August Heat! Anthracnose, More ABW, Fairy Ring, and Dollar Spot Research

CDGATurfgrassProgram
8 min readAug 2, 2024

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The summer we had been expecting (some had forecasted) finally arrived. The hot one. It’s August and so not entirely unexpected. Up to now, conditions have been very unlike summer — unseasonably cool periods would interrupt July’s heat. However, there has been one constant. The rain. “July was a remarkably wet month in Illinois, likely a top 5 wettest July on record. The unofficial July rainfall for St. Clair County is just over 13 inches, which would be a full 5 inches higher than the **previous record**.” Illinois State Climatologist, X social media post, Aug 1, 2024. (Note: St. Clair County is located directly east of St. Louis, MO)

Image 1. It was a record wet July and a ‘Providence’ plus ‘SR1119' creeping bentgrass nursery green delivered record amounts of silvery thread moss (left corner = untreated) which is good for researchers, but not-so-much for superintendents. North Shore Country Club, Glenview, IL. Settle, Jul 29, 2024

In the landscape, record breaking precipitation has meant way more growth than usual. Just look up as certain native flowers are quite tall. Some can attain maximum heights of 6-8 ft or more. An overly wet summer has also meant grassy weeds (crabgrass) is a greater part of the turfgrass mix in lawns. On golf courses, a preventative approach to plant health reached maximum benefit as July transitioned to August. Up to now, those inputs have protected and allowed for more root growth which provides ‘more fuel in the tank’. A stressful period of physiological decline often happens to creeping bentgrass greens about midsummer. It’s just a fact of life when, among other things, you are clipped daily at a height of around 0.125 inch. In 2024, it turned out it wasn’t extended periods of heat that provided the stress. Rather, it was too much rain and low light levels (most days were with cloud cover). Do get ready because the upcoming forecast is as good as it gets — 70s for highs and we are to DRY!

Weather

Figure 1. High temperatures did not exceed 90 degrees for a majority of days in July, Bob Berry Sunshine Course, Lemont, IL.
Image 2. Precipitation forecast. During August’s first week, drier conditions are predicted in the Midwest (white to green colors). Map courtesy NOAA

Scouting for Disease — Anthracnose (Colletotrichum cereale)

Anthracnose is one disease that we do not like at all. Probably the most feared fungal disease of Poa annua greens and rightly so. However, through the years we’ve gotten better when it comes to understanding how to deal with anthracnose. And it is a good lesson in how cultural practices (non-chemical methods) are probably the most important component when it comes to avoiding anthracnose.

To be fair, newer fungicides have also played a part in lessening the golf course superintendent fear of anthracnose. Great options now exist. Many of the newer broad spectrum DMIs control anthracnose. Also some newer SDHIs offer control of anthracnose (check the label). In contrast, QoIs are effective, but are prone to the development of fungicide resistance by anthracnose.

Additionally, new greens now enjoy the best genetics to date. True dwarf creeping bentgrasses with superior qualities are not threatened much at all by anthracnose — assumes creeping bentgrass is maintained with practices that encourage good plant health.

Image 1. Anthracnose symptoms (yellow-orange patch) on a sand based green. A difficult disease to diagnose in the field because easily confused with localized dry spot or a common root rot of bentgrass known as take-all patch. Settle Jul 29, 2024
Image 2. A dissecting microscope is used to initially examine the sample. Affected plants are found to be Poa annua only, whereas the creeping bentgrass component remains green and perfectly healthy. Settle, Jul 29, 2024
Image 3. A dissecting microscope is used to find a fungal structure called setae and used for anthracnose identification. Settle, Jul 29, 2024
Image 4. A compound microscope is used to provide a close up of fungal structures associated with anthracnose (hair-like setae). Settle, Jul 29, 2024

Simple Cultural Practice Solutions for Anthracnose

  1. Provide proper fertility (nitrogen)
  2. Increase mowing height
  3. Topdress with sand
  4. Avoid drought stress

Excellent article on anthracnose from Rutgers Univ

Full 2018 article in GCSAA’s Golf Course Management (click below)

Anthracnose on annual bluegrass turf: Best managements practices by James Murphy, PhD; Bruce Clarke, PhD; and John Inguagiato, PhD

“The severity of anthracnose is strongly linked to deficiencies in nitrogen and potassium that affect the health of annual bluegrass.”

