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.
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.
Table 1:
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 | - |
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).
Table 2:
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 |
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).