Summer Heat Breaks: Dollar Spot, Brown Patch and Sand Bunker Research

It’s August after all, and so when our forecasted temperatures began looking more like September it was surprising to say the least. A reprieve from 90 degree highs — dog days of summer — is always welcome. Meanwhile, in the landscape it was increasingly difficult not to notice hydrangeas. One stand out species is panicle hydrangea or H. paniculata. Currently in peak bloom, there are many varieties out there of H. paniculata. And yes, I took a photo or two.

Image 1. A nice lesson of mowing height use in turfgrass management. Each one is impactful depending on your perspective (design, maintenance, aesthetics and play). Ridge Country Club, Chicago. Settle, Aug 11, 2022

Image 2. NOAA seasonal forecast (Aug-Sep) for normal rainfall in the Midwest is a flip of a coin (50/50 chance). Compare that to the Mid-Atlantic region where they may see greater than normal rainfall. More info here

This week was a break from high temperature stress issues such as physiological decline. This week was a break from concerns of the sleep-robbing superintendent disease Pythium blight (requires peak heat). All in all, it was a very comfortable week in the great outdoors. Though we did see some other action. Warm temperatures plus rain events and high humidity earlier in the week did produce dollar spot, brown patch and some X-file stuff (algae and/or slime molds can create panic on greens). From here on out we will be thinking fall more and more. On the temperature-side, no worries. We now have reached the Golden Rule of mid-August. If you are a manager of cool-season turfgrass, it means much less environmental stress. On predictions of precipitation, it indicates we may be dry in the upper Midwest. Stay tuned as that will be a developing story. Do keep enjoying summer 2022.

by Shehbaz Singh, MS

North Chicago, Glenview: The air temperature in northern Chicago suburbs ranged from 56 (lowest low) to 95 °F (highest high) over the period of last seven days. Higher air temperatures were recorded early in the week. Temperature highs ranged from 83 to 95°F and the highest air temperature was experienced on Aug 7 (Saturday). Temperature lows were generally higher than normal and ranged from 65 to 74°F. As the week progressed, air temperatures became milder. The relative humidity was quite higher during the last seven days and it ranged from 78 to 95%. The cumulative rainfall for northern Chicago suburbs was about 0.5 inch over seven days. For example, moderate rainfall of 0.25 inches fell on both Aug 7 and Aug 8 in Glenview.

Figures 1 and 2. Weather conditions during the second week of August. North Shore Country Club, Glenview, IL

South Chicago Suburbs: Similar air temperature conditions occurred in the south suburbs. Relative humidity in southern Chicago suburbs ranged from 72 to 96%. Highest relative humidity of 96% was recorded on Aug 8th. Lower humidity conditions prevailed towards the end of the week. The cumulative rainfall of 0.01 inches was recorded for southern Chicago suburbs over last seven days.

Dollar Spot, Clarireedia jacksonii

Peak disease pressure of dollar spot was first encountered approximately a month ago. Well it returned this week when it felt more like Seattle, Washington that Chicago, Illinois. Two dollar spot studies tell the story. They both use a randomized complete block design. Each study is replicated 4 times.

Image 1. Dollar Spot vs Greens: We just experienced our second jump of dollar spot disease pressure on a creeping bentgrass nursery green (L93 plus Providence). The first jump occurred between rating dates of Jul 13 to Jul 18. The second jump occurred between rating dates of Aug 1 to Aug 9. North Shore Country Club, Glenview, IL. Settle, Aug 9, 2022

Image 2. Dollar Spot vs Greens: A treatment with good efficacy versus dollar spot, North Shore Country Club, Glenview, IL. Settle, Aug 9, 2022

Image 3. Dollar Spot vs Greens: A treatment with poor efficacy versus dollar spot, North Shore Country Club, Glenview, IL. Settle, Aug 9, 2022

Figure 1. Dollar Spot vs Greens: Dollar spot progression of two dollar spot studies on a creeping bentgrass nursery green in 2022. Two big jumps in the studies coincided with optimal conditions in summer for disease development; warm nights (70s F) + extended periods of leaf wetness (10 hours or more). North Shore CC, Glenview, IL

Brown Patch, Rhizoctonia solani

Brown patch development occurred throughout Chicago this week. We observed brown patch for the first time in a study that is looking at nematode control. The study uses a randomized complete block design and is replicated 6 times. A newer experimental may also provide suppression of brown patch when applied every 14 days or every 28 days.

