDS on all tees. Last month (June) tees saw LDS of 1-20%. Bob Berry Sunshine Course, Lemont, IL
Figure 7. Maximum root length (inches) of tees. RTF tall fescue had deepest roots of about 6.5 inches. Colonial bentgrass and perennial ryegrass tee had shortest roots. Little improvement in the root length of bentgrass tees were noticed in comparison to last months root length data. Bob Berry Sunshine Course, Lemont, IL
Figure 8. Figure 8. Thatch accumulation (inches) of tees. Highest thatch accumulation was observed for creeping bentgrass tees and ranged from 0.8 to 1.5 in. Kentucky bluegrass had about 1 to 1.2 in. However, RTF tall fescue had less and ranged from 0.65 to 0.8 in. Musket colonial bentgrass and RPR perennial ryegrass had lowest thatch depth, likely due to their lack of lateral growth (both are bunchgrasses).
Figure 9. Soil moisture of tees. In July, soil moisture is now higher than previous months and ranged from 25.4 to 43.1% due to frequent rain. In June, soil moisture was 20.4 to 39.1%. Bob Berry Sunshine Course, Lemont, IL
Figure 10. Shear strength (Nm) of tees. Musket colonial bentgrass tee had unacceptable shear strength (< 10 Nm). Bob Berry Sunshine Course, Lemont, IL
Figure 11. Ring nematodes across tees of different turfgrass species. This was the most common nematode found and population densities have increased from May to June. Bob Berry Sunshine Course, Lemont, IL, Jul 12, 2023
Figure 13. Spiral nematodes across tees of different turfgrass species. This nematode was most often associated with soil-based tees, Bob Berry Sunshine Course, Lemont, IL. Jul 12, 2023

Final Photos

Many colorful varieties of Hemerocallis (or daylily) are now in bloom. Midwest Golf House, Lemont, IL. Settle Jul 13, 2023. Daylilies are an example of name changing — taxonomy at work. “Despite the name, daylilies are not true lilies, although the flower has a similar shape. Before 2009, the scientific classification of daylilies put them into the family Liliaceae. In 2009, under the APG III system, daylilies were removed from the family Liliaceae and assigned to the family Xanthorrhoeaceae, subfamily Hemerocallidoideae. Xanthorrhoeaceae was renamed in 2016 to Asphodelaceae in the APG IV system. Learn more at Wikipedia.
Eastern bluebirds! Males are a royal blue on the back and head, and a red-brown on the breast. Skokie Country Club, Don Cross, Jul 10, 2023. For more about bluebirds see The Cornell Lab’s All About Birds.

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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.