August Heat! Anthracnose, More ABW, Fairy Ring, and Dollar Spot Research
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)
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
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.
Simple Cultural Practice Solutions for Anthracnose
- Provide proper fertility (nitrogen)
- Increase mowing height
- Topdress with sand
- 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).
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.
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!
Fungicides for Fairy Ring
See newest 2024 recommendations in PPA-1: Chemical Control of Turfgrass Diseases 2024 (uky.edu).
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.
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.
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.
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.
Final Image
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.