Fungicides

See newest 2024 recommendations in PPA-1: Chemical Control of Turfgrass Diseases 2024 (uky.edu).

Click Here

Scouting for a New Pest — Annual Bluegrass Weevil (Listronotus maculicollis)

Two more occurrences of annual bluegrass weevil (ABW) were reported and verified in the final week of July. The total number of golf courses in Chicago with confirmed ABW is now up to 9. We continue to monitor for a new pest called annual bluegrass weevil or simply ABW.

The significance of this pest is that traditional insecticides which have been used for annual white grub control (Acelepryn) does not provide adequate control for ABW larvae. Also, the required timing for ABW is earlier.

Annual Bluegrass Weevil Fact Sheet

Dr. Ben McGraw has a current fact sheet that has everything you need to know. Newer insecticides offer good control of annual bluegrass weevil.

Click here

Scouting for Disease — Fairy Ring (multiple basidiomycete fungi)

Type 1 fairy ring (1 = brown, dead rings) can be a chronic problem. Sand based putting greens just another place where the fungi can establish to degrade an organic matter food source (mainly turfgrass thatch). The fungi are not directly parasitic.

And so here we go again. An outbreak on the same green in midsummer. The same areas that saw negative effects in 2023 see negative effects in 2024. Historically the same property saw significant type 1 fairy ring injury on greens and fairways during a record hot summer in 2012. We know this particular fairy ring likes it hot!

Image 1. Type 1 fairy ring impacting a Poa annua/creeping bentgrass green surface. It is very difficult to diagnose because no fruiting structures are occurring (mushrooms or puff balls). This fairy ring is associated with peak summer heat each year on a property that has a history of an aggressive fairy ring outbreak (2012). Settle, Jul 30, 2024
Image 2. Type 1 fairy ring damaged turf then becomes vulnerable to blue-green algae (cyanobacteria) development. Algae quickly colonizes any open voids on thin putting green surfaces. Settle, Jul 30, 2024

Fungicides for Fairy Ring

See newest 2024 recommendations in PPA-1: Chemical Control of Turfgrass Diseases 2024 (uky.edu).

Click here

Evaluate the additional benefits of surfactants to suppress dollar spot disease in creeping bentgrass by Shehbaz Singh, MS

A Rhizosolutions study is being conducted to evaluate the efficacy of surfactants to suppress dollar spot disease. The objective was to determine if certain surfactants can reduce dollar disease development and thus help to reduce fungicide inputs. The study is being conducted on practice range tee in play at North Shore Country Club in Glenview, IL.

Image 1. A RhizoSolutions study to evaluate dollar spot disease development given reduced inputs is being conducted on a creeping bentgrass practice range tee at North Shore Country Club in Glenview, IL. Settle, Jul 29, 2024

Material and Methods

The small plot study has 7 treatments in a randomized complete block design with 4 replications. Individual plot size is 4 ft by 6 ft. Applications were every 14 days with the first application made on May 20, 2024.

Table 1. Treatments for a Rhizosolutions study conducted in a creeping bentgrass practice range tee, North Shore Country Club, Glenview, IL.

Objectives

  • Determine if surfactants can provide acceptable dollar spot control given reduced fungicide inputs (acceptable threshold = 10% or less)
  • Evaluate dollar spot control of surfactants
  • Evaluate turf quality
  • Evaluate any phytotoxicity

Measurements

  • Visual Quality (1–9 scale, with 6 = minimum acceptable and 9 = best)
  • Normalized Difference Vegetation Index (NDVI) using GreenSeeker/Trimble HCS-100
  • Dollar Spot (% per plot)
  • Dollar Spot Count (infection center number per plot)
  • Color/Phytotoxicity (1–9 scale)

Results — Dollar Spot Disease

Very high dollar spot disease pressure occurred in 2024 due to frequent rainfall and few days with peak heat (90+ degrees). As expected, untreated saw highest disease levels and dollar spot was observed to exceeded 20% by late July. Nevertheless, a majority of treatments effectively suppressed dollar spot below the 10% threshold until early July. After July 8, disease pressure increased significantly.

