Dry Conditions: Fairy Ring, Anthracnose, Summer Patch and Divot Research

6 min readAug 19, 2022

And just like that. Temperatures at night have cooled and it feels like fall. However, in the landscape Chicago’s cool-season lawns are beginning to look more and more dilapidated and dry. It was the second week in a row without any appreciable rainfall for a majority of us. The last time things looked this bone dry was sometime in June. Nevertheless, we are now on the other side of summer and temperatures will keep going down. Plants are much more tolerant of drought when heat stress is out of the picture. But we still need to practice a level of watering to address visible wilt stress. Hmm, reminds me of what I did this morning; hand-watered a fine fescue lawn and the associated drooping ‘Annabelle’ hydrangea next to the front door.

Image 1. During dry conditions, type 2 fairy ring appears on a ‘Pure Select’ creeping bentgrass fairway, Bob Berry Sunshine Course, Lemont, IL. Settle, Aug 18, 2022

Given cooler nighttime temperatures are back in play, we are seeing change at golf courses. Kentucky bluegrass is beginning to see optimal growth again. This week, it may have looked as if we were “baling hay” as roughs were being mowed— something we last saw in May. From a trouble-shooting perspective there is also change. New problematic issues have now arrived. Things like anthracnose in golf greens; often triggered by midday wilt stress. Things like fairy ring (green rings) are more easily visible as soils dry. And a resurgence of summer patch in bluegrass; if your roots are missing due to a fungal root rot, symptoms can get worse when dry. It’s all just to say that the transition from one season to another can be challenging. Most importantly, keep enjoying summer in the great outdoors. It’s a cool time of the year. Pun intended.

Weather Update (August’s Third Week) by Shehbaz Singh, MS

North Shore CC, Glenview: The weather was mild during the most days of the evaluated period. Temperatures ranged from 56.7 to 85.4°F over last seven days. Interestingly, the week’s Tmax of 85.4°F and Tmin of 56.7°F was recorded on the same day (August 18). Overall, high temperatures slowly rose as the week progressed. The relative humidity followed a similar pattern, lower than 80% over the weekend, and higher than 80% on most days of week. Only trace rainfall was recorded for northern suburbs. The cumulative rainfall was 0.07 inches.

Figures 1 and 2. Weather conditions during the third week of August. Bob Berry Sunshine Course, Lemont, IL.

Bob Berry Sunshine Course, Lemont: The air temperature ranged from 52.0 to 84.2°F over the last seven days. Temperatures in southern Chicago suburbs (Lemont) were little higher than the northern Chicago suburbs (Glenview) on most days. Air temperatures above 80°F were recorded on three days in Lemont while only one day in Glenview. The relative humidity in the southern suburbs ranged from 72 to 87% with most days having humidity lower than 80% except on August 14 when a relative humidity of 87.2% was recorded. Similar to northern Chicago suburbs no heavy rainfall occurred. The cumulative rainfall for Lemont was 0.03 inches.

Anthracnose, Collectotrichum cereale of Poa annua

One of the more aggravating diseases of golf greens showed up this week. First began approximately a week ago at a couple superintendents. This would match up when drier conditions began in the upper Midwest. Historically, anthracnose of Poa annua in sand-based golf greens was most often triggered by midday wilt stress of golf greens (personal communication: Dr. Randy Kane, Chicago District Golf Association, 1985–2005). Today, anthracnose is much better understood thanks to a great deal of research that has been conducted.

For more on how mowing and rolling and many more things can influence anthracnose please read on. Anthracnose on annual bluegrass turf: Best management practices. Murphy, Clarke and Inguagiato, 2018.

Cultural Practices or Factors that Influence Anthracnose

  • Irrigation = avoid midday wilt stress when dry
  • Fertility = complete N-P-K
  • Mowing height = higher better
  • Mowing frequency = consider rolling
  • Soil compaction = adds stress
  • Traffic or wear = reduce if possible
  • Avoid stressful events = verticutting, aeration, sand topdressing
  • Fungicide selection = fungicide resistance by C. graminicola is reported
Image 1. Anthracnose impacting a patch areas of a Poa/bentgrass golf green. Settle, Aug 18, 2022
Image 2. Closeup of thinning caused by anthracnose. Note creeping bentgrass is unaffected within the patch. Settle, Aug 18, 2022
Image 3. Dark hair-like setae fungal structures are useful for identification of anthracnose. Settle, Aug 18, 2022
Image 4. One celled, crescent-shaped conidia are useful for identification of anthracnose. Settle, Aug 18, 2022

Summer patch of Bluegrasses, Magnaporthe poae

Summer patch is still seen impacting areas of turfgrass. It has recently gotten worse. In part this is because our weather has gotten dry. Now that conditions are dry, turfgrass with rotted roots can quickly wilt and die unless supplemental water is provided. Symptoms are most often yellow rings that progress to dead rings. Eventually, the turfgrass will recolonized the center of dead patches. This is sometimes referred to as the “frog-eye” symptom.

Image 1. Summer patch negatively impacting a swale area of a Kentucky bluegrass fairway. Settle Aug 18, 2022
Image 2. Summer patch often exhibits a frog-eye symptom that is useful for identification. Settle Aug 18, 2022
Image 3. Examining Kentucky bluegrass roots. One healthy root with root-hairs is surrounded by dark roots that are no longer functional. Root rot is caused by Magnaporthe poae or summer patch. Settle, Aug 18, 2022

Creeping Bentgrass Divot Study Update by Shehbaz Singh, MS

Spring Divots. For the spring trial, the divots were made on April 19 and filled very next day with divot mix treatments. Data is collected on weekly basis from the day of divot making. Finally, after 16 weeks (3.5 months) of evaluation a majority of divot mixes were found able to provide at least 90% of recovery.

Best and Worst. Trends show the 8–1–1 divot mix with seed (bentgrass + chewings fescue) was among the first treatments to fully recover. It matched recovery by replacing a sod piece. Divot mixes with seed added showed earlier recovery compared to mixes without seeds.

The divot mix with sand only was similar to untreated or an unrepaired divot. Both showed very slow recovery in comparison to all other divot mixes. More results and conclusions can be drawn once data from all parameters is analyzed statistically (visual quality, Normalized Difference Vegetation Index, soil moisture and soil temperature).

  • Best Performers in Spring - Divot mixes with seed were quick to recover
  • Worst Performers in Spring - Sand only divot mix and untreated
Figure 1. Visual estimate of creeping bentgrass recovery (%) for 11 different divot mixes (spring divot study).

Summer Divots. For the summer trial, the same experimental set up and divot mixes were used. Divots were made on June 23 and filled with respective treatments on the very same day. This trial is now at week 7 and some treatments are already showing full recovery. Compared to the spring trial, the recovery in the summer trial is quicker. This is probably due to the vigorous growing nature of creeping bentgrass in the summer season. Interestingly, one divot mix that performed well in the spring trial is not performing well in the summer trial (e.g., 8–1–1 divot mix plus seed (bentgrass + chewings fescue)).

  • Best Performers in Summer - Compost mix plus seed(bentgrass + chewings fescue) divot mix and repairing with a sod piece
  • Worst Performers in Summer - Divot mixes without seed (similar to spring season)
Figure 2. Visual estimate of creeping bentgrass recovery (%) for 11 different divot mixes (summer divot study).

Final Photo

A bumble bee found hard at work pollinating garden phlox (P. paniculata) in Evanston, IL. Settle, Aug 15, 2022




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