Drought Returns! Dry, ABW Again, White Grubs, Armyworms, and Tenacity Research

Who knows a good rain dance? The plan to wait, or to ask nicely is now over. This week, cool season turfgrass in the urban landscape and in golf roughs was showing stress. Without irrigation, a majority are now varying shades of brown (dormant turf is okay and normal). However, areas which experience deep shade under trees (fine fescue is best adapted) will definitely require renovation in 2024. The US Drought Monitor saw an update and several midwestern states are now seeing levels of drought which range from moderate to exceptional. Moderate drought (D1) is now occurring in southern Illinois, and severe drought (D2) is being reported in southern most areas of Missouri, Indiana and Kentucky. Hardest hit? Southeastern Ohio is experiencing extreme to exceptional (D3-D4) drought. Even Chicago’s suburbs have begun to see a few areas of moderate drought.

Image 1. A granular spoon-feed fertilizer application (0.2 lbs N per 1000 sq ft) is watered in during early morning hours. A Penn A1 plus Penn A4 green gets some fuel. Twin Orchard Country Club, Long Grove, IL. Settle, Sep 12, 2024

Not surprisingly, drought can impact the timing of deciduous tree fall color. Moderate drought can delay fall color development (Chicago’s senario), whereas severe drought can speed things up or you’ll not see any at all (SE Ohio’s senario). On golf courses this week, issues were all root- or soil-related. Here’s a few. 1) A dramatic loss of roots and associated turf damage would be quickly noticed (annual white grubs). 2) Increasing amounts of localized dry spot became apparent (associated with hydrophobic or water-repellent soils). 3) Other non-uniform patterns began to frustrate, “It looks like an alligator’s back!” (a grid of mower scalp injury the size of dinner plates in creeping bentgrass fairways). Superintendents are now using deeper cycles of irrigation, as well as regular applications of wetting agents to help overcome this and more. Meanwhile, golf playing conditions remain terrific. Without precipitation, “hard and fast” is the new norm.

Weather

Figure 1. September sees the return of heat which may be impactful for the insect pests we are now scouting for (annual bluegrass weevil, white grubs, and armyworms). Bob Berry Sunshine Course, Lemont, IL

Figure 2. Drought is currently progressing in the upper Midwest region. Courtesy U.S. Drought Monitor

Scouting for Insects— Annual Bluegrass Weevil (Listronotus maculicollis)

Another case of annual bluegrass weevil (ABW) was reported and confirmed this week in Chicago’s north suburbs. ABW locations impacted are officially in the double digits for Illinois.

Recent ABW Reports in Wisconsin

On Aug 29, 2024, Dr. Paul Koch and Kurt Hockemeyer reported two more golf courses with ABW. Interestingly, it had been four years since the first report of ABW at a golf course in Wisconsin. All are located in central Wisconsin.

University of Illinois Pesticide News — Emergence of a new Illinois turf pest: The annual bluegrass weevil

Entomologist, Dr. John Schepis, has created an update for this new pest of Illinois. Click the link to view the full publication.

“Infestations of the domestic turf pest, annual bluegrass weevil (ABW), Listronotus maculicollis, have officially been identified in Northern Illinois. Historically, this insect has been a pest in highly managed turf in Mid-Atlantic states and has recently been infesting new states throughout the Midwest. In 2023, ABW infestations were identified in Illinois for the first time in two North Chicago golf courses…”

Image 1. Sampling for annual bluegrass weevil larvae in a creeping bentgrass/annual bluegrass fairway. Only annual bluegrass suffered damage caused by root feeding of larvae/grubs. Bentgrass remained healthy. Settle, Sep 11, 2024

Figure 2. ABW damage can be easily confused with other diseases and issues of annual bluegrass such as summer patch. Settle, Sep 11, 2024

Table 1. A total of 10 golf courses in the Chicago area now have confirmed cases of annual bluegrass weevil.

