August Woes: LDS, Scalp Injury, Rust Begins, and Fineleaf Fescue Research
If it seems like the days and weeks are now moving at a faster pace, it’s true. I've been counting hours of daylight. Have you? Our daylight has been decreasing since about the third week of June. My first lessons in the details of light needed for photosynthesis came from professors and Chicago’s golf course superintendents. Today, August 26, our sunrise began at 6:10 am and our sunset will happen at 7:33 pm. Since June 21, we’ve lost about an hour in the am and an hour in the pm. Add to that, the sun angle is gradually changing; shade increasingly becomes a factor as the summer season ends.
As mentioned last week, new issues are happening. Here’s three. Rust, a common fungal disease of most grasses is slowly working in older Kentucky bluegrass roughs and lawns. Faintly noticeable now, but will become more prominent in older varieties the coming months — your shoes become rust-orange. Then there’s roughstalk bluegrass or Poa trivalis. It does a summer dormancy thing. Large brown patches (temporarily) appear in fairways following extended hot, dry conditions. And finally, scalp injury of creeping bentgrass has seen a jump. Caused by a mower meeting a ‘bloated’ crown or growing point of a plant with a stoloniferous/spreading growth habit. Why intensive sand topdressing, aerification holes and verticutting are an integral part of golf green cultivation. Do listen for your superintendent’s communications. One might say, “A needed cultural practice to repair some of summer’s wear and tear is on the way.” Here’s to keeping the greens green.
Weather Update (August’s 4th Week) by Shehbaz Singh, MS
North Shore CC, Glenview. Air temperature ranged from 59 to 87°F. Highs were consistently in the 80s while lows dropped to around 60°F. The relative humidity over the last seven days ranged from 69 to 92% with driest values during midweek. Timely rainfall events were observed. Rainfall of 0.58 inches was experienced on Aug 20th (Sat) and again on Aug 25th (Thu) when 0.25 inches of rainfall was recorded. The cumulative rainfall during the period was 0.85 inches.
Bob Berry Sunshine Course, Lemont. Temperatures were a little warmer than in Glenview, but otherwise similar. Similar to the north side, weather was mild over the weekend and the high temperature recorded was 79°F. During the week days, highs were around 85°F and lows were around 55°F. Humidity tended to be higher on south side and ranged from 75 to 94%. Conditions were dry with rainfall amounts of 0.03 and 0.04 inches on Aug 20-21 (Sat and Sun) followed by a moderate rainfall event of 0.06 inches on Aug 25th (Thu). The cumulative rainfall for Lemont was a scant 0.13 inches over the last seven days.
Scalp Injury, Abiotic
Scalp Injury is a common issue of late summer that we can see with creeping bentgrass. Research has shown that without cultivation inputs (untreated) you are at a higher risk of scalp injury. Few studies have detailed scalp injury.
Nevertheless, a very good study was published by Clemson University with scalp injury data in 2007. It appeared in the Agronomy Journal. Titled Thatch and Mat Management in an Established Creeping Bentgrass Golf Green by McCarty, Gregg, and Toler. Click above link to read the entire research.
In the second year of the study, 2002, scalp injury occurred. The negative effect of scalping began in August. They were able to collect data across various cultural practices. All treatments were helpful in reducing scalp injury. Scalp injury data was captured as reduced quality when rated on a scale 1–10, 10 = best turfgrass visual quality.
- Cultivation is required when managing creeping bentgrass greens.
- Golf green cultivation practices are varied and can include: sand topdressing, vertical mowing, grooming and core aerification.
- A combination of cultivation methods are typically used to produce a healthy creeping bentgrass green.
- A surface that does not scalp is one benefit of golf green cultivation.
Rust, Puccinia and Uromyces
Rust fungal diseases affect all turfgrass species. This disease is associated with turfgrass in the late summer and fall. Also needed are stressful growing conditions. Drought stress is one example = happening now in Illinois. Rust weakens turfgrass plants and this often leads to further negative issues.
Symptoms. On leaf blades, pustules form which contain a type of spore called urediniospores. The color of these spores gives this fungal disease the common name of rust. Colors include yellow, orange, brownish yellow, chestnut brown and brick red.
Wilt. Turfgrass with rust infections most often appears thin and wilted. Part of the wilting is caused by the fungus itself. The pustules or uredinia must first rupture through a leaf’s epidermis to release spores. End result, turfgrass leaf blades are shredded by rust pustules. During dry conditions, Kentucky bluegrass roughs and lawns with rust damage will quickly wilt from excessive loss of moisture.
Control. The best cultural practice is to use newer rust-resistant cultivars.
- Use resistant varieties of Kentucky bluegrass in roughs and lawns.
- Irrigation is necessary to reduce wilt stress and plant death.
- Mow regularly to interrupt development of rust pustules/uredinia.
- Clipping removal can help in situations where rust is severe.
- Reduce shade and restricted air movement whenever possible.
- Fungicides called DMI or sterol inhibitor are historically very effective.
Fineleaf Fescue Research by Shehbaz Singh, MS
At Bob Berry Sunshine Course, there are five sand mounds in an out-of-play area along hole number 1. It was designed to allow the investigation of different fineleaf fescue species and cultivars either alone or in blends. In 2020, the five mounds were seeded with differently follows:
Mound 1: Blue sheep fescue
Mound 2: Chancellor chewings fescue
Mound 3: Chicagoland Turf Ventures Blend. A 4-way blend of Reliant IV hard fescue, Azure sheep fescue, Ambrose chewing fescue and Boreal creeping red fescue
Mound 4: Scottish Links. A 4-way blend of Shadow III chewings fescue, Reliant IV hard fescue, Epic creeping red fescue, and Azure sheep fescue
Mound 5: Irish Links. A 3-way blend of Spartan II hard fescue, Jasper II creeping red fescue and Quatro sheep fescue
A few weeks ago, we investigated these mounds to check the performance of the different fineleaf fescue species. Visual quality, NDVI, visual color, percent cover, height of seedheads and length of inflorescence was collected.
Turfgrass Cover Data. Blue sheep fescue had 90% ground cover which was the highest versus others. Chancellor chewings fescue and Chicagoland Turf Ventures Blend had 67.5% and 57.5% ground cover respectively. Scottish links mound had 42.5% while Irish links mound had the lowest ground cover (3.25%). The only mound with acceptable visual quality was blue sheep fescue mound (6.0 on a 1–9 scale). Note: Visual quality ratings were primarily influenced by poor turfgrass cover caused by less than ideal irrigation uniformity on the sand mounds (not the actual seed treatments).
Seedhead Data. Chancellor chewings fescue had tallest seedheads (mean=26.75 inches) and longest inflorescence (mean=3.67 inches). Chicagoland turf venture blend and Blue sheep fescue both had seedhead heights of about 18 inches and inflorescence lengths of about 2.5 inches. Seedhead height for Scottish links was 15.25 inches and inflorescence length were 2.25 inches. Irish links was damaged due to lack of irrigation and no seedheads were present.
Aesthetic seedhead color variations
- Blue sheep fescue = gray-buff color
- Scottish links = gray-buff color
- Chancellor chewings fescue = yellow-tan color
- Chicagoland Turf Ventures Blend = silver-yellow color
Soil Moisture Data. Soil moisture maps were prepared using the Specconect mapping tool by spectrum technologies. All these mounds had lower moisture in center comparatively to the outer regions probably due to topography and soil type (each sand-based mound transitions to a native clay loam soil at its perimeter base).