Labor Day! 1st Fall Armyworm Signs, Lance Nematodes, and Root Research

CDGATurfgrassProgram
7 min readAug 30, 2024

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Arguably one of the hottest periods of this summer was felt in the final days of August. This time around it was the end of summer and things had changed considerably following one of the wettest July periods on record. 1) An extended cool period without precipitation meant soils were no longer saturated. 2) High temperature extremes (90+ degrees) were to be short-lived. From Saturday to Tuesday with Chicago’s official highs were 91, 93, 96, 99. Peak heat challenges water management skills wherever cool season turf is grown, and is especially true of golf greens. Highly trafficked surfaces with sand-based root zones are innately prone to wilt stress given any abnormalities in rooting are exposed. And during the week some new issues did occur — damage by root-feeding nematodes for one.

Image 1. A warm season turfgrass variety trial on a tee receives water during summer’s final heat wave (90s for highs). Three months of establishment shows speed of growth. Bermudagrass is fast (left) and zoysiagrass is slow (right). Bob Berry Sunshine Course, Lemont, IL. Settle, Aug 27, 2024

In the landscape, all things have finally reached their fully blemished self. That just means our resilient trees and shrubs have seen a few bruises too. And that’s normal. From here on out, our greenscape will be on the mend with few inputs. For example most Kentucky bluegrass and fine fescue lawns will quickly recover now that regular rains have returned. And if you looked up, you may have noticed the first colors of autumn. Case in point, the clear yellow leaves of honey locust trees will soon be everywhere in Chicago’s neighborhoods. Summer is now in the rearview mirror and labor day weekend will see the return of near-perfect weather (70s for highs).

Figure 1. August’s final week saw a final blast of peak heat. Bob Berry Sunshine Course, Lemont, IL.
Figure 2. The three month temperature forecast (Sep, Oct, Nov) is leaning warmer than normal for Illinois and much of the United States. NOAA Climate Prediction Center
Figure 3. The three month precipitation forecast (Sep, Oct, Nov) is to be near normal for Illinois. NOAA Climate Prediction Center

Scouting for Insects — Fall Armyworm (Spodoptera frugiperda)

This week, a superintendent in Rockford confirmed 1st signs of fall armyworm in northern Illinois. Distinctive egg masses laid by female moths are what we scout for. Adult moths cannot overwinter and so late summer is about when they make it to states in the upper Midwest. Eggs can be found on hard structures like buildings, fences or benches. Even a flag or flagstick on a putting green hole can see fall armyworm eggs (see image).

Damage

Turfgrass damage often appears as brown or burned-out patches. This can look like dormant turf caused by drought.

2021 = Worst Recent Armyworm Outbreak in the Midwest

See Doug Richmond’s Purdue University article. Fall Armyworms: What’s Next?

2024 Recommendations? See U of I Extension — Fall Armyworm

A few points on fall armyworm from the University of Illinois Factsheet.

  • Not generally a problem in northern Illinois because egg laying occurs in late summer (August).
  • If feeding injury occurs, a threshold of three or more caterpillars per square foot should be used to justify treatment.
  • Fall armyworm is best controlled when caterpillars are 1/2” or smaller.

Finally, contact entomologist Dr. John Schepis jschepis@illinois.edu for any additional questions or concerns regarding fall armyworms in Illinois.

Image 1. Eggs are the first signs of fall armyworm. Forest Hills Country Club, Rockford, IL. Photo courtesy Dave Braasch, Aug 29, 2024

Scouting for Nematode Damage? Lance Nematodes (Hoplolaimus galeatus)

Actually there is really no good way scout for nematode damage. Sand-based putting greens are vulnerable to anything that compromises roots. The effect of high population densities of plant parasitic nematodes translates into reduced root length and biomass as well as reduced root function. Fungal root rots are known to be associated with certain nematodes like root knot and sting. Without healthy roots, the likelihood of midday wilt stress increases.

In one instance, the cause patchy wilt on a green was found to be due to high populations of lance nematodes. The associated patch of damaged Penn A-series creeping bentgrass was about the size of a dinner plate and to be expected as nematode populations are not uniform (highest densities are always aggregated spatially). A wilted area was sampled as was a nearby healthy area (a diagnostic check).

  • Wilted patch — The numbers of lance extracted from soil samples were very high (740 lance, 20 ring and 40 spiral per 100 cc soil).
  • Healthy check — Nearby, a healthy creeping bentgrass area was sampled and low nematode numbers existed (100 ring per 100 cc soil).
Image 1. Wilt damage to a creeping bentgrass green occurred during peak summer heat. The patchy symptoms were found associated with dense lance nematode populations. Settle, Aug 29, 2024
Image 2. Root health aspects without lance (left) and with dense lance nematode populations (right). Maximum root length is reduced and a healthy white color is missing = brown. Both are negative effects caused by nematode root-feeding which impairs normal root function. Settle, Aug 29, 2024
Image 3. A juvenile (J3) lance nematode associated with turfgrass damage. This population per 100 g soil totaled 740 lance (160 males, 400 females, 180 juveniles). Lance nematodes are also migratory endoparasites and actively feed both inside and outside roots. Previous research has shown about half the population is actually located inside creeping bentgrass roots and the majority are juveniles. Settle, Aug 29, 2024
Image 4. Creeping bentgrass roots were severely damaged and those that appeared functional did not have root hairs. Signs of fungal hyphae, possibly a root rot, were also apparent. Settle, Aug 30, 2024

Evaluating Azo Root to improve creeping bentgrass root health and quality. by Shehbaz Singh, MS

A study funded by Harrell’s was initiated to evaluate effects of root health in a creeping bentgrass putting green when using a liquid product called Azo Root. Azo Root contains the soil bacteria Azospirillum brasilense. Its presence can have positive root health effects. It is being conducted on ‘007’ creeping bentgrass green which was seeded in summer 2020 at the Bob Berry Sunshine Course in Lemont, IL.

Background

During the 2023 evaluation of greens at Bob Berry Sunshine Course, green number 2 was the unhealthiest green across various measurements when compared to the other two greens on the course. For example, the average root length ranged from 4.9 to 5.5 inches for this green. The front section of the green had shortest roots (4.4 to 5.1 in) compared to the middle section (4.8 to 5.6 in) and back section (4.8 to 6.2 in). Therefore, the Azo Root study was laid out in the front section of the green.

Image 1. A Harrell’s Azo Root study, using 4 ft x 6 ft plots, to evaluate turfgrass quality and root health improvement on ‘007’ green at Bob Berry Sunshine Course, Lemont, IL. Settle, May 13, 2024

Material and Methods

The Azo Root study used 6 treatments in a randomized complete block design with 4 replications. Individual plot size was 4 ft by 6 ft. All applications began on May 13 and were made every 14 or 28 days.

  • 14-Day Applications were: May 13, Jun 3, Jun 17, Jul 2, Jul 16, Jul 30
  • 28-Day Applications were: May 13, Jun 17, Jul 16, Aug 13

The green was maintained by the Cog Hill Country Club grounds team. Fungicides were not applied during the May-Aug study period with one exception. A single application of Secure at 0.5 fl oz/1000 sq occurred on May 25, 2024.

Table 1. Azo Root treatments occurred on a ‘007’ creeping bentgrass green. Bob Berry Sunshine Course, Lemont, IL

Objectives

  • Evaluate root health
  • Evaluate turfgrass health and quality
  • Evaluate any phytotoxicity

Measurements

  • Visual Quality (1–9 scale, with 6 = minimum acceptable)
  • Normalized Difference Vegetation Index (NDVI) using GreenSeeker/Trimble HCS-100
  • Localized Dry Spot (%)
  • Color/Phytotoxicity (1–9 scale, 9 = best color)-
  • Maximum Root Length (two evaluations) 1) Jul 22: used a 3/4 in soil sampler, 2) Aug 22 used a Mascaro Profile sampler
  • Root-feeding nematodes extracted by lite sucrose centrifugation using 100g soil (upper 2 inches of four soil cores)

Localized Dry Spot (LDS)

Before study start, the average localized dry spot incidence on plots was 17.5%. Trends of localized dry spot reduction was observed for some treatments. For Azo Root 0.3 oz at the 14-day interval, localized dry spot was reduced from 18.7% to 5% in the first two weeks of the study. Thereafter LDS remained lower than 10% in that 14-day treatment. In contrast, Azo Root 0.3 oz at the 28-day interval experienced more than 10% LDS on most ratings dates.

In comparison, the fungicide check Resilia 4 oz at the 28-day interval resulted in less than 10% LDS on most rating dates.

Figure 1. Localized Dry Spot of Azo Root treatments on a ‘007’ creeping bentgrass green. Bob Berry Sunshine Course, Lemont, IL

Visual Quality

Turf quality of Azo Root 0.3 oz every 14 days and Resillia 4 oz every 28 days was higher than the minimal acceptable limit (6.0) on most rating dates. In contrast, Azo Root 0.3 oz every 28 days was unacceptable on a majority of rating dates.

Figure 2. Visual Quality of Azo Root treatments on a ‘007’ creeping bentgrass green. Bob Berry Sunshine Course, Lemont, IL
Image 2. Visual Quality of Azo Root treatments on a ‘007’ creeping bentgrass green. Primary visual differences during the study were caused by localized dry spot, Bob Berry Sunshine Course, Lemont, IL. Singh, Jul 23, 2024

Maximum Root Length

Subtle differences in maximum root length were observed when measured on two dates in summer. In late August, the 14 day application interval of Azo Root 0.3 fl oz tended to outperform the 28 day interval.

Figure 3. Maximum Root Length of Azo Root treatments on a ‘007’ creeping bentgrass green in 2024. Bob Berry Sunshine Course, Lemont, IL
Image 3. Maximum Root Length of Azo Root treatments on a ‘007’ creeping bentgrass green in 2024, Bob Berry Sunshine Course, Lemont, IL. Settle, Aug 22, 2024

Nematodes

Ring , stubby root, and root-knot nematodes were present and uniformly distributed. Lance were also present (data not shown). Populations were located only on the left side of the green and densities were low (20–240 per 100 g soil). Overall, nematode numbers were low to moderate and would not be impactful to root health.

Figure 4. Average Nematode Numbers (per 100 g soil) in Azo Root treatments on a ‘007’ creeping bentgrass green (average represents 4 replicates sampled on July 23, 2024). Bob Berry Sunshine Course, Lemont, IL

Final Image

Goldenrod is a common flowering forb in native prairies, Glencoe, IL. Settle, Aug 21, 2024

Solidago, commonly called goldenrods, is a genus of about 100 to 120 species of flowering plants in the family Asteraceae. Most are herbaceous perennial species found in open areas such as meadows, prairies, and savannas. They are mostly native to North America, including Mexico; a few species are native to South America and Eurasia. Some American species have also been introduced into Europe and other parts of the world.” For more see Solidago — Wikipedia

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CDGATurfgrassProgram

Written by Derek Settle, PhD & Shehbaz Singh, MS. Mission: Provide science-based turfgrass research and diagnostics to 400+ member golf courses/superintendents.