ACTA VIROLOGICA, vol.66, no.4, pp.360-368, 2022 (SCI-Expanded)
. - The beet armyworm (Spodoptera exigua Hubner) is a polyphagous pest that causes sig-nificant economic losses and has a large host range that contains 170 plant species from 35 families in many countries. Feeding with leaves and fruits, S. exigua larvae cause plant growth to slow down and decrease, and significant crop losses. While various cultural, chemical, and biological methods are used for pest control, their effectiveness is low and the pest is still harmful to agricultural areas. In this study, we isolated two novel Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) strains from S. exigua larval cadavers collected from provinces of Igdir and Sanliurfa in Turkey, and named them SeMNPV-I and SeMNPV-U, respectively. Light microscopy confirmed that both cadavers died from baculovirus infec-tion. Scanning electron microscope observations showed that the polyhedral occlusion bodies (OBs) of the SeMNPV-I and SeMNPV-U were irregularly shaped. Transmission electron microscopy revealed that OBs of SeMNPV-I and SeMNPV-U were occupied with several virions in which multiple nucleocapsids were packaged by a viral envelope. Sequences and phylogenetic analyzes of polh, lef-8 and lef-9 revealed that these strains are closely related to baculoviruses isolates from Spodoptera species. Dose-response experiments with the isolates at 105-109 OBs/ml concentrations against S. exigua larvae led to varied mortality between 47% to 100%. The results of this study revealed that two local SeMNPV strains both have the potential to be used to control S. exigua.