Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Past and present outbreaks of the balsam fir sawfly in western Newfoundland: an analytical review.

Abstract

The historical data on defoliation and population density were examined to determine whether a sustained outbreak of balsam fir sawfly (Neodiprion abietis) in western Newfoundland, Canada is unprecedented in severity and duration. In Canada, larvae feed principally on balsam fir (Abies balsamea) and occasionally on white (Picea glauca) and black (P. mariana) spruce. Results indicate that the current outbreak departs substantially from historical trends, covering a surface area twice the sum of all infestations occurring in the preceding 50 years. The current outbreak is also of longer duration due to a northward expansion of the range usually subjected to severe defoliation by this insect. Time-series analysis indicates that balsam fir sawfly dynamics have a strong second-order component, providing testable hypotheses for future studies investigating the factors responsible for population fluctuations.