Predicting spruce beetle voltinism and flight time in western Canada using a model developed in the United States

Abstract

The ability to predict voltinism and key phenological events such as flight time for forest pests can inform management decisions and aid in assessing the effect of climate change on outbreak risk. We assessed the performance of the spruce beetle voltinism model (Hansen et al. 2001b), which was developed using data from whole standing trees in Colorado, Utah, and Alaska, against observations from field sites in British Columbia, Alberta, and Yukon to determine its potential for use in western Canada. Modifications were also made to the model interface in BioSIM, a software tool for running temperature-driven phenological models, which give users the option to adjust model assumptions and predict univoltinism at six different height-aspect combinations on standing trees. Predicted and observed univoltinism were similar and the modifications to the interface facilitate using the model to predict univoltinism in downed trees based on the output for ground level, north aspect on standing trees. For the period 2021-2050, the voltinism model predicts a high probability of univoltinism in downed trees east of the Rocky Mountains and parts of central and southern British Columbia, which could facilitate outbreaks following wind events or other disturbances. Predictions of peak flight time were usually close to those observed, but there were several differences of 3-4 weeks. The spruce beetle voltinism model developed by Hansen et al. can be used to predict peak flight date and univoltinism in standing and downed trees in western Canada with some caveats and local knowledge.