Potential Use of the Saltmarsh Caterpillar as a Production Host for Nucleopolyhedrosis Viruses1

Abstract
The virulence of the nucleopolyhedrosis viruses (NPVs) of Douglas fir tussock moth, Orgyia pseudotsugata (McDunnough), spruce budworm, Choristoneura fumiferana (Clemens), and gypsy moth, Lymantria dispar (L.), for larvae of the saltmarsh caterpillar, Estigmene acrea (Drury), was enhanced after successive passage in the alternate host. In all cases, yields of 2 × 109 polyhedral inclusion bodies were obtained per E. acrea larva, which represented at least a fourfold increase in O. pseudotsugata and C. fumiferana NPVs obtained from the respective natural hosts. The O. pseudotsugata-NPV-E. acrea system appears to be an excellent system for production of Douglas fir tussock moth NPV on the basis of both virus yield and activity. The C. fumiferana NPV-E. acrea and L. dispar NPV-E. acrea systems appear less promising on the basis of virus activity.