Drying (trying)! Saturated Soils, Summer Patch, Fairy Ring, and Dollar Spot Research

CDGATurfgrassProgram
6 min readJul 26, 2024

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The forecast had promised we would dry. And we did. It was a pleasure to experience a drop in humidity for a day or two. A lessening of water puddles happened in the lowest areas of every creeping bentgrass fairway. However, as quickly as it came, it left — humid air with cloud cover returned. In a week, severe thunderstorms would lash Chicago’s north suburbs and one course recorded ~6 inches of precipitation in 8 days. Without a doubt golf course fairways have been hardest hit in 2024. Our native soils are both strong (among the most fertile), and weak (drainage can be problematic). “Illinois is known for its “black dirt” with Drummer silty clay loam being the most common. The Drummer soil series consists of very deep, poorly drained soils that formed in 40 to 60 inches of loess or other silty material and in the underlying stratified, loamy glacial outwash; under native prairie vegetation.” USDA Natural Resources Conservation Service

Image 1. After a brief break from both humidity and cloud cover, rain returned to Chicago. Growing season 2024 continues to see a pattern of frequent rainfall, Arrowhead Golf Club, Wheaton, IL. Settle, Jul 25, 2024

In the landscape, a major disease of lawns has begun. Known as summer patch, it is the most common fungal root rot of bluegrass (Poa). The best two solutions are non-chemical: 1) Utilize higher heights of cut (low mowing heights increase plant stress) and, 2) conduct annual aerification events (compacted soils choke normal root growth). Believe it or not, aerification is already a hot topic for some Chicagoland golf courses given newer summer timings for aerification (mid-August) being implemented. Late summer aerification captures rapid creeping bentgrass growth and is also a good strategy to kick-start root recovery early. If you look it up, “Better through Golf” is the mission of the Chicago District Golf Association. “Better through Roots” is without a doubt the unofficial mission of every golf course superintendent.

Weather

Figure 1. Temperatures have remained cool for an extended period in northern Illinois, Bob Berry Sunshine Course, Lemont, IL.
Figure 2. Mean temperature anomaly from July 30 through August 5. The next 7 days will see a transfer of heat from the west coast to the Midwest. Illinois will see air temperatures 4 to 6 degrees above normal (red colors). Meanwhile, states along the Gulf Coast and the southeastern U.S. will stay cooler than normal. courtesy WGN Weather Blog

Scouting for Disease — Summer Patch (Magnaporthiopsis poae)

Summer patch is a root, crown and stem disease of annual bluegrass, Kentucky bluegrass and fine fescue. It develops under periods of plant stress during periods of hot weather. Our first outbreaks of summer patch weren’t unexpected. They occurred in a week that followed a rapid dry down. Roots were already infected. Frequent rainfall had likely masked the development of symptoms.

Image 1. Summer patch symptoms (yellow rings) on the edge of a green where meets the fairway approach. This can be a difficult disease to diagnose because there are many look-a-likes.
Image 2. Closeup of a single small summer patch (2 inches in diameter) in a creeping bentgrass/Poa annua green surface. Note: Only the Poa portion (yellow leaves) is negatively impacted. Settle, Jul 25, 2024
Image 3. Microphotograph (400x) of a rotted Poa annua root. Runner hyphae (lower left) and fungal resting structures (upper) can be seen. Settle, Jul 25, 2024

Solutions for Summer Patch

Cultural Practices are Key

  1. Relieve compaction with core aerification in the spring and fall
  2. Maintain soil pH between 5.5–6.0
  3. Ammonium-based fertilizers appear to reduce symptoms, while nitrate forms increase severity. Urea forms seem to have a neutral affect.

Excellent Penn State Fact Sheet

Turfgrass Diseases: Summer patch (Causal fungus: Magnaporthiopsis poae) by Peter Landschoot, PhD

Fungicides

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

Click Here

Scouting for Disease — Fairy Ring (multiple basidiomycete fungi)

Wet followed by dry conditions are often associated with fairy ring. Fairy ring can be especially damaging in golf putting greens. Dr. Mike Fidanza has spent a majority of his career working on this particular turfgrass “disease”. In the article Fairy Ring 101, he describes in detail what happens in turfgrass systems. Here are some bullet points:

  • Fairy ring indirectly causes turf damage by disrupting the environment below the surface.
  • Type-I fairy ring symptoms are the most severe and are associated with necrotic or dead turf.
  • Development of hydrophobicity or soil water repellency in the rootzone is one factor.
  • Another factor is the accumulation of ammonium to levels toxic to plant roots.
Image 1. Type 1 fairy ring is among the most difficult problems that golf course superintendents ever face in their career when managing sand-based root zones like golf putting greens. Preventative fungicide programs in the spring are preferred because curative control in the summer is often difficult to achieve. Settle, Jul 24, 2024
Image 2. A ten treatment study with 4 replications is looking for ways to improve curative control of type 1 fairy ring on a golf putting green. A new experimental by BASF is being investigated. All fungicides are applied with and without a wetting agent (Excalibur by Aqua Aid Solutions). Settle, Jul 24, 2024

Solutions for Fairy Ring

Control of fairy ring relies heavily on cultural practices like wetting agents. Newer DMI fungicides are also of interest because they can offer broad suppression of fairy ring fungi with minimal turfgrass growth regulation. See newest 2024 recommendations in PPA-1: Chemical Control of Turfgrass Diseases 2024 (uky.edu).

