Balsam Woolly Aphid Infestation of Fraser Fir in the Great Smoky Mountains

The balsam woolly aphid (Adelges piceae (Ratz.)) has within the last decade become a serious pest on Fraser fir (Abies fraseri (Pursh.) Poir.) in the Great Smoky Mountains National Park, causing concern for the scenic and scientific resources of the spruce-fir forests. In order to determine and anticipate the nature and impact of the balsam woolly aphid in this area, a research project was designed to investigate some of the relevant biotic factors.

Objectives of this study were: (1) to determine relationships between levels of infestation, as indicated by aphid population and damage on individual trees, the respective size, crown position, age, growth rate, and bark characteristics of these trees, and (2) to determine relationships between levels of infestation and selected site characteristics including slope, elevation, aspect, and ground vegetation.

Permanent plots were located throughout the Park in areas of varying levels of infestation as determined from aerial photographs. Data were collected on individual trees and sites during the summer of 1976.

Individual tree characteristics were important in determining levels of aphid population on a tree and the amount of damage sustained. The most significant characteristic was tree size: large trees supported the heaviest populations while the smallest trees sustained more severe and/or rapid damage.