Scouting for Insects — Annual White Grubs of Japanese beetles (Popillia japonica), northern masked chafers (Cyclocephala sp.) and others

Unfortunately it is animal digging that causes the majority of damage when high populations of annual white grubs (beetle larvae) happen to be feeding on turfgrass roots. In one instance this week the culprit was obviously a skunk or two. Pew

Image 1. A damaged Kentucky bluegrass lawn is investigated. Initial damage would have been caused by midday wilt stress due to root loss (white grub feeding). Final physical disruption was by animals. Damage by skunks, this case, is a much greater issue and why curative grub control was necessary. Settle, Sep 9, 2024

Image 2. Turf pulls back easily due to a lack of roots. The cause, feeding white grubs, is found. A damage threshold of 12 grubs per square foot can be used for curative treatments. Settle, Sep 9, 2024

White Grub — Illinois & Managing White Grubs in Turfgrass — Indiana

Excellent fact sheets on annual white grubs exist for our region. For everything you need to know, see links above.

Scouting for Insects — Fall Armyworm (Spodoptera frugiperda)

This week a Chicago golf course superintendent found the tell tale signs of armyworm (adult moth eggs). It coincided with good information from Purdue University which has implications for turfgrass managers in both Indiana and Illinois. It detailed that treatments are likely not necessary in northern Illinois. However, southern portions of both states are at risk for fall armyworm damage.

September 12, 2024: Fall Armyworms, Again? by Dr. Doug Richmond, Purdue University

“Given the late starting date of this outbreak, we are unlikely to see another generation of fall armyworm larvae, but turf managers in the southernmost areas of the state should be vigilant through early October.” See link above.

Image 1. Scouting for egg masses (lower left corner of a golf green flag) is a good way to monitor for fall armyworm. The pest is now in the Chicago area. Courtesy Chicago GCS, Sep 9, 2024

Tenacity Herbicide for Selective Removal of Creeping Bentgrass from Kentucky Bluegrass by Shehbaz Singh, MS

In 2023, a herbicide study sponsored by Syngenta was conducted on three tees at Bob Berry Sunshine Course in Lemont, IL. Results from two Kentucky bluegrass tees will be updated and discussed. A RTF tall fescue tee saw similar results but will not be presented.

Image 1. Tee A was regrassed to ‘HD Sports 2.0’ Kentucky bluegrass in 2020, but had previously been creeping bentgrass. Kentucky bluegrass was quickly recontaminated with bentgrass. The first of three tee study sites that explored Tenacity herbicide as a way to selectively remove creeping bentgrass at Bob Berry Sunshine Course in Lemont, IL. Singh, Sep 12, 2024

Image 2. Tee B was regrassed to ‘HGT’ Kentucky bluegrass in 2020, but had previously been creeping bentgrass. Kentucky bluegrass was quickly recontaminated with bentgrass. the second of three tee study sites that explored Tenacity herbicide as a way to selectively remove creeping bentgrass at Bob Berry Sunshine Course in Lemont, IL. Singh, Sep 12, 2024

Tee A and B Background

Both were originally ‘Penncross’ creeping bentgrass (2004–2020). In 2020 an extensive renovation of Bob Berry Sunshine Course converted creeping bentgrass tees to Kentucky bluegrass using two steps. The nonselective herbicide glyphosate was applied to the creeping bentgrass surface and the dead turf was later removed by a sod cutter. A 2022 evaluation of tee surfaces revealed up to 80% contamination of Kentucky bluegrass by creeping bentgrass. Within 3 years of tee renovation, the original creeping bentgrass had found its way back and was aggressively displacing the desired Kentucky bluegrass.

Objectives

• Evaluate Tenacity for selective removal of creeping bentgrass
• Evaluate regrowth of Kentucky bluegrass

Material & Methods

Both studies were conducted using a randomized complete block design with 4 replications. Three treatments were used. Individual plots were large and measured 5 ft x 10 ft. Treatments were applied using a CO2 backpack sprayer operated at 40 psi; three nozzles with XR TEEJET 800VS. Applied in water equivalent to 2 gal per 100 sq ft. A total of 2 or 3 applications were made. Tenacity was mixed with a non-ionic surfactant (NIS) at the rate of 0.25% by volume.

To promote regrowth of Kentucky bluegrass, liquid urea was applied six times at a rate of 0.25 lbs N/1000 sq ft bi-weekly following the second application date on Sep 12, 19, 26, and Oct 3, 10, 17 in 2023.

Table 1. Treatments used in the Tenacity study at Bob Berry Sunshine Course in Lemont in 2023.

