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Efficacy of the newly discovered entomopathogenic nematode Steinernema adamsi against Helicoverpa zea: life stage susceptibility, UV tolerance, and field performance

James Paul Glover

James Paul Glover

USDA-ARS, Southern Insect Management Research UnitStoneville, USA
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Glover, James Paul
, 
Nathan Spaulding

Nathan Spaulding

USDA-ARS, Southern Insect Management Research UnitStoneville, USA
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Spaulding, Nathan
, 
Justin George

Justin George

USDA-ARS, Southern Insect Management Research UnitStoneville, USA
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George, Justin
, 
Maribel Portilla

Maribel Portilla

USDA-ARS, Southern Insect Management Research UnitStoneville, USA
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Portilla, Maribel
, 
Gadi V.P. Reddy

Gadi V.P. Reddy

USDA-ARS, Southern Insect Management Research UnitStoneville, USA
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Reddy, Gadi V.P.
 et 
Adler Dillman

Adler Dillman

Department of Nematology, UC RiversideUSA
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Dillman, Adler
  
24 avr. 2025
Efficacy of the newly discovered entomopathogenic nematode Steinernema adamsi against Helicoverpa zea: life stage susceptibility, UV tolerance, and field performance's Cover Image
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Catégorie d'article: Research Paper
Publié en ligne: 24 avr. 2025
Reçu: 12 nov. 2024
DOI: https://doi.org/10.2478/jofnem-2025-0012
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© 2025 James Paul Glover et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1:

Stages of S. adamsi Infection in H. zea Larvae. (A) Second instar Helicoverpa zea larva showing a positive infection of Steinernema adamsi through the anus. (B) Fourth instar H. zea larva with a large EPN mat covering most of its body, indicating advanced nematode infection. The upper right inset image shows a H. zea larva with a severe infection of the head capsule by S. adamsi.
Stages of S. adamsi Infection in H. zea Larvae. (A) Second instar Helicoverpa zea larva showing a positive infection of Steinernema adamsi through the anus. (B) Fourth instar H. zea larva with a large EPN mat covering most of its body, indicating advanced nematode infection. The upper right inset image shows a H. zea larva with a severe infection of the head capsule by S. adamsi.

Figure 2:

Application of Alginate/Congo Red Encapsulated S. adamsi Nematodes on H. zea larvae in Cotton Blooms. (A) Three-day-old Helicoverpa zea larva inside a cotton bloom, demonstrating infestation conditions. (B) Detailed view of an alginate/Congo red treatment droplet applied to the dorsal surface of the larva. (C) Magnified image showing encapsulated Steinernema adamsi nematodes within the alginate/Congo red droplet.
Application of Alginate/Congo Red Encapsulated S. adamsi Nematodes on H. zea larvae in Cotton Blooms. (A) Three-day-old Helicoverpa zea larva inside a cotton bloom, demonstrating infestation conditions. (B) Detailed view of an alginate/Congo red treatment droplet applied to the dorsal surface of the larva. (C) Magnified image showing encapsulated Steinernema adamsi nematodes within the alginate/Congo red droplet.

Figure 3:

Mortality (% ± SEM) of 2nd instars of Helicoverpa. zea caused by Steinernema adamsi exposed to ultraviolet radiation in the laboratory (27°C, 75% RH). Means with different letters are significantly different via Tukey’s HSD test after a significant ANOVA, p = 0.05).
Mortality (% ± SEM) of 2nd instars of Helicoverpa. zea caused by Steinernema adamsi exposed to ultraviolet radiation in the laboratory (27°C, 75% RH). Means with different letters are significantly different via Tukey’s HSD test after a significant ANOVA, p = 0.05).

Figure 4:

Effect of Steinernema adamsi formulations from field experiments A and B on 1st instars of Helicoverpa zea in cotton (2024, Leland, Mississippi). Field experiment A (Initial efficacy test) was conducted on August 29, 2024, with an average 33°C, 62%RH and under full sun (9495/29) (U.V. AB/C) using water as the carrier agent at 10 IJs/cm2. Field experiment B (Encapsulation and UV degradation test) was conducted on September 4, 2024, with an average 34°C, 55%RH, and full sun (9289/33) (U.V. AB/C) using alginate (0.05%, w/v) and Congo red (0.02%, w/v) formulations at 50 IJs/cm2. Means with different letters are significantly different via Tukey’s HSD test after a significant ANOVA, p = 0.05).
Effect of Steinernema adamsi formulations from field experiments A and B on 1st instars of Helicoverpa zea in cotton (2024, Leland, Mississippi). Field experiment A (Initial efficacy test) was conducted on August 29, 2024, with an average 33°C, 62%RH and under full sun (9495/29) (U.V. AB/C) using water as the carrier agent at 10 IJs/cm2. Field experiment B (Encapsulation and UV degradation test) was conducted on September 4, 2024, with an average 34°C, 55%RH, and full sun (9289/33) (U.V. AB/C) using alginate (0.05%, w/v) and Congo red (0.02%, w/v) formulations at 50 IJs/cm2. Means with different letters are significantly different via Tukey’s HSD test after a significant ANOVA, p = 0.05).

Mortality (% ± SEM) of 2nd instars of Helicoverpa_ zea caused by Steinernema adamsi mutualistic bacteria Xenorhabdus hemocoel injections and oral toxicity in the laboratory (27°C, 75% RH)_

Exposure method % Mortality ± SEM
Hemocoel injections Water 5th instar
100a
0b
F(1, 4) = 69.45
P < 0.0001
Oral toxicity Water 2nd instar
35.93 ± 1.5a
2.83 ± 0.87b
F(1, 4) = 35.04
P < 0.0274

Mortality (% ± SEM) of 1st-5th instars, and pupae of Helicoverpa_ zea caused by Steinernema adamsi entomopathogenic nematode strain in the laboratory (27°C, 75% RH)_ Mean values within a column followed by the same letter are not significantly different at P < 0_05 (Tukey’s HSD test)_

EPN strain H. zea
1st instar 2nd instar 3rd instar 4th instar 5th instars Pupae
S. adamsi 75.83 ± 4.7a 74.21 ± 1.6a 79.16 ± 2.3a 100b10 ± 1.2d 36.66 ± 3.6c 0d
Water 0d 0d 0d 0d 0d
F-Value(1, 7) 353.76 62.57 166.20 1019.97 87.96 -
P-Value <.0001 <.0002 0.0001 <.0001 <.0001 -
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