Click here

Evaluate spoon-feeding fertility to improve plant health and its ability to reduce fungicide inputs in a creeping bentgrass green by Shehbaz Singh, MS

An Aquatrols fertility trial is being conducted to evaluate its influence on dollar spot disease development in a creeping bentgrass nursery green. The objective was to determine if fertility products can maintain acceptable dollar spot control with reduced fungicide inputs. The study is being conducted at North Shore Country Club in Glenview, IL.

Image 1. An Aquatrols fertility study is being conducted in a ‘‘SR1119’ plus ‘Providence’ creeping bentgrass nursery green (with 10–20% Poa annua) at North Shore Country Club in Glenview, IL. Settle, Jul 8, 2024

Material and Methods

The small plot study has 10 treatments in a randomized complete block design with 4 replications. Each individual plot size is 4 ft by 6 ft. Data shown reflects two (28 day) or three (14 day) applications on June 11, June 24, and July 8.

Table 1. Treatments for a Aquatrols fertility + fungicide study conducted in a ‘SR119’ plus ‘Providence’ creeping bentgrass nursery green. North Shore Country Club, Glenview, IL.

Objectives

  • Determine if fertility products can maintain acceptable dollar spot control with reduced fungicide inputs
  • 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)
  • Silvery Thread Moss (% per plot)
  • Color/Phytotoxicity (1–9 scale)

Dollar Spot Disease

Dollar spot disease incidence was minimal during June given cool temperatures were experienced. During July rapid development of dollar spot occurred. For example, on July 1, dollar spot in untreated plots was ~10%, but reached 35% two weeks later on July 15.

Daconil Action at 14-day Interval

Dollar spot in treatments of fertility products + Daconil Action 4 oz (full rate) remained acceptable (less than 10%). Under increased dollar spot disease pressure (Jul 8-22), the half rate of Daconil Ultrex was no longer able to maintain acceptable disease control regardless of additional fertility (Fig. 1).

Visual quality agreed with disease ratings and the half rate of Daconil Ultrex was unable to maintain acceptable visual quality regardless of additional fertility (Fig. 2).

Figure 1. Dollar Spot given spoon-feeding fertility plus Daconil Action (2 or 4 fl oz) applied at 14-day intervals in a creeping bentgrass nursery green. The 14-day applications were Jun 11, Jun 24 and Jul 8. North Shore Country Club, Glenview, IL
Figure 2. Visual Quality given spoon-feeding fertility plus Daconil Action (2 or 4 fl oz) applied at 14-day intervals in a creeping bentgrass nursery green. The 14-day applications were Jun 11, Jun 24 and Jul 8. North Shore Country Club, Glenview, IL
Image 2. Photos given spoon-feeding fertility plus Daconil Action (4 fl oz) applied at 14-day intervals in a creeping bentgrass nursery green. The 14-day applications were Jun 11, Jun 24 and Jul 8. North Shore Country Club, Glenview, IL. Singh, Jul 22, 2024
Image 3. Photos given spoon-feeding fertility plus Daconil Action (2 fl oz) applied at 14-day intervals in a creeping bentgrass nursery green. The 14-day applications were Jun 11, Jun 24 and Jul 8. North Shore Country Club, Glenview, IL. Singh, Jul 22, 2024

Daconil Action at 28-day Interval

The full rate of Daconil Ultrex was unable to maintain acceptable disease control regardless of additional fertility beyond 14 days (Fig. 3).

However, of all treatments, CarbN + Fusion was different and the only treatment able to provide acceptable visual quality on 1 Jul and 8 Jul when dollar spot disease pressure was moderate (Fig. 4).

Figure 3. Dollar Spot given spoon-feeding fertility plus Daconil Action (4 fl oz) applied at 28-day intervals in a creeping bentgrass nursery green. The 28-day applications were Jun 11 and Jul 8, 2024. North Shore Country Club, Glenview, IL
Figure 4. Visual Quality given spoon-feeding fertility plus Daconil Action (4 fl oz) applied at 28-day intervals in a creeping bentgrass nursery green. The 28-day applications were Jun 11 and Jul 8, 2024. North Shore Country Club, Glenview, IL
Image 4. Photos given spoon-feeding fertility plus Daconil Action (4 fl oz) applied at 28-day intervals in a creeping bentgrass nursery green. The 28-day applications were Jun 11 and Jul 8. North Shore Country Club, Glenview, IL. Singh, Jul 22, 2024

Final Image

This is ‘Limelight’. Hydrangeas are well adapted for the upper Midwest like Evanston, Illinois. Settle, Jul 26, 2024

Hydrangea paniculata, or panicled hydrangea, is a species of flowering plant in the family Hydrangeaceae native to southern and eastern China, Korea, Japan and Russia (Sakhalin). It is a deciduous shrub or small tree, 3.3-16.4 ft tall by 8 ft broad, growing in sparse forests or thickets in valleys or on mountain slopes. In late summer it bears large conical panicles of creamy white fertile flowers, together with pinkish-white sterile florets. Florets may open pale green, grading to white with age, thus creating a pleasing “two-tone” effect.” For more see Hydrangea paniculata — Wikipedia.

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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.