100 Degrees! Annual Bluegrass Weevil, Pythium Blight, and Fairway Research
It hit 100! Record heat would grip a majority of the country during August’s third week. Billed as “Summer’s Hottest Spell”, it tested many things including cool season turfgrass. It did not last long, but this late round of summer heat got our attention. Excessive heat watches and warnings were declared for Wednesday (~99 degrees) and (~100 degrees) Thursday. Those Chicago high temperatures tied records that date to 1947. It tells us late summer heat of this magnitude is uncommon. Just another reminder that growing season 2023 has been consistently inconsistent — what I now say.
Just about every aspect of the landscape looks tired (as it should). But even at summer’s end, new things appear. For example, goldenrod began to bloom this week. Up next = a silver lining for turfgrass managers as our short-term forecast is calling for a cool period (highs no greater than 70s in Chicago). In a cool, humid environment, those temperatures represent a return to what nearly everything is well adapted for. Once again, the driver’s seat belongs to photosynthesis (energy production). A period of optimum growth (and rapid recovery) will now begin. Watch how quickly thinned lawns and golf course roughs can recover in the next month or so. Kentucky bluegrass is like the David Copperfield of turfgrass. It has magic when it comes to recuperative potential. Rhizomes! What you can’t see belowground creates a big advantage at summer’s end versus other species.
Annual Bluegrass Weevil, Listronotus maculicollis
This insect is commonly referred to as ABW. It is only a problem in turfgrass maintained at low mowing heights (0.5 inch or less). This means it is a unique problem for golf courses. Fairways, tees, green collars and green surrounds are vulnerable to damage. Higher heights of cut (roughs or home lawns) are not impacted.
Found in Illinois
Previously the annual bluegrass weevil did not exist in Illinois. This week a Chicago golf course with annual bluegrass was found to have annual bluegrass weevil larvae and adults. In this case only a portion of a collar of a few greens were negatively impacted. The actual green surface was not affected — required daily mowing (and clipping removal) protects greens from ABW establishment and damage.
The annual bluegrass weevil was originally detected in Long Island, New York in 1957. It’s early spread (1957-1970s) was closely tracked and ABW was thereafter found in the states of New York, Massachusetts, Rhode Island and Pennsylvania. Today, it continues to spread slowly and has now been identified in several more states as well as territories in Canada. Primary mode of introduction is the transport of infested sod containing ABW.
- Root Loss. Turf damage is caused by root loss via active feeding of the insect larvae (grubs). Adult feeding is not important.
- Three Generations. By the end of August, further ABW infestations are unlikely — the end of summer represents the third and final generation.
- Newer Insecticides. Newer options exist and their use lessens risk of insecticide resistance by ABW. This is important because certain chemistries (e.g., pyrethroids like bifenthrin) are known to be problematic. Rotation of different chemical classes of insecticides is key in the management of ABW.
- Application Timings for ABW. Timing is important and has been attained using growing degree day (GDD) models. For example, first insecticide application is in the spring when overwintering adults become active (~April in Chicago).
- Plant Phenology Timing for ABW. In the spring can also use plant development indicators. First spring application for ABW would coincide with Boarder Forsythia bloom when it is 1/2 yellow (just past peak bloom) and 1/2 green (as it begins to leaf out).
ABW Recently Confirmed in Several States
PennState Extension Annual Bluegrass Weevil — Annual bluegrass weevils present a serious problem for golf course superintendents. May 2, 2022. Ben McGraw and Danny Kline.
University of Wisconsin TDL New Pest Alert: Annual bluegrass weevil has been found in Wisconsin Kurt Hockemeyer and Paul Koch. 2020.
Best Management Practices for New York State Golf Courses Spring ABW Management May 2, 2022. Ken Benoit.
Turfgrass Insects of the United States and Canada, Second Edition. 1999. Patricia J. Vittum, Michael G. Villani, Haruo Tahsiro
Pythium Blight (Pythium aphanidermatum)
One more sign of record heat you ask? Pythium blight which requires high temperatures was reported by a Chicago-area superintendent this week. It followed a string of 90+ degree days.
Appears as sunken, greasy black patches and streaks. Creeping bentgrass can have a unique reddish-orange color. Patches appear circular a few inches in diameter. Affected turf quickly becomes matted and leaf blades will have a water-soaked appearance. Leaf lesions are absent. Pythium blight is a rapid disease and can kill turfgrass in 24 hours. White, cottony mycelium may be present in the morning just after infection.
- Hot. high temperatures of 85–100 degrees
- Wet and Saturated. either by rainfall or heavy periods of dew
Pythium is more closely related to brown algae and so its control goes beyond the traditional fungicides we use. It requires specific chemistry. Preventive control of Pythium has gotten better in recent years as newer products are now available. Two examples are Segway and Serrata. They add to the existing Pythium specialists of Banol and Subdue MAXX. Greater control efficacy has been achieved by integrating these newer products. It has also improved our ability to rotate chemistries (helps reduce the risk of fungicide resistance).
Chemical Control of Turfgrass Diseases 2020 See Pythium Blight (page 25).
Fairway Research — August 23, 2023 by Shehbaz Singh, MS
As a part of monthly evaluation of greens, fairways, and tees at Bob Berry Sunshine Course, all fairways were evaluated this week.
Investigations evaluate playability, agronomic characteristics and quality. There are total of four creeping bentgrass fairways with different varieties*. *Fairways were renovated in 2020 by Wadsworth Golf Construction Co.
- Fairway 1: Crystal Bluelinks, 17,377 sq ft
- Fairway 2: OO7, 10,254 sq ft
- Fairway 3: Pure Select, 8,089 sq ft
- Apron: Pure Eclipse, 2,000 sq ft
On each fairway, three points were selected in a systematic way using a straight center line in front (approach), middle, and back. Four data readings or samples were collected around each of the three marked points. Six sets of data were collected (see below).
- Visual Quality (1–9 scale with 9 best and 6 = minimum acceptable)
- Normalized Difference Vegetation Index (NDVI) was measured using GreenSeeker by Trimble.
- Soil Moisture was measured using TDR350 by Spectrum Technologies, Illinois.
- Surface Firmness was measured using Field Scout TruFirm by Spectrum Technologies, Illinois.
- Shear Strength was measured using Shear Tester by Turf-Tech International, Florida.
- Weeds (%) was visually estimated around each point in about area of a 5 ft radius circle.
- Localized Dry Spot (%) was visually estimated around each point in about area of 5 feet radius circle.
- Root Length was measured taking the average of four 0.5-inch diameter soil core samples (maximum root length)
- Thatch Layer (cm) was measured taking the average of four 0.5-inch diameter soil core.
- Root-Feeding Nematodes were extracted by lite sucrose centrifugation using 100g soil (upper 2-inches of four soil cores). Four samples or data readings were collected around the point for each parameter.