Labor Day! Dry, LDS, Dollar Spot Aggravates Fairways and Crabgrass Research

Just as we were winding down, summer’s heat cranked up (highs in the upper 80s) to end the final week of August. Nevertheless, summer 2022 will go down with a whimper as far as sustained heat goes. It just means the number of days with high temperatures at or above 90 degrees were few. For example, Chicago’s O’Hare Airport saw a total of 6 days above 90 degrees during July and August this year. Compare that to a hot summer like 2012 when O’Hare saw a total of 25 days above 90 degrees during the same period. What’s normal? Chicago has an average of 14 days above 90 degrees each year.

Image 1. A OO7 fairway shines during very dry conditions at Bob Berry Sunshine Course in Lemont, IL. Settle Aug 31, 2022
Figure 1. Summer 2012: A hot summer is when we rack up lots of days with highs at or above 90 degrees (and it turns out we count every one of them).

Conditions remain dry in Illinois. Our biggest issue(s) when scouting during August’s final weeks have been related to soil health. A resurgence of localized dry spot, especially in sand-based greens, was no surprise. Also, something called fairy ring can be problematic. A group of fungi that decompose thatch. A good thing. But in doing so they can damage playing surfaces. A bad thing. One issue that is silent has to do with plant physiology. Tees, fairways and greens are now tired from summer’s wear and tear. From a superintendent’s perspective the end of summer is always challenging as energy reserves of plants (carbohydrates) are largely used up. It is a time when “less is more” as far as inputs go. As we enter September, the forecast looks good. Henceforth, a surge turfgrass growth and recovery will begin. Weather-wise are set to enjoy a nice Labor Day weekend. Enjoy your holiday!

Weather Update (September begins) by Shehbaz Singh, MS

North Shore CC, Glenview. Air temperature ranged from 54 (min) to 91.9°F (max). High temperatures were mild on the weekend and ranged from 76 to 83°F. That changed markedly during the weekdays and highs ranged from 83 to 91.9°F. The highest temperature of 91.9 °F was recorded on September 1st (Thu). Heavy rainfall of about 0.6 inches was recorded on August 28th. The cumulative rainfall was 0.7 inches.

Bob Berry Sunshine Course, Lemont. Air temperature ranged from 53 (min) to 87.4°F (max). The highest temperature observed was 87.4°F on August 28th (Mon). The relative humidity ranged from 72 to 87 %. Humidity was mostly higher than the 80% during initial days of week but was lower toward the end of the week. The cumulative rainfall was 0.04 inches.

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

Dollar Spot in Fairways, Clarireedia jacksonii

We have been conducting dollar spot research in a creeping bentgrass fairway. Now is a good time to share some of those results. One observation is that dollar spot disease development has been delayed in fairways versus similar studies on a sand-based green. That is not too surprising according to one theory. The difference may be attributed to differences in native clay-loam soil’s fertility (good) versus that of sand (requires regular nitrogen inputs). Historically, we know dollar spot is a disease that can be worse in situations where nitrogen is low. However, we are beginning to see some newer research that challenges these assertions when it comes some of our common turfgrass diseases. We still have a lot to learn and we look forward to it.

Image 1. Dollar spot development in a block of 17 treatments on the right side of a L-93 fairway. Red dots are used to mark each 4 ft x 6 ft plot corner. An untreated plot is easy to differentiate from all other fungicide treatment plots. To the left outside of study is unchecked/natural dollar spot development. North Shore Country Club, Glenview, IL. Settle Aug 29, 2022
Image 2. Dollar spot development in an untreated plot in a L-93 creeping bentgrass fairway, North Shore CC, Glenview, IL. Settle, Aug 29, 2022
Figure 1. Dollar spot research on a L-93 creeping bentgrass fairway at North Shore Country Club in Glenview, IL. Fungicide treatments applied at a 21 day interval are providing desired dollar spot disease suppression. (rates used = per 1000 sq ft)

Research - Smooth Crabgrass, Digitaria ischaemum by Shehbaz Singh, MS

Biology. Crabgrass is summer annual weed that propagates through seed. Once established it is very competitive because it develops an aggressive prostrate growth habit. Smooth crabgrass is very common and has smooth leaf blades with little presences of hairs. A closely related species, large crabgrass or Digitaria sanguinalis, has hairy leaves. Smooth crabgrass has a distinct seedhead with 3–5 finger-like spikes.

Crabgrass Study Materials and Methods. A crabgrass study was conducted in a Kentucky bluegrass rough on a south-facing slope of a tee of hole number 3 at Bob Berry Sunshine Course in Lemont, IL. The study, sponsored by PBI Gordon, was initiated in June and data was collected for two months or until August. Plots were 4' by 6' and replicated 4 times in a non-randomized design. Applications were made on June 22 and July 6 using a CO2-powered backpack sprayer with flat fan nozzles. Each week the plots were evaluated for crabgrass presence, visual quality and electronic Normalized Difference Vegetation Index (NDVI). The study had four treatments (Figure 1).

Figure 1. Herbicide treatments used for a crabgrass weed control study sponsored by PBI Gordon.

Crabgrass Study Results. In this study investigated a herbicide called Q4-Plus. It contains four active ingredients. This allows for broad-spectrum weed control. One, quinclorac, is effective in selective control of crabgrass. Q4-Plus was applied alone or with adjuvants of methylated seed oil (MSO) or non-ionic surfactant (NIS). All treatments provided excellent control of crabgrass that was long lasting.

Image 1. Crabgrass control in three treatments (darker green Kentucky bluegrass) after two applications of the herbicide Q4-Plus. Crabgrass is seen within untreated and surrounding the study. Settle Aug 10, 2022
Figure 1. Crabgrass Study: Selective control of crabgrass in a Kentucky bluegrass rough, Bob Berry Sunshine Course, Lemont, IL.

Dandelion Study with Crabgrass Data. A broadleaf weed study sponsored by PBI Gordon was conducted to address dandelion. The broadleaf study was conducted in the Kentucky bluegrass rough area near green 1. Additional data was collected on crabgrass as it appeared in plots during summer.

Materials and Methods. The study was initiated in May and data was collected for three months or until August. Plots were 4' by 6' and replicated 3 times in a non-randomized design. Applications were made on May 12 alone (once) or on May 12 and June 7 (twice) using a CO2-powered backpack sprayer with flat fan nozzles. Each week the plots were evaluated for weed presence, visual quality and electronic Normalized Difference Vegetation Index (NDVI). The study had seven treatments (Figure 3).

Figure 3. Herbicide treatments used for a dandelion weed control study sponsored by PBI Gordon.

Crabgrass Data Results. As in the previous crabgrass study we found the herbicide Q4-Plus provided control of crabgrass. Other herbicides did not control crabgrass because they did not contain the active ingredient quinclorac that targets this annual, warm-season, grassy weed. Two applications of Q4-Plus were better than one application to control crabgrass.

Figure 2. Dandelion Study with Crabgrass Data: Selective control of crabgrass in a Kentucky bluegrass rough, Bob Berry Sunshine Course, Lemont, IL.

Final Photo

Goldenrod stands out in a mixed naturalized area established, in part, by controlled burns to reduce invasive woody species such as common buckthorn or Rhamnus cathartica. Bittersweet Golf Club, Gurnee, IL. Settle, Aug 30, 2022

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CDGATurfgrassProgram

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