The greater wax moth, Galleria mellonella, is a significant pest in apiculture and a well-established model organism for immunological and ecotoxicological studies. This investigation explores the individual and combined effects of the ectoparasite Bracon hebetor (B.h.) and the entomopathogenic nematode Steinernema carpocapsae (S.c.) on G. mellonella larvae. We evaluated the activity of oxidative stress enzymes, including superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione S-transferase (GST), malondialdehyde (MDA) levels, cytochrome P450 activity, cell viability using Annexin V-FITC, DNA damage via comet assay, and larval morphology through scanning electron microscopy (SEM). Control larvae exhibited higher GPx and GST activities compared to those treated with B.h., S.c., or the B.h. + S.c. combination. Conversely, MDA levels displayed the opposite trend. SOD activity was reduced in the B.h. and S.c. groups but significantly higher in the combined treatment. Cytochrome P450 activity increased in response to parasitism by B. hebetor. The Annexin V-FITC assay revealed decreased cell viability in parasitized groups (B.h. 79.4%, S.c. 77.3%, B.h. + S.c. 70.1%) compared to controls. DNA damage analysis demonstrated significant differences between groups, and SEM observations confirmed severe cuticle abnormalities or malformations in G. mellonella larvae. These findings highlight the complex interactions between B. hebetor, S. carpocapsae, and their host, G. mellonella. Additionally, they illuminate the intricate physiological responses triggered within the host larvae.

The integration of chemical insecticides with the biocontrol agent, entomopathogenic nematodes (EPNs) belonging to the Heterorhabditidae family, necessitates an understanding of the potential adverse effects of these insecticides on the biocontrol agent. Therefore, the primary objective of this research was to investigate the impact of two organophosphates (profenofos and chlorpyrifos), a carbamate (methomyl), and two pyrethroids (lambda-cyhalothrin and deltamethrin) on the viability and virulence of three strains of EPNs: Heterorhabditis sp. NEM 08, Heterorhabditis sp. NEM 15, and Heterorhabditis bacteriophora HP88. This investigation involved assessing their action on viability and infectivity toward the last instar larvae of Galleria mellonella upon exposure to recommended field rates for varying durations: 6 hours, 24 hours, and 48 hours. The results concerning EPN viability revealed that profenofos caused the most significant reduction in EPN viability, ranging from 44.9% to 65.9% after 48 hours of exposure. Additionally, the EPN strains exhibited varying levels of tolerance. Profenofos also had the highest adverse impact on infectivity, resulting in reductions ranging from 65.9% to 82.2% after 48 hours of exposure. Chlorpyrifos followed, which causing reductions in infectivity ranging from 25% to 55.6% after 48 hours of exposure. In contrast, Lambda-cyhalothrin had the least adverse effect on EPN viability and infectivity. Furthermore, it was observed that prolonged exposure time intensified the adverse effects on EPN viability and infectivity. These findings provide valuable insights for the integrated use of these neurotoxic insecticides with EPNs in insect control programs, helping in the selection of the most tolerant EPN strains for this purpose.