September! Perfect Temps, Dollar Spot Pounces, Dry Continues, and Fall Divot Research

We made it to our first month of fall. If you closed your eyes this week outdoors you might have imaged you were somewhere else. Where the weather is perfect. When you opened your eyes you were right here — in the upper Midwest or Chicago for some of us. It meant we had made it through another bumpy growing season. We saw a bit of everything weather-wise in 2022. There were the cool, wet conditions that predominated spring. The hot, dry conditions that began summer. The periodic rainfall (perfectly timed) that meant most didn’t complain about drought. And overall, high temperatures were moderate with few days with highs at or above 90°F.

Image 1. Dollar spot hits peak pressure. A fungicide treatment stands out on a L-93 creeping bentgrass fairway at North Shore Country Club in Glenview, IL. Settle, Sep 7, 2022

Currently things in the landscape that are drought tolerant, and in flower, catch your eye. Take for example, Hylotelephium spectabile (syn. Sedum spectabile) with an appropriate variety name of ‘Autumn Joy’. In September, Honey bees are highly attracted to this plant. And on the golf course, you’ll notice the usual cultural practices have begun. This is the part of the story where we say “thank you” to greens, fairways and tees for a job well done. In particular, this aerification or “opening up” of sand-based golf greens is done to promote better root zone characteristics and leads to enhanced rooting, improved turfgrass health, establishment of thin areas, and (insert drum roll here) reduced compaction. And the list goes on. Read more here. It also means that we are already preparing for our next growing season. So get out and enjoy autumn’s perfect weather. It happens once a year in 2022.

Weather Update (Sep 1st week) by Shehbaz Singh, MS

North Shore CC, Glenview. As the week proceeded, typical fall weather began and air temperatures ranged from 56 to 80°F. September 8th represented the lowest temperature of the week (56.5°F). These lows (50s) on a consistent basis will help reduce dollar spot disease pressure. Relative humidity still remains high although soil conditions are generally dry. Early in the week relative humidity was 70-80% then rose to 80-90%. Trace rainfall of 0.07 and 0.03 inches occurred on Sep 7 and 8 respectively. Total cumulative rainfall for northern Chicago suburbs over last seven days was low. For example, 0.13 inches occurred in Glenview. Conditions are dry.

Bob Berry Sunshine Course, Lemont. Maximum temperatures experienced ranged from 83 to 88°F early then dropping to 70 to 80°F during midweek. Minimum temperatures were 53.1 to 67.4°F. Cooler night temperatures (50s) occurred for the first time. The relative humidity was around 80% early in the week with higher humidity (81-91%) on the remaining days of the week. No significant rainfall event was recorded in Lemont (0.01 inches). The cumulative rainfall for many southern Chicago suburbs remains very low. Conditions are dry.

Figures 1 and 2. Weather conditions in north and south Chicago suburbs during September, 2022.

Dollar Spot Hits Peak Pressure, Clarireedia jacksonii

Its always impressive when the weather shifts from summer to fall. Conditions can rapidly become ideal for foliar fungal disease development. Dollar spot is one example. This disease is problematic because creeping bentgrass, Agrostis stolonifera, is highly susceptible.

Image 1. Peak Disease Pressure: Current dollar spot damage in a L-93 plus Providence creeping bentgrass nursery green fungicide study. North Shore Country Club, Glenview, IL. Settle, Sep 7, 2022
Image 2. Peak Disease Pressure: Current dollar spot damage in a L-93 plus Providence creeping bentgrass nursery green fungicide study. North Shore Country Club, Glenview, IL. Settle, Sep 7, 2022

Ideal Temperatures. One reason for high dollar spot pressure now is that our low temperatures continue to remain relatively warm (60–70°F) during early September. Our low air temperatures are not yet consistently in the 50s which will naturally suppress dollar spot.

Leaf Wetness. Increased leaf wetness is now occurring. In general, a minimum duration of 10 hours of leaf wetness is required for most fungal foliar diseases. The upper Midwest represents a cool, humid climate. Heavy dew periods in the fall become a primary driver of dollar spot even though soils may be dry.

Increased Inoculum. Fungal inoculum is plentiful by the end of a growing season. Disease outbreaks tend to explode in the fall.

Fungicides. Our main way to deal with dollar spot continues to be fungicide applications applied at intervals of 14, 21 and 28 days. However, it can be frustrating during periods of high disease pressure (now). We may see that a manufacture’s label of a fungicide does not match up with our experience. We call it “break through”. A common phenomena during fall.

Cultural Practices. Our best way to deal with chronic diseases like dollar spot is to use a combination of strategies know to help suppress this disease. And there are many.

  • Judicious use of fertilizer (not too little, not too much)
  • Interrupt leaf wetness periods (early morning dew removal)
  • Light weight rolling can reduce dollar spot (5 days per week)

Creeping Bentgrass Disease Resistance. Our newest and best cultural practice strategy turns out to be dollar spot resistant cultivars. The number of new varieties that exhibit improved quality characteristics AND deliver improved dollar spot resistance is growing. We will be establishing a new nursery green variety trial in September at the CDGA’s Bob Berry Sunshine Course. We will be testing the newest creeping bentgrass varieties for dollar spot disease resistance and other positive attributes. Stay tuned.

Expert Information. Penn State’s Dr. Peter Landschoot wrote a very nice current synopsis of dollar spot that covers all the bases in 2020. It has excellent photos which are always good to see. Please click here for more.

Fall Divot Research Begins by Shehbaz Singh, MS

This week on September 6, I initiated the fall divot timing on both creeping bentgrass and Kentucky bluegrass tee studies respectively. The objective of the current study is to evaluate the impact of three different seasons on various divot treatments and their effect on turfgrass recovery. Preliminary results from both spring and summer timings suggest that certain divot mixes can vary in their ability to recover depending on the season.

Again, divots were created using a historic divot repair tool donated for use by North Shore Country Club in Glenview, IL. Divots were filled with divot mixes the same day. Each week, data is collected for visual quality, turfgrass recovery (%), Normalized Difference Vegetation Index (NDVI), soil moisture (%), and soil temperature (1.5" depth). Data collection will continue for spring, summer and fall divots until growing season end. Divot Timings: Spring = Apr 27; Summer = Jun 28; Fall = Sep 6, 2022.

Image 1. Fall Treatments: Divots are uniformly made with a tool; adjacent to summer and spring treatments (rows to the right). A Piranha creeping bentgrass tee at Bob Berry Sunshine Course, Lemont, IL. Singh, Sep 6, 2022
Image 2. Fall Treatments: Artificially created divots (1/2 inch deep) are then uniformly filled with divot mixes or are refilled with washed sod pieces. A Piranha creeping bentgrass tee at Bob Berry Sunshine Course, Lemont, IL. Singh, Sep 6, 2022
Figure 1. Spring Treatments: Results to date show a lengthy period of recovery was required for a majority of spring divot treatments in a Piranha creeping bentgrass tee at Bob Berry Sunshine Course, Lemont, IL.
Figure 2. Summer Treatments: Results to date show a faster recovery can occur for some treatments in the summer in a Piranha creeping bentgrass tee at Bob Berry Sunshine Course, Lemont, IL.

Final Photo

Honey bees are highly attracted to Hylotelephium spectabile ‘Autumn Joy’, Evanston, IL. Settle, Sep 7, 2022

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CDGATurfgrassProgram

Dedicated researchers and turf pathologists working for golf course superintendents in the Chicago area.