Growing Season Finale: Cool & Cloudy, LDS, Grub Damage, and Divot Repair Research

After a long stretch of dry conditions, it finally ended. Yes, it finally rained in the Chicago suburbs this week. If you hadn’t noticed, much of September and the start of October was without rain (dry). We weren’t complaining because this uninterrupted period of good weather allowed much to be accomplished = all those “projects” at area golf courses by superintendents and staff. In the landscape fall colors continue to progress and nearly all deciduous trees are showing some color. It will take colder temperatures to bring about peak fall color in the upper Midwest. When will that happen? Historically, Chicago’s first autumn frost has occurred between September 28 (10% probability) and October 28 (90% probability). The answer is soon!

Image 1. Quick healing of aerification holes of creeping bentgrass golf greens was observed this fall. South Side Country Club, Decatur, IL. Settle, Oct 4, 2022

Weekly documentation is an important way of conveying information to growers (insert golf course superintendents here). It is meant to provide three things. 1) It captures the shifts of the seasons (and the diagnostics of associated pests). 2) It captures significant weather events. 3) It captures new and ongoing research. A Bonus) It captures the beauty of the outdoors. This will be the last edition for growing season 2022. One to remember. A good one. PS. By popular demand, the weekly reports will return next year.

2022 Weather Summary by Shehbaz Singh, MS

Here is a brief summary of the May-June weather experienced in 2022. This period was chosen because turfgrass growth is at its peak and is also when a majority of our research occurs.

  • Moderate Summer Heat — maximum air temperatures (90+ degrees F) were less than usual
  • Periods of Drought — were not long lasting in 2022
  • Flooding via large rain event(s) — location dependent; limited or did not occur in 2022
Figure 1. Weather conditions during peak turfgrass growth in 2022. North Shore Country Club, Glenview, IL

Localized Dry Spot or LDS (abiotic issue)

It would turn out that a primary issue during September and October would wind up being due to dry conditions. Called localized dry spot (LDS) and it is when soils become hydrophobic. That means it dries down to a point that it cannot rewet normally or easily. Sandy soils are more prone to LDS.

A water droplet test method can be used to help understand if a soil is hydrophobic. But there is a lot more to know. Take a look at Soil Surfactant Usage Based on Solid Science by Kostka and Fidanza.

Ways to address LDS

  • Increase frequency of irrigation — use daily hand-watering or irrigation cycles to address areas LDS-affected areas
  • Aerification by coring — thatch build-up has been linked to LDS; in the short-term holes will help water penetrate hydrophobic root zones
  • Regular wetting agent applications — standard practice to make applications every 14–28 days in sand-based root zones (golf greens)
Image 1. Localized Dry Spot in Fairway: Turfgrass is physiologically adapted to survived periods of drought by going dormant. Here’s an example of a dry down period in a creeping bentgrass fairway with native clay-loam soils. This is a newer variety of creeping bentgrass called OO7 developed with superior traits such as drought tolerance. Settle, Oct 6, 2022
Image 2. Localized Dry Spot in Green: Will have a patchy appearance, but can coalesce to become larger areas. This is OO7 creeping bentgrass in a sand-based system (golf green) where dry conditions very likely means the root zone is now hydrophobic (water-repellant). Settle, Oct 6, 2022
Image 3. Localized Dry Spot in Green: Close up of the patchy appearance that is associated with localized dry spot. Settle, Oct 6, 2022

Grub Damage (scarab beetle larvae, various)

We are in the peak period when root-feeding annual white grub damage occurs in turfgrass. Dry soils will exacerbate damage. However turfgrass is quite tolerant of root loss as long as adequate soil moisture is provided.

