During 2014-2015, a survey was carried out to determine the natural enemies of the sugar beet armyworm, Spodoptera exigua (Hübner) in the Mashhad region of northeastern Iran. Through extensive sampling, different larval stages of S. exigua with possible signs or symptoms of infection were collected from beet fields, kept in laboratory conditions, fed with fresh beet leaves, and checked daily until the emergence of parasitoids. Herein, 12 species of parasitoids, a virus: Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV), an entomopathogenic fungus: Beauveria varroae, and an entomophilic nematode, Pristionchus pacificus are reported. The parasitoids were Meteorus rubens, Microplitis rufiventris, Cotesia sp., Chelonus (Chelonus) annulipes (Braconidae), Euplectrus sp. (Eulophidae), Sinophorus nr. xanthostomus, Anomalon sp., Diadegma pulchripes, Temelucha sp. (Ichenumonidae), two species of Drino genus and Exorista sp. (Tachinidae). The body tissues of the virus-infected larvae were liquefied, swollen, and glossy with a very thin cuticle. SEM photographs of viral occlusion bodies (OBs) showed polyhedral and irregular shapes. A cross-section of an OB indicated that each virion contained multiple nucleocapsids arranged randomly within the occlusion matrix. Genetic analysis based on lef-8 and Polyhedrin gene sequences confirmed the identity of the Iranian strain as SeMNPV. The virus was transmitted vertically and horizontally. Another pathogen was Beauveria varroae, isolated from a lepidopteran insect for the first time; S. exigua was indicated as a new host for this fungus. Both pathogens are herein introduced as new records for Iran microflora. The results of the current work highlight the diversity of natural enemies on the sugar beet armyworm in Iran.
Vol. 127 • No. 5
Vol. 127 • No. 5