The phenological window for western spruce budworm: seasonal decline in resource quality

Authors

  • Vincent G. Nealis

    Corresponding author
    1. Natural Resources Canada-Canadian Forest Service, Pacific Forestry Centre, 506 W Burnside Road, Victoria, British Columbia V8Z 1M5, Canada
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  • Reproduced with the permission of the Natural Resources Canada, Canadian Forest Service

Vincent G. Nealis. Tel.: +1 250 298 2361; fax: +1 250 363 0775; e-mail: vince.nealis@nrcan-rncan.gc.ca

Abstract

  • 1Western spruce budworm Choristoneura occidentalis Free. (Lepidoptera: Tortricidae) emerge in the spring before budburst and then face a rapidly deteriorating host quality each season.
  • 2Measures of fitness, survival and fecundity, were made on cohorts of final-instar spruce budworms deployed on host trees at several times during the season in four field locations in coastal and interior British Columbia, Canada.
  • 3Survival and fecundity were strongly correlated throughout the season and varied as much as four-fold from maxima at mid-season to minima at the end of the season.
  • 4Fitness values overall were greatest in the coastal compared with interior locations. Among interior locations, fitness was greatest at the highest elevation and least at the lowest elevation. Both cohort and sample-based estimates of survival of wild, final-instar budworms were relatively high in these outbreak populations.
  • 5The influence of the phenological window and degree of synchrony with the host plant on herbivore abundance often depends on other processes affecting population rates of change.

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