Aerial Applications of a Nucleopolyhedrosis Virus and Bacillus thuringiensis Against the Douglas Fir Tussock Moth12

Efficacy of applications of a nucleopolyhedrosis virus (NPV) and Dipel (Bacillus thuringiensis Berliner) against Orgyia pseudotsugata (McDunnough) was determined on replicated field plots of 20 acres in size. Population reductions exceeded 95% at 35 days on plots treated with NPV dosages of 100×109 and at 100×1010 polyhedra/acre in 2 gal/acre of a 25% molasses formulation. Application of Dipel at 1 lb/acre in 25% molasses was as effective as the NPV. These treatments also provided excellent foliage protection, with estimated defoliation levels below 25%. In contrast, Dipel formulated in BioFilm® failed to reduce larval densities to a satisfactory level or to prevent severe defoliation.