Relationships Between Regional Soils and Foliage Characteristics and Western Spruce Budworm (Lepidoptera: Tortricidae) Outbreak Frequency

Abstract

A study was conducted to determine if there were any relationships between western spruce budworm ( Choristoneura occidentalis Freeman) outbreak frequency and general soil and foliage variables in Idaho and Montana. Soil and foliage data were collected at 80 sites in Idaho and Montana and subjected to a variety of laboratory analyses. Soil samples from areas with high western spruce budworm outbreak frequency had no volcanic ash present, low available moisture, and extractable aluminum compared with other outbreak frequency classes. Current-year budworm host foliage from areas with high outbreak frequency had high sodium and phosphorous levels and low calcium levels. Discriminant functions developed indicated that soil and foliage characteristics, particularly the depth of the volcanic ash mantle, could be used to predict the western spruce budworm outbreak frequency classes. Results will be of value to researchers and forest managers interested in the factors which contribute to western spruce budworm outbreaks.