survey was carried out to determine the natural pathogens of the white grub larvae, Polyphylla adspersa (Coleoptera: Scarabaeidae) in the Mashhad region. All instar larvae of P. adspersa were collected and maintained the laboratory condition. Collected larvae cheched weekly and death larvae were transferred to the White trap. Two isolates of two nematode species were isolated from the infected larvae. Identification of these nematodes was done using morphometric and morphologic data as well SEM images. The confirmation of identification was performed using molecular data and phylogenetic analysis of ITS and 18S genes. The results showed both species belong to entomophilic nematodes of two genus Oscheius and Pristionchus. These two species including Oscheius rugaoensis Zhang et al., 2012 and Pristionchus maupasi Potts, 1910. This is first report of Oscheius genus and P. maupasi species from Iran. 0. rugaoensis had high pathogenicity and high reproductive potential. Pathogenecity of 0. rugaoensis was studied on last instar larvae of Spodoptera exigua Hubner, 1808. Oscheius species had high reproduction ability and 3-4 days after nematode inoculation, a large number of nematode progeny emerged from the cadavers while only host shell remained. On behalf of this trait, 0. rugaoensis can be consider as a potential biological control agent.

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