Compatibility of gamma irradiation and entomopathogenic nematodes in management of the cotton bollworm Pectinophora gossypiella (Lepidoptera: Gelechiidae)

Abstract

Compatibility of gamma irradiation and entomopathogenic nematodes as a management program for management of Pectinophora gossypiella in the laboratory are a vital issue in research, but they are used as an alternative technique for insect management are still in its beginnings, Full-grown (6-days old) male pupae were irradiated with 4 sub-sterilizing doses: 30, 60, 90 and 120 Gy. The obtained results indicated the presence of an inverse relationship between the radiation doses and biological aspects of the pest where, the fecundity was decreased from 91.80 ± 56.51 to 20.8 ± 25.37 eggs/female. The mortalities in the larval population are significantly (p ≤ 0.05) increased with increasing doses as compared with the control to be 45.37, 47.37, 66.19, and 74.74% at doses of 30, 60, 90, and 120 Gy respectively, compared to 25.35% in the control group. To evaluate the compatibility and synergistic effects of gamma irradiation and EPNs in the management of Pectinophora gossypiella. Two different strains of EPNs namely Heterorhabditis bacteriophora (HB88) and Steinernema riobrave (Sr) were tested against irradiated and non-irradiated 4th larval instar and pupae of P. gossypiella. There was a positive relationship between the nematode concentrations, exposure time and mortalities of P. gossypiella. The mortality rate was 100% when 2,000 IJs were applied to both H. bacteriophora and S. riobrave. While, the low concentration (125 IJs/ml) caused 53.3 and 60% mortality after 72 h post-treatment with H. bacteriophora and S. riobrave, respectively in non-irradiated larvae. So, S. riobrave appeared to be promising in management of cotton bollworm. The combined effect of gamma irradiation with each type of entomopathogenic nematodes induced more remarkable effects on P.gossypiella as compared to gamma irradiation or each type of entomopathogenic nematodes alone.