Image 1. Brown Patch: Identifying brown patch damage (foreground) on a creeping bentgrass practice tee. North Shore Country Club, Glenview, IL

Image 2. Brown Patch: Rating percentage of brown patch damage within a 4 ft by 4 ft treatment plot on a creeping bentgrass practice tee. North Shore Country Club, Glenview, IL

Figure 1. Incidence of brown patch in a nematicide study on a tee box. Applications were made every 14 days (Jun 13, Jun 22, Jul 13, Jul 25) or every 28 days (Jun 13 and Jul 13) at North Shore Country Club, Glenview, IL.

Sand Bunker Research by Shehbaz Singh, MS

At Bob Berry Sunshine Course in Lemont, there are three different types of bunkers. A brief information on all these bunkers are as follows:
1. Capillary Concrete. This bunker liner is constructed according to capillary concrete bunker system. Bunker liner base is developed using a specially formulated mixture of acceptably sized aggregate, various proprietary additives and water. The final product is known as ‘capillary concrete’.

• Capillary Concrete liner depth is 2 inches
• Bunker contains 4 inches of white sand known as ‘Best Signature’

2. Better Billy Bunker. This bunker liner is constructed as per Better Billy Bunker method. It has a gravel layer on the bunker base which is then sprayed with a polymer to form a sturdy, pliable layer of glued gravel.

• Better Billy Bunker liner depth is 2 inches
• Bunker contains 4 inches of white sand known as ‘Pro Angle’

3. Fabric-type. In this bunker system, a non-degradable synthetic material known as ‘Flexxcape’ was used instead of a hardscape. This liner is contiguous and has no overlapping edges inside the bunker base.

• Flexxcape represents a new generation of fabric-type liner
• Bunker contains 4 inches of traditional colored sand known as ‘Pioneer’

To get a better idea on bunker liners and different type of bunkers, we recommend reading an article in the July issue of the Chicago District Golfer magazine. Bunker Liners; Understanding a Trend in Course Maintenance: Innovative products assist superintendents in upkeeping pristine bunkers by Sheldon L. Solow

Bunker Surface Firmness. Recently, we collected some data on these bunkers at Bob Berry Sunshine Course to help identify differences. Surface firmness readings were taken using FieldScout TruFirm (Spectrum Technologies Inc, Aurora, IL). Data was first collected around the periphery of bunkers then in parallel lines approximately 5 feet apart to cover the whole bunker.

Figure 1. Within each sand bunker differences in firmness existed (redder colors = less firm). Trends between each sand bunker showed bunkers A and B were similar and firmer than C. This is a non-replicated study and the results of C may be influenced by site conditions. Bob Berry Course, Lemont, IL

Firmness maps for bunkers are developed using the SpecConnect mapping tool by Spectrum Technologies Inc. In these maps, a red color is less firm while green color is firm. For each of these bunkers, firmness was less around the periphery in comparison to the middle portions of the bunkers. This is possibly due to loose sand being eroded more toward the center due to slope. The differences in firmness among these bunkers could be an artifact of the different sands used. Sands can have different angle of repose. This allows different adherence of sand particles to faces of bunkers. This could have contributed to the varied firmness detected among these bunkers.

Image 1. A FieldScout TruFirm meter was used to collect data within each sand bunker. Settle, Jul 28, 2022

Bunker Surface Moisture. Moisture readings (at 1.5-inch depth) were taken using TDR350/150 (Spectrum Technologies Inc, Aurora, IL). Data was first collected around the periphery of bunkers then in parallel lines approximately 5 feet apart to cover the whole bunker.

Figure 2. Within each sand bunker differences in moisture existed (Greener colors = wetter). Trends between each sand bunker showed bunkers B and C were similar and drier than A. This is a non-replicated study and the results of C may be influenced by site conditions. Bob Berry Course, Lemont, IL

Moisture maps for bunkers are developed using the SpecConnect mapping tool by Spectrum Technologies Inc. In these maps, a red color is drier, while green color is wetter. In all bunkers, the peripheries had less moisture in comparison to the center which is probably due to the slope. There appeared to be a trend of differences among these bunkers for moisture retention.

Final Photo

Close up of panicle hydrangeas or H. paniculata in peak bloom. Settle, Aug 12, 2022