Nucleopolyhedrovirus pathology in spruce budworm larvae

Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae) multiple nucl eo-polyhedrovirus (CfMNPV) expressing green fluorescent protein was used to study aspects of nucleopolyhedrovirus infection in the spruce budworm. The temporal and spatial distribution of fluorescence indicated that the virus infected the midgut, entered the tracheal system, and traveled to the epid ermis, fat body, and muscles. In contrast to Autographa californica (Speyer ) (Lepidoptera: Noctuidae) multiple nucleopolyhedrovirus (AcMNPV) infection , hemocytes from infected C. fumiferana ana did nut exhibit fluorescence un til after CfMNPV had passed from the midgut into the tracheae. Therefore th e role of hemocytes may be limited during CfMNPV infection. Also the fluore scence pattern spread from the tracheolar cells to tracheal epithelial cell s throughout the tracheal system. Our results indicate that the temporal an d spatial events involved in CfMNPV infection of C. fumiferana larvae are c onsistent with those observed in other lepidopteran hosts infected with AcM NPV. Minor deviations between these two systems may be attributed to differ ences in virulence, infection rate, and possibly host range of the virus.