Soils Pass Mid 50s! Few Issues, Waitea Patch, and Dollar Spot Research
The third full week of April brought near ideal conditions for turfgrass growth on several days. The take home message here? Nothing better than cloud free days during spring in the upper Midwest. In a week, high temperatures crossed 80 degrees for the first time. Then there is less noticeable, but impactful, change. Soils have warmed past 55 degrees and continue to slowly gain heat. Few issues of greens were reported. The first maladies in March and April are behind us (snow molds, yellow patch). Kentucky bluegrass roughs and lawns are now green and growing — known for its dark green color, medium texture, and distinct boat shape leaf blade tip. Yes, Bob Berry Sunshine Course saw its first official mow of the rough.
And spring progresses. A foliar disease which causes bright yellow rings called Waitea patch appeared on Poa greens for the first time. In the landscape, about half the deciduous trees now have leaves. And the native oaks? Well they are just beginning to think about it — leafing out. Many more woody ornamentals were noticeable. If you looked up, redbud trees were suddenly in full bloom. The fragrant smell of Korean spice viburnum flowers was in the air. Actually, this spring has turned out to be more gradual than we first thought. And that’s okay. That’s normal. Next week is to see highs in the 60s with lows in the 40s. And if a gardener? Yes, there’s a frost advisory this weekend. So continue to enjoy a more “typical spring” outdoors. Just remember your jacket(s) and cover any sensitive vegetation.
Weather
Scouting for Broadleaf Weeds — Lesser Celandine, (Ficaria verna)
After speaking with a superintendent about broadleaf weeds we were seeing he mentioned one that is increasingly problematic in the Chicago forest preserves. It is called lesser celandine. Also known as fig buttercup. Anything that has a bright yellow bloom is noticeable. This one does and it will remind you of dandelion somewhat when you fist see it. However, it shares no other similarities. By June, lesser celandine simply disappears (a spring ephemeral perennial plant). It’s life strategy uses photosynthesis via early spring growth to then store carbohydrates into bellow ground tubers. Those belowground plant parts make it especially difficult to control unless a systemic herbicide is used. Removal by hand simply doesn’t work.
Lesser celandine is an invasive weed
- Basal rosette of dark green, shiny leaves
- Leaves are kidney or heart-shaped
- Aggressive creeping/spreading growth habit
- Well adapted to shade environments
- Competitive advantage = early spring growth
- Flowers elevated on single stalk with 8-12 yellow petals
- Reproduces primarily vegetatively via prolific tubers and bulblets
Invasive Species Information
See Midwest Invasive Species Information Network or MISIN
University of Illinois Fact Sheet
Lesser Celandine Becoming a Major Problem in Parts of the State
Image 1. Dandelion is a common weed in turfgrass areas and easily competes with Kentucky bluegrass as it begins to green up in the spring, Bob Berry Sunshine Course, Lemont, IL. Settle, Apr 10, 2024
Scouting for Disease — Brown Ring Patch aka ‘Waitea Patch’ (Waitea circinata var. circinata
A ‘first report’ of Waitea patch occured this week. It is most problematic on Poa annua greens during spring in Chicago. This is a Rhizoctonia disease that was given the different name of Waitea by taxonomists. Historically, the CDGA Turfgrass Program has conducted an extensive amount research on Waitea patch.
Waitea Patch Quick Facts
- On Poa greens (common), Waitea patch causes bright yellow rings which measure a few inches to 1 feet or more in diameter
- Rings can merge together to develop a “honeycomb” or “scalloped” look
- On creeping bentgrass greens (not as common), Waitea patch rings will appear orange-bronze
- A majority of systemic fungicides provide good control of Waitea patch both preventatively and curatively
- Thiophanate-methyl should be avoided with regard to Waitea patch; research has shown it can increase this disease
CDGA Research on Waitea — excerpt from a 2010 preventive fungicide study at Biltmore Country Club in N. Barrington, IL
“At this site in 2008, 2009 and 2010, Waitea symptoms first occurred on 22 May, 18 May, and 25 May respectively. In all years, Waitea disease developed into June, but symptoms were absent in months thereafter. During autumn, Waitea is infrequently reported on Chicago greens for unknown reasons. Untreated plots saw peak disease development on 25 May with 13% damage by Waitea, and by 9 Jun disease symptoms naturally ended. Compared to the untreated control, all treatments reduced both Waitea percent and number except Daconil Ultrex and Harmonizer-alone. The remainder of fungicides tested allowed only trace levels (2% or less) of Waitea on all dates rated…”
Preventive control of brown ring patch and Microdochium patch on a Chicago Poa annua golf green, 2010. Authors: Settle, Sibicky, Rincker
Curative control of brown ring patch on a Poa annua golf green in Chicago, 2009. Authors: Settle, Rincker
Fungicide programs on greens for disease control, 2023. by Shehbaz Singh, MS
This study was sponsored by Syngenta and was initiated as an early curative to address dollar spot of a golf green. In 2023, especially dry weather conditions in the spring delayed dollar spot development until summer. Therefore, first fungicide application was made only after dollar spot development began on July 31, 2023.
Objectives
- Evaluate two fungicide programs for dollar spot control
- Estimate turf quality visually (1–9 scale) and electronically by Normalized Difference Vegetation Index (NDVI)
Materials and Methods
The study was conducted using a randomized complete block design and used 3 treatments with 4 replications. Individual plot size was 4 ft x 6 ft.
Fungicides were sprayed using a CO2 backpack sprayer at 40 psi that used three nozzles with XR TEEJET 800VS and applied water equivalent to 2 gals per 100 sq ft. A total of 5 applications were made for each treatment (see table 1).
Data Collected
- Dollar Spot (% per plot)
- Visual Quality (1–9 scale, with 6 = minimum acceptable and 9 = best)
- Normalized Difference Vegetation Index (NDVI) (GreenSeeker/Trimble HCS-100)
- Localized dry spot (% per plot)
- Yellow tuft (% per plot)
Dollar Spot
2023 Data. Average dollar spot in experimental plots was 5.4% at the start of the study. By study end (Oct 6, 2023) dollar spot had peaked with 57.5% plot damage in untreated plots. Both programs effectively controlled dollar spot (Fig 1.).
2024 Data. By spring (Apr 15, 2024) residual dollar spot injury was still evident and plots were rated. Natural recovery had occurred during a relatively mild winter and spring. Nevertheless, untreated plots remained significantly damaged by residual dollar spot infection centers. (Fig 2.)
Visual Quality
2023 Data. At study start, visual quality of all treatments was lower than a minimum acceptable turf quality of 6.0. By study end (Oct 6, 2023), visual quality for both programs was 7.5 whereas untreated, badly damaged by dollar spot, remained unacceptable. The addition of Appear II in both programs enhanced the green color of creeping bentgrass turf (Fig 1.).
2024 Data. Nine months after the study had started residual dollar spot damage was still present and negatively impacting visual quality of untreated plots. However, the visual quality for both programs was acceptable (Program 1 was 6.5 and Program 2 was 6.0) (Fig. 2).
Normalized Difference Vegetation Index
2023 Data. At study start an average NDVI of 0.69 was recorded for all treatments. At the end of the study (Oct 6, 2023), NDVI of untreated was significantly lower than fungicide program treatments (Fig. 5).
2024 Data. Nine months after the study had started residual dollar spot damage was still present and negatively impacting NDVI of untreated plots with a reading of 0.46. The NDVI for both programs was greater concurant with greater turfgrass density. NDVI readings of both Programs 1 and 2 was 0.55 and 0.59 respectively (Fig. 6).
