Spatial propagation in a delayed spruce budworm diffusive model

We investigate the spatial propagation in a delayed spruce budworm diffusive model where and represent, respectively, the incubation and the maturation delays for the spruce budworm. We find the minimal wave speed to determine the existence of traveling wave fronts of the model. More specifically, the model admits traveling wave fronts when ; the model has no traveling wave solutions when . The proofs are based on combining the upper and lower solutions with the approach of Wu and Zou's theorems, the limit arguments, and Laplace transform. The obtained results help us to understand the spreading patterns and the spreading speed of spruce budworm population.