Trend of Best Dollar Spot Control. Dewcure 4.0 oz and Daconil Ultrex 1.8 oz maintained best-sustained control with less than 5% dollar spot by the end of July. The combination treatment (Daconil Ultrex 1.8 oz + Rhizo 3887 2.0 oz) and the alternate treatment (Rhizo 3887 2.0 oz and Daconil Ultrex 1.8 oz) also showed good control, staying below 5% until mid July and below 10% by the end of July.

Moderate Dollar spot Control. Rhizo 1002 3.0 oz alone and Rhizo 3887 2.0 oz alone provided moderate control with dollar spot exceeding 10% from mid July on.

In summary, all treatments showed dollar spot suppression early on, but their effectiveness diminished as disease pressure increased. The combination and rotation strategies showed good performance for extended control.

Figure 1. Percent Dollar Spot in a creeping bentgrass practice range tee. Applications were every 14 days with the first application made on May 20, 2024. North Shore Country Club, Glenview, IL

Visual Turf Quality

Turfgrass visual quality ratings were a direct reflection of dollar spot control. No phytotoxicity was ever observed.

Trend of Best Visual Quality Required Fungicide. Daconil Ultrex 1.8 oz consistently outperformed other treatments, maintaining visual quality above 6.0 for most of the study period. The combination of Daconil Ultrex 1.8 oz + R3887 2.0 oz and the alternating treatment of Rhizo 3887 2.0 oz followed by Daconil Ultrex 1.8 oz also showed strong results, generally staying above the acceptable level after mid-June.

Visual Quality Improved With Time. Dewcure 4.0 oz improved over time, reaching and maintaining acceptable quality from early July. Previous CDGA research (2010) also showed Dewcure can suppress dollar spot, but a risk of phytotoxicity was found to exist in an L-93 creeping bentgrass fairway situation. However, Dewcure phytotoxicity did not occur in the current tee study.

Inconsistent Visual Quality. Surfactants alone (Rhizo 1002 3.0 oz, Rhizo 3887 2.0 oz). Those two treatments were most often below the acceptable threshold.

Worst Visual Quality. The untreated control mostly remained below 6.0. In July, dollar spot disease development steadily reduced visual quality of untreated.

Figure 2. Visual Turf Quality (1–9 scale) in a creeping bentgrass practice range tee. Applications were every 14 days with the first application made on May 20, 2024. North Shore Country Club, Glenview, IL
Figure 3. Normalized Difference Vegetation Index in a creeping bentgrass practice range tee. Applications were every 14 days with the first application made on May 20, 2024. North Shore Country Club, Glenview, IL
Image 2. Daconil Ultrex 1.8 oz consistently outperformed all other treatments in a creeping bentgrass tee. The combination of Daconil Ultrex 1.8 oz + R3887 2.0 oz and the alternating treatment of Rhizo 3887 2.0 oz followed by Daconil Ultrex 1.8 oz also showed strong results. Surfactants alone were unable to provide acceptable dollar spot control (10% or less). North Shore Country Club, Glenview, IL. Singh, Jul29, 2024

Final Image

Bee! A honey bee forages on a coreopsis flower on Bob Berry Sunshine Course in Lemont, IL. Settle, Jul 30, 2024

Coreopsis lanceolata Faunal Associations:The nectar and pollen of the flowerheads attract many kinds of insects because of their abundance and accessibility. These floral visitors include digger bees (Melissodes spp.), cuckoo bees (Epeolus spp., Nomada spp.), leaf-cutting bees (Megachile spp.), Halictid bees (including green metallic bees), dagger bees (Calliopsis spp., Heterosarus spp.), Sphecid wasps and other wasps, Syrphid flies (Eristalis spp. and others), bee flies (Exoprosopa spp. and others), thick-headed flies (Conopidae), Tachinid flies, bottle flies (Lucilia spp.), Muscid flies, butterflies, skippers, moths, and beetles (Robertson, 1929).” For more see Coreopsis lanceolata — Illinois Wildflowers Info.

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CDGATurfgrassProgram
CDGATurfgrassProgram

Written by CDGATurfgrassProgram

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

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