Ways to address Grub Damage

  • Irrigation — Water as needed/to prevent signs of turfgrass wilt
  • Map areas — Generally the same few areas are impacted year to year
  • Scout — Each year, determine if damaging populations are present in mapped areas before visual damage occurs
  • Curative Control — Broad spectrum insecticides, such as Dylox, are effective when used in spot applications. Use according to the label.
Image 1. Annual white grub damage in a Kentucky bluegrass rough. Note: Presence of animal feeding/digging is a tell-tale sign when scouting for white grub damage, Bob Berry Sunshine Course. Settle, Oct 6, 2022

Divot Repair Research Summery (Creeping Bentgrass) by Shehbaz Singh, MS

Objective. To find the appropriate divot mix for speedy divot recovery on a creeping bentgrass tee and to evaluate the effect of season on the performance or recovery potential of different divot mixes.

Location. Tee F, Piranha creeping bentgrass, Bob Berry Sunshine Course, Lemont, Illinois.

Treatments. Eleven total used.

Experimental Design. Randomized complete block design with four replications.

Three Divot Creation Events. Spring (Apr 19), Summer (Jun 23), and Fall (Sep 7). Artificially made using a divot repair tool from North Shore Country Club, Glenview, Illinois.

Weekly Data Collection. Visual quality, Normalized Difference Vegetation Index (NDVI), Visual recovery (% per divot), soil moisture and soil temperature (1.5 in depth).

Image 1. A divot repair study with three rows representing each of 3 seasons of initiation (spring = right, summer = middle and fall = left) in a Piranha creeping bentgrass tee at Bob Berry Sunshine Course, Lemont, IL. Singh, Oct 6, 2022

Spring Divot Trial Update. Initiated on April 19, during cool, wet conditions. As of October, all divot treatments show full recovery. Seed use was very beneficial. All divot mix treatments with seed outperformed its similar divot mix treatment without seed.

Poor performing divot mixes were sand only, compost only and the 8–1–1 mix only. It took more than 4 months for these treatments to show full recovery.

Figure 1. Spring initiated divot mix study in a Piranha creeping bentgrass tee at Bob Berry Sunshine Course, Lemont, IL.
Image 2. Spring Divot Trial: Recovery over time of a Piranha creeping bentgrass tee at Bob Berry Sunshine Course, Lemont, IL.

Summer Divot Trial Update. Initiated on June 23, during peak summer heat. After 3 months most treatments are showing full recovery. Earliest treatment to show full recovery was sod. It took just 1 month for sod to fully recover in summer. One divot mix treatment (compost + bentgrass seed + chewings fescue seed) showed full recovery in 1.5 months. A second divot mix treatment (8–1–1 + bentgrass seed + chewings fescue seed) showed full recovery in 2 months.

Poor performing divot mixes were sand only, compost only, and the 8–1–1 mix only. Same as was observed in spring.

Note that one treatment (compost + bentgrass seed + chewings fescue seed) performed better in the summer versus the spring. This suggests the recovery potential of this divot mix was influenced by season.

Image 2. Summer initiated divot mix study in a Piranha creeping bentgrass tee at Bob Berry Sunshine Course, Lemont, IL.

Fall Divot Trial Update: Initiated on September 7, during generally dry conditions. One treatment stood out (compost + bentgrass seed + chewings fescue seed) and showed fast recovery (~70%) after 1 week. The high moisture content in compost likely enhanced seed germination during a period of weather in the fall. A second treatment (sand + bentgrass seed + chewings fescue seed) showed good recovery (65%) after 4 weeks.

Again, seed use was very beneficial. All divot mix treatments with seed outperformed its similar divot mix treatment without seed.

In the fall, sod did not perform well when compared to spring and summer. Dry conditions in the fall predominated were the likely cause.

Image 3. Fall initiated divot mix study in a Piranha creeping bentgrass tee at Bob Berry Sunshine Course, Lemont, IL.

Final Photo

This is CDGA Turfgrass Program research in action. This mix (compost plus chewings fescue seed) was used, as needed, to fill all divots to tees on Sep 29 at Bob Berry Sunshine Course in Lemont, IL. Settle, Oct 6, 2022

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CDGATurfgrassProgram

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