Determining the Pathogenicity of Symbiotic Bacteria of Entomopathogenic Nematodes against the Larvae of Tobacco Caterpillar (Spodoptera litura F.)

This chapter investigate the bacterial pathogenicity of symbiotic bacteria against the serious insect pest that feeds voraciously on both agricultural and horticultural crops, Spodoptera litura.

Spodoptera litura Fabricius (Lepidoptera: Noctuidae) an economically important insect pests worldwide, especially in the tropics, temperate zones, and other warm environments. In this investigation symbiotic bacteria of entomopathogenic nematodes were evaluated for their insecticidal activity against larvae of S. litura under lab conditions. The four new isolates (EPB1, EPB4, EPB8 and EPB9) belongs to Photorhabdus luminescence isolated from nematode Heterorhabditis bacteriophora and one isolate (EPB3) of Xenorhabdus nematophila isolated from nematode Steinernema sp. were used in the study. The intact cell suspension and cell-free extract were screened for their bacterial pathogenicity and the results showed mortality of larvae after 24h of post treatment. The percent mortality treated with intact cell suspension was significantly higher CFU with a median lethal time ranging from 33-45h. The results showed that the isolates EPB3 (Xenorhabdus nematophilus) is comparatively more virulent than other Photorhabdus isolates against the test insect S. litura. This study paves the way for advances in our understanding of the virulence of several Entamopathogenic bacteria in non- model insects, such as the new invasive S. frugiperda species in Africa.

These symbiotic bacteria can also be produced as potential biopesticides against insect pests by screening them for their biocontrol effectiveness in greenhouse and field settings.