Canadian Forest Service Publications
Baculoviruses in populations of western spruce budworm. 2015. Nealis, V.G.; Turnquist, R.; Morin, B.; Graham, R.I.; Lucarotti, C.J. Journal of Invertebrate Biology 127 76-80.
Issued by: Pacific Forestry Centre
Catalog ID: 36088
Available from the Journal's Web site. †
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Population studies of western spruce budworm, Choristoneura occidentalis, revealed that a baculovirus, ChocNPV, was widespread in outbreak populations over a broad geographical area of British Columbia, Canada although the rate of mortality was usually low (<5%). Elevated levels of ChocNPV-related mortality (≈20%) were found when western spruce budworm populations reached high densities (≈300 larvae per kg of Douglas-fir foliage) and contributed to declines in population densities in these areas. A subsample from budworm collections examined using a multiplex-PCR assay showed ChocNPV was the most prevalent virus but also often occurred in combination with a granulovirus, ChocGV and a cypovirus, CoCPV.
Plain Language Summary
Spruce budworms in Canada host several species of naturally-occurring pathogens. Among the most virulent are a group called baculoviruses. Population studies of western spruce budworm reveal that a baculovirus (ChocNPV) was widespread in outbreaks over a wide geographic range in British Columbia. The mortality rate caused by this virus was usually very low (<5%) unless population densities of budworm were extremely high (>30 insects per 45-cm branch tip). Even in those cases where rates of mortality exceeded 20%, the impact on budworm populations was transient. Nonetheless, observed rates of mortality from ChocNPV in western spruce budworm were, in general, higher than observed in the closely related eastern spruce budworm.