Abstract
The persistence of Neodiprion sertifer nuclear polyhedrosis virus (NPV) on Pinus contorta foliage samples collected from sawfly infested plantations located throughout Britain was studied. Sawfly density and disease epizootiology varied between localities. Results from the bioassay of branch samples, divided into bark, needle base and foliage samples, indicated that N. sertifer NPV produced during a single virus epizootic can persist for at least 2 years on the pine foliage. Bark and needle base samples were found to be contaminated with NPV more often than foliage samples, perhaps reflecting the effect of weathering on the persistence of virus on the needle surface.