Role of parasites in the population dynamics of the western spruce budworm (Lepidoptera: Tortricidae) in the northwest [Choristoneura occidentalis]

The relation of parasitization to mortality during the generation or from instar IV to adults of western spruce budworm, Choristoneura occidentalis , is examined. Parasitization of budworm larvae and pupae was studied over a wide range of densities (0.3-48.3 larvae per m super(2) and 0.1-22.6 pupae per m super(2)) at sites in Washington, Oregon, Idaho, and Montana. The authors found that parasites contributed about 9% of the variation affecting generation change, and about 24% of variation in mortality during the interval from larvae to adults.