Biocontrol potential of four native entomopathogenic nematodes against Zeuzera pyrina L.(Lepidoptera: Cossidae) in the Willow trees (Salix spp.)

Abstract Background The proposal concerned with field evaluations of the four native entomopathogenic nematodes(EPNs), two Heterhabditids indica (EGAZ2 and EGAZ3) and two Steinernema carpocapsae (EGAZ9 and EGAZ10) at different concentrations (300IJs/ml, 400IJs/ml, and 500IJs/ml) against Zeuzera pyrina (Lepidoptera: Cossidae)on willow trees in the field. Results Larval mortality of Z. pyrina was measured as results of the treatments. Different nematode species and concentrations had varying effects on larval mortality. The percentage of larval mortality was increased by increasing the concentration of nematodes species. The highest mortality rate (76.8%) was recorded by the EGAZ10 strain at a concentration of 500IJs/ml. Both the nematode species and concentrations had significant effects on larval mortality. In the laboratory, larval mortality of Z. pyrina ranged between 96 and 100% all over the larval instras with EPN strains. The result showed that S. carpocapsae (EGAZ10) gave better control than the other EPN strains. Number of nematode reproductions generally increased with Z. pyrina larvae. The highest number was observed at the 6th instar larvae for the EGAZ2 strain, while the lowest number was in the 3rd instar larvae for the EGAZ10 strain. Both nematode species and larval Z. pyrina instars significantly affect the number of nematodes reproduction. Furthermore, the study investigated the nutritional content of Z. pyrina larvae and the activity of the GST enzyme when infected with the most effective nematode strain (EGAZ10). The infected larvae showed lower than protein content compared to the control, while total lipids and carbohydrates were higher than the treatments group. In addition, the treatment group’s mean GST activity was higher than the control groups. The nematodes had a destructive effect on the larvae’s metabolism, leading to physiological stress. Conclusion As obviously shown in this study, the four native species of EPNs and their concentrations had an effect on larval mortality, and differences in nematode reproduction rates. EPN species exhibited significant potency against the primary metabolites in Z. pyrina larvae, resulting in substantial disruption of intermediary metabolism due to physiological stress induced by the examined EPNs. Therefore, these EPNs species can be used as an effective tool for the Integrated Pest Management Programs (IPM) to reduce this significant pest under field conditions.