Predicting Spruce Weevil Damage in Sitka Spruce in the Northern Oregon Coast Range

Abstract

Abstract The spruce weevil, Pissodes strobi (Peck), is a serious pest of Sitka spruce, Picea sitchensis (Bong.) Carr, in Oregon. Weevils cause damage by killing the leader of a tree, resulting in defects such as crooks and forks that can reduce tree merchantability. In this study,Sitka spruce stands 16–25 years old were surveyed to explore relationships among stand and site characteristics and weevil damage. Trees had an average of 2.8 defects, ranging from 0 to 10, with minor crooks being the most common type of defect. All stands had damage in at least 58% of the trees. The amount of damage was found positively correlated with distance from the ocean and growth rate and negatively correlated with elevation, latitude, and spruce density. These variables together accounted for 61% of variation in the amount of damage.