Impact of DsCPV-1 Passage Through Alternative Host Manduca sexta on Its Virulence, Productivity, and Transmission Potential in Lepidopteran Forest Pests

<i>Lymantria dispar</i> (L.) and <i>Dendrolimus sibiricus</i> Tschetv. are lepidopteran forest pest species, with a long history of outbreak dynamics. The recently isolated strain of Cypovirus-Dendrolimus sibiricus cypovirus-1 (DsCPV-1) shows potential as a bioinsecticide against these and other lepidopteran species. <i>Manduca sexta</i> (L.) has been identified as a promising producer of DsCPV-1. Although <i>M. sexta</i> offers clear advantages as an alternative host for DsCPV-1 production, the DsCPV-1 isolate passaged through <i>M. sexta</i> (DsCPV-Ms) produces fewer polyhedra than the original isolate. Here, we evaluated the virulence, recovery of polyhedron formation, and replication of the DsCPV-Ms in <i>L. dispar</i> (alternative host) and <i>D. sibiricus</i> (original host) larvae to assess its suitability as a biocontrol agent in these hosts. Our results demonstrate that DsCPV-Ms causes significant mortality along with efficient polyhedra synthesis in <i>D. sibiricus</i> larvae. In contrast, DsCPV-Ms infection of <i>L. dispar</i> resulted in no significant mortality despite detectable viral replication and polyhedron formation. Polyhedron formation in <i>L. dispar</i> was significantly lower following infection with DsCPV-Ms than with the original isolate, despite confirmed replication of DsCPV-Ms. These findings indicate that DsCPV-Ms remains effective against <i>D. sibiricus</i>; however, further improvements are needed before it can be applied to <i>L. dispar</i>.