Baculovirus
Insects are infected by 20 virus families including the Baculoviridae virus family. Two genera within the Baculoviridae (Granulovirus (GV) and Nucleopolyhedrovirus (NPV)) have attracted much interest as potential agents for use in suppressing forest insect pest populations. The Baculoviridae are attractive because they are restricted to arthropods, primarily to insects, they are host specific, and many are known to cause sudden and severe disease outbreaks (epizootics) within host populations. For example, population crashes because of NPV epidemics occur in many species of sawflies (Hymenoptera: Diprionidae) and similarly in several species of forest Lepidoptera, including the Douglas-fir tussock moth (Orgyia pseudotsugata), the whitemarked tussock moth (O. leucostigma), and the gypsy moth (Lymantria dispar).
Diagram of a NPV life cycle (from From Wikipedia)