Epizootiology of a nuclear-polyhedrosis virus in European spruce sawfly,Gilpinia hercyniae: Birds as dispersal agents of the virus during winter

In Welsh spruce forest the relationship of birds to a nuclear polyhdedrosis virus (NPV) was studied outside the larval period of its sawfly host, Gilpinia hercyniae. Birds passed feces containing infective NPV throughout the nonlarval period (November–June). It is thought that birds acquired inoculum by feeding on the corpses of NPV-killed larvae adhering to spruce trees. The proportion of infective droppings declined in the 2 months (May and June) prior to the new larval period. Infective droppings were collected from all six species of birds netted in January. The infectivity of droppings of goldcrest was less and that of longtailed tit greater in January than in the previous September. Experimental evidence suggests that birds may carry NPV for at least 6 km.