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

Lymantria dispar (L.) and Dendrolimus sibiricus 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. Manduca sexta (L.) has been identified as a promising producer of DsCPV-1. Although M. sexta offers clear advantages as an alternative host for DsCPV-1 production, the DsCPV-1 isolate passaged through M. sexta (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 L. dispar (alternative host) and D. sibiricus (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 D. sibiricus larvae. In contrast, DsCPV-Ms infection of L. dispar resulted in no significant mortality despite detectable viral replication and polyhedron formation. Polyhedron formation in L. dispar 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 D. sibiricus; however, further improvements are needed before it can be applied to L. dispar.