Genotypic variation among Douglas-fir tussock moth nucleopolyhedrovirus (OpNPV) isolates in the western United States.

Periodic outbreaks of the Douglas-fir tussock moth (Orgyia pseudotsugata) in forests of western North America generally end with a sudden collapse due primarily to an epizootic caused by a nucleopolyhedrovirus (NPV) that occurs naturally within O. pseudotsugata populations. We genotypically characterized NPV populations from Washington State, Oregon, Idaho, New Mexico and California for the first time.