Data

• Visual Quality (1–9 scale, with 6 = minimum acceptable and 9 = best)
• Normalized Difference Vegetation Index (NDVI) using GreenSeeker/Trimble HCS-100
• Creeping Bentgrass and Kentucky Bluegrass (% per plot)
• Transitional Brown Turfgrass (% per plot)
• Phytotoxicity (% per plot)

Creeping Bentgrass Contamination — HD Sport 2.0 Kentucky Bluegrass Tee

• Study Start: Contamination by creeping bentgrass was 78.8%
• Six months: Bentgrass had been significantly reduced by Tenacity. For example, two applications 14 days apart resulted in 5% creeping bentgrass and three applications 14 days apart resulted in 1.75% creeping bentgrass.
• Sep 3, 2024 ~one year later: A year later, creeping bentgrass saw regrowth in treated plots. Two applications 14 days apart resulted in 18.7% creeping bentgrass and three applications 14 days apart resulted in 8% creeping bentgrass.

Figure 1. Creeping bentgrass contamination in a Kentucky bluegrass tee given 2 or 3 Tenacity applications in 2023. Actual dates were Aug 22 and Sep 6 (2 apps.) or Aug 22, Sep 6 and Sep 19 (3 apps.). Bob Berry Sunshine Course, Lemont, IL

Figure 2. Kentucky bluegrass regrowth in a tee contaminated with creeping bentgrass given 2 or 3 Tenacity applications in 2023. Actual dates were Aug 22 and Sep 6 (2 apps.) or Aug 22, Sep 6 and Sep 19 (3 apps.). Bob Berry Sunshine Course, Lemont, IL

Image 3. ‘HD Sport 2.0’ Kentucky Bluegrass block 1 plots measuring 5 ft x 10 ft showing untreated (with creeping bentgrass) versus Tenacity treatments with low levels of remaining creeping bentgrass contamination. Singh, Sep 12, 2024

Creeping Bentgrass Contamination — HGT Kentucky Bluegrass Tee

• Study Start: Contamination by creeping bentgrass was 87%
• Six months: Bentgrass had been significantly reduced by Tenacity. For example, two applications 14 days apart resulted in 3% creeping bentgrass and three applications 14 days apart resulted in 1.5% creeping bentgrass.
• Sep 3, 2024 ~one year later: A year later, creeping bentgrass saw regrowth in treated plots. Two applications 14 days apart resulted in 20% creeping bentgrass and three applications 14 days apart resulted in 4.25% creeping bentgrass.

Figure 3. Creeping bentgrass contamination in a Kentucky bluegrass tee given 2 or 3 Tenacity applications in 2023. Actual dates were Aug 22 and Sep 6 (2 apps.) or Aug 22, Sep 6 and Sep 19 (3 apps.). Bob Berry Sunshine Course, Lemont, IL

Figure 4. Kentucky bluegrass regrowth in a tee contaminated with creeping bentgrass given 2 or 3 Tenacity applications in 2023. Actual dates were Aug 22 and Sep 6 (2 apps.) or Aug 22, Sep 6 and Sep 19 (3 apps.). Bob Berry Sunshine Course, Lemont, IL

Image 4. ‘HGT’ Kentucky Bluegrass block 1 plots measuring 5 ft x 10 ft showing untreated (with creeping bentgrass) versus Tenacity treatments with low levels of remaining creeping bentgrass contamination. Singh, Sep 12, 2024

Final Image

Little bluestem ‘Standing Ovation’ makes a statement in a mixed native grass feature and nicely separates a driving range from a tee at Skokie Country Club, Glencoe, IL. Settle, Sep 12, 2024

“Little bluestem is a perennial bunchgrass and is prominent in tallgrass prairie, along with big bluestem (Andropogon gerardi), indiangrass (Sorghastrum nutans) and switchgrass (Panicum virgatum). It is a warm-season species, meaning it employs the C4 photosynthetic pathway.

A number of cultivars have been developed. ‘Carousel’ is a compact form with especially good fall color developed by Chicagoland Grows. ‘The Blues’ is a selection that has bluer foliage. ‘Standing Ovation’ is a tight, upright form with bluer and thicker blades and sturdier stems.” For more see Schizachyrium scoparium — Wikipedia