In-Vitro Pathogenicity of Entomopathogenic Nematodes Associated Symbiotic Bacteria and their Metabolites against Armyworm Spodoptera litura Fabricius
In-Vitro Pathogenicity of Entomopathogenic Nematodes Associated Symbiotic Bacteria and their Metabolites against Armyworm Spodoptera litura Fabricius
Hina Safdar1,2*, Nazir Javed2, Sajid Aleem Khan2, Muhammad Zeeshan Majeed3, Arif Mehmood3 and Muhammad Arshad4
ABSTRACT
Entomopathogenic nematodes (EPNs) are effective biocontrol agents against different insect pests. However, very little work has been done in Pakistan on the symbiotic bacteria associated with EPNs and their metabolites. In this laboratory study, two bacterial isolates i.e. Xenorhabdus spp. associated with EPN Steinernema glaseri (Steiner) (Steinernematidae) and Photorhabdus spp. associated with EPN Heterorhabditis bacteriophora (Poinar) (Heterorhabditidae), were evaluated against armyworm Spodoptera litura Fabricius (Lepidoptera: Noctuidae) which is a destructive lepidopterous pest. These EPNs associated bacterial isolates were applied @ 4×107 CFUs/mL against different larval instars of S. litura. At day one post-treatment, maximum larval mortality (59.40%) was exhibited by Xenorhabdus spp. against 2nd instar larvae followed by 52.80, 46.20 and 46.20% mortality of 5th, 3rd and 4th instar larvae, respectively. In case of Photorhabdus spp., maximum mortality (26.40%) was observed against 2nd instar larvae. In other bioassay, 40% suspensions of bacterial metabolites were evaluated against different larval instars of S. litura and were found significantly effective against all larval instars. Maximum average mortality (52.80%) was observed in Xenorhabdus spp. derived metabolites against 2nd instar larvae as compared to Photorhabdus spp. In both bioassays, mortality was increased along with the exposure time and reached 100% in all S. litura larval instars at fourth day post-treatment. Findings of this in-vitro study demonstrate that EPNs and their symbiotic bacterial isolates would be effective biorational control tools against S. litura.
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