Labor Day! 1st Fall Armyworm Signs, Lance Nematodes, and Root Research
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.
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).
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.
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).
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.
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.
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.
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.
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.
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.
Final Image
“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
