Plaque assay for Spodoptera exigua and Autographa californica nuclear polyhedrosis viruses in a newly established cell line of the beet armyworm, Spodoptera exigua.

The nuclear polyhedrosis viruses of Spodoptera exigua (SeNPV) and Autographa californica (AcNPV) produced plaques in a newly established cell line of the beet armyworm, Spodoptera exigua. Plaques were composed of infected cells containing many polyhedra and were visible without any staining procedure. Dose-response assays showed a direct correlation between the number of plaques and the inoculum size. Growth kinetic studies of the two viruses, using the developed plaque assay system, revealed that the release of extracellular viruses began 6 hrs post infection (p.i.) and the titer reached a plateau 48 hrs p.i. The sensitivity of this plaque assay system was 100 times greater for the heterologous AcNPV than for the homologous SeNPV.