Natural populations of Spodoptera exigua are infected by multiple viruses: implications for the production and use of virus insecticides

Abstract: Covert infections of Spodoptera exigua multiple nucleopoliedrovirus (SeMNPV) havebeen detected in laboratory or field populations of the homologous host, S. exigua. Two RNAviruses belonging to the Iflaviridae family (SeIV-1, SeIV-2) were identified in transcriptomestudies from different laboratory colonies of S. exigua. The three viruses are vertically transmitedand establish persistent infections. For this reason, coinfection of individual insects by theseviruses is considered likely. In this study, we determined the prevalence of covert infectionscaused by iflaviruses and SeMNPV in order to identify virus associations in natural S. exiguapopulations. SeMNPV was detected in the 54% of field-caught adults, whereas 13% and 8% ofinsects were infected by SeIV-1 and SeIV-2, respectively. The prevalence of SeIV-1 and SeIV-2in F1 adults obtained in laboratory showed higher levels than in the parental generation, whereasthe prevalence of SeMNPV decreased from parents to their offspring. These findings haveimportant implications for the in vivo production of virus based insecticides using mass-rearedinsects and the efficacy of these products in controling pest populations that may be coinfectedby iflaviruses.