May! Poa Seedheads, Bipolaris Leaf Spot, Cyst Nematodes, and Bentgrass Variety Research
It was a stormy end to April. It was not just a reminder of how turbulent weather can create a mess. It was real. The Midwest was clobbered with severe thunderstorms and tornadic activity. And if you were viewing it in real time, on social media, you saw more than a few twisters. It was scary. Next, it should be obvious happens if you are a highly maintained golf course or landscape — a lot of labor. For golf course maintenance teams, addressing tree debris (insert weak branching species here) and sand bunker washouts (insert designs with steep faces here) is just part of what has to be done. But planning for those additional costs are near impossible. Today, a greater investment and emphasis on the planning and maintenance of trees, as well as newer methods to construct bunkers are making a difference (less devistation by wind and rain). In 2024, we are creating a new education video series which will address both construction of sand bunkers, as well as selection and maintenance of desirable trees.
On golf courses this week, creeping bentgrass started to grow with vigor (for the first time this spring). We can tell. Any aerification holes of surfaces saw a quick heal and new, white roots quickly filled to enjoy their new unobstructed path down. And on home lawns this week, Kentucky bluegrass leaf blades saw their first cut (insert the growl of lawnmowers here). And our trees? The oaks are now leafing out without hesitation. And our dogwoods, Cornus florida, in Chicago’s North Shore were in full bloom/full glory. And did you ask about our diagnostic samples and turfgrass research? Well those started to take off too. Our 2024 growing season is now in another gear — this shoulder season is no longer hitting the breaks. Mother Nature is now pressing the other pedal. How fast will we go?
Weather
Scouting for Seedheads? Annual Bluegrass or Poa annua
This week one species of turfgrass — which behaves both as a perennial (survives winter) and as an annual (produces a ton of seed) — became much more obvious if you were out on golf courses this week. Known as Poa annua or just plain Poa by those in the golf course maintenance business (and green committee members). Yes, Poa finally reached peak seedhead production in the upper Midwest. Love it or hate it, Poa represents a cosmopolitan turfgrass species that is well adapted to compete with creeping bentgrass (especially in cool, humid environments = Chicago).
Spring Timings Traditionally Used for Poa Seedhead Suppression
There are effective and well-researched strategies to suppress Poa seedhead production. For example two products, Proxy and Primo, are often combined and broadcast applied from tee to green. These PGR (plant growth regulators) applications occur in the early spring. Temperature based GDD (growing degree day) models help dial in the timing. For Chicago, those applications are typically timed late March to early April. For more information see Michigan State’s GDDTracker.
New Timings for Poa Seedhead Suppression
Newer timings are now recommended. Most golf courses are now switching to a fall timing for Poa seedhead suppression because better efficacy can result. Also, this strategy is simpler because as it only requires Proxy. For more information on this, take a look at Envu’s Fact Sheet: Fall Proxy® Applications For Improved Seedhead Control Of Annual Bluegrass.
Scouting for Disease — Bipolaris Leaf Spot of Creeping Bentgrass
Two reports of a leaf spot this week. It coincided with warming temperatures during a period that was otherwise cloudy and wet (frequent rainfall).
In one instance, it was a golf course that has a history of Bipolaris leaf spot on greens. It turns out we have learned that ‘007’ creeping bentgrass is susceptible to Bipolaris leaf spot. However, within a single creeping bentgrass variety it seems only certain biotypes are susceptible and other biotypes appear genetically resistant (previous observations). And so overall effect is always very patchy and one could argue not a very big deal. However, if wet, overcast conditions hang on for a week or longer — it can become a big deal.
Physiological Stress of Turfgrass
Leaf spots are represented by a number of fungi and all produce condia/spores during an asexual life cycle. Under ideal conditions, leaf wetness durations of 10 hours or more, turfgrasses are vunerable. However, the final kicker is stress. Most of the time healthy turfgrass has good resistance to leaf spot diseases. Known stressors are usually factors that are associated with outbreaks. Currently greens have or have been aerified and top dressed with sand. This is a significant stress. Aerification of greens can be associated with stress-related diseases such as leaf spots, anthracnose and others.
Control of Leaf Spots
Our “go to” solutions to control leaf spots still remain largely the same.
Contacts and Iprodione. On putting greens, contact fungicides such as Daconil Action (chlorothalonil) and Fore (mancozeb) are often used because they are efficacious and fungicide resistance is a concern. Another key fungicide used for leaf spot fungi is Chipco GT or iprodione.
Newer DMIs. Newer DMIs have also been found to provide broad spectrum control of things like leaf spots. They are called ‘newer’ in this case because the typical growth regulation associated with this group of fungicides has been minimized. Examples are Densicor (prothiaconazole) and Maxtima (mefentrifluconazole).
More Information. One of the best references for fungicides and their ability to control specific diseases is called Chemical Control of Turfgrass Diseases. A joint publication by The University of Wisconsin, Rutgers and
Turfgrass Cyst Nematode (Heterodera iri)
This week we began a small plot study on a putting green which will look at newer nematicide products. The site has turfgrass cyst nematodes, Heterodera iri, among others. Cyst nematodes in turf are relatively uncommon, but they are occasionally found in samples from sand-based greens in Illinois.
Historically, Randy Kane found them in creeping bentgrass/Poa annua greens at two locations during summer 2005 (personal communication). Cyst nematodes are an important genera world wide. In the United States, soybean cyst nematodes are problematic and were a focus of my former major professor Tim Todd (Kansas State University Nematology Lab) in Manhattan, KS.
Endoparasitic Nematodes in Putting Greens
Cyst nematodes are similar to root knot nematodes (Meloidogyne) given both are endoparasites of roots and both cause somewhat similar galling symptoms of roots.
Damage by Nematodes in Putting Greens?
In summer (late July), in conjunction with physiological stress and concentrated foot traffic, putting greens can suffer greater midday wilt stress given dense nematode populations. Otherwise, it is often difficult to see actual turf loss caused by nematode root parasitism.
New Creeping Bentgrass Varieties for Dollar Spot Resistance by Shehbaz Singh, MS
A creeping bentgrass variety trial that uses a randomized complete block design with four replications has been established at the Bob Berry Sunshine Course in Lemont. The variety trial site is a USGA specification rootzone which was previously used for two creeping bentgrass green variety trials. Originally it was a 2004-09 National Turfgrass Evaluation Program (NTEP) creeping bentgrass variety trial and the second was a 2009-2012 North Central Region (NCERA) study to evaluate newer varieties for low input use with regard to fungicides for dollar spot. NCERA is a collaboration of a majority of Midwestern turfgrass researchers.
Newly Added Varieties
Previously, the trial had a total of 18 creeping bentgrass varieties. On Apr 30, 2024 two new varieties were added ‘Spectrum’ and ‘Matchplay’ from Landmark Seed Company. This was an area which also contained the USGA specification root zone. Existing ‘RTF’ tall fescue was killed using one application of glyphosate on Apr 10, 2024. The seeding area was hand-raked to prepare for interseeding into nonliving tall fescue. The seeding rate was 1 lb per 1000 sq ft with about 15 g of bentgrass seed used per 8 ft x 4 ft plot. Seed was mixed with a slow-release fertilizer (e-Corganite 4–3–0) to aid distribution uniformity when applied. Light hand watering was done to moisten the newly seeded area. After seeding, the plot area was covered with black Economy Landscape fabric to aid bentgrass seed germination.
Information regarding ‘Spectrum’ and ‘Matchplay’ creeping bentgrass can be found on the Landmark Seed Company website.
Objectives
- Evaluate establishment rate of bentgrass cvs
- Evaluate dollar spot susceptibility of bentgrass cvs
- Evaluate other desirable characteristics such as spring green up of bentgrass cvs
Materials & Methods
- Each plot (4 ft x 8 ft) was hand-seeded on Aug 28, 2023 at a rate of 1 lb per 1000 sq ft
- Slow-release fertilizer was mixed with seed (Forever Green natural, 4–3–0)
- Grow in saw minimal inputs; 0.15 lbs N per 1000 sq ft as liquid urea on Oct 4, Oct 10 and Oct 19 in 2023
- Slow-release granular fertilizer, Forever Green natural 4–3–0, at 0.5 lbs N per 1000 sq ft applied on April 16, 2024
Data Collection– Every two weeks
- Visual Quality (1–9 scale, with 6 = minimum acceptable and 9 = best)
- Normalized Difference Vegetation Index (NDVI) using GreenSeeker/Trimble HCS-100
- Visual Turf Cover (% per plot)
- Visual Dollar Spot (% and number of spots per plot)
- Discoloration of Dormant Turf (% per plot) during winter months
- Spring Greenup (1–9 scale, with 6 = minimum acceptable and 9 = best)
Visual Spring Greenup
No statistical differences were observed among 18 creeping bentgrass varieties for visual spring green-up ratings. However, a few entries such as Centennial, PST-OMRN, and PST-OR2O were the first to show acceptable green-up in spring 2024. The standards of Mackenzie and Pure Distinction had 4.75 and 4.5 visual spring green-up respectively on May 1, 2024.
Normalized Difference Vegetation Index (NDVI)
A significant difference among creeping bentgrass was observed for NDVI on May 1, 2024. NDVI for PST-OR2O was significantly higher than Flagstick. NDVI data followed similar trends as visual spring green-up ratings. PST-OR2O showed a spring green-up of 6.25 whereas Flagstick saw a visual spring green-up rating of 4.25.
Final Photo
