An individual-based phenology model for western spruce budworm (Lepidoptera: Tortricidae)

An individual-based phenology model for western spruce budworm, Choristoneura occidentalis Freeman (Lepidoptera: Tortricidae), was developed using stage-specific rates of development, oviposition, and egg hatch observed under controlled conditions at several temperatures. Model output was compared with age distributions estimated by sampling field populations of budworm at several locations in British Columbia, Canada, over many years. The fit of the model was very good for the entire life cycle of the insect. We further validate the model by comparing output with independent observations of moth flight phenology of C. occidentalis and Choristoneura fumiferana (Clemens) in populations of Cypress Hills, Canada and illustrate spatial variation in the seasonal occurrence of early-stage feeding western spruce budworm over most of its range in western Canada. In addition to serving as the underlying structure for the modelling of population dynamics at the seasonal level, the model can be used to predict the time of occurrence of different life stages for precise timing of